FR3093603A1 - A method of accelerated browsing of digital content obtained by adaptive progressive download (HAS), manager, media player and corresponding computer program. - Google Patents

Abstract

The invention meets this need by proposing a method for accelerated browsing in digital content, obtained by adaptive progressive downloading by a rendering terminal via a communication network. This navigation method comprises: - obtaining a description file of the digital content, comprising a list of time segments of the content each associated with several encoding rates of the content, - a restitution, at time intervals of duration T, of a thumbnail representing the content at a current browsing position in the content, the thumbnail being extracted from one of the time segments, the current browsing position depending on a browsing speed in the content. According to the invention, such a method comprises a step of determining an encoding rate of the time segment from which the thumbnail representative of the content at the current navigation position is extracted, as a function of a resource constraint obtained by the terminal, and a step of downloading the time segment from which the thumbnail representative of the content at the current browsing position is extracted, at said determined encoding rate. FIGURE 3B

Description

Method for accelerated navigation in digital content obtained by adaptive progressive downloading (HAS), corresponding manager, multimedia stream player and computer program.

The field of the invention is that of digital multimedia content, namely digital audio and/or video content. More specifically, the invention relates to the optimization of accelerated navigation in a digital multimedia content within a rendering terminal, within the framework of the routing of this digital multimedia content according to a technique known as progressive downloading adaptive to the within a local communication network, such as a home network.

With the generalization of high-speed wireless communication and the proliferation of personal equipment of the smart phone or tablet type, the consumption of digital multimedia content, in particular video and/or audio, has increased sharply. Indeed, access to digital content from an Internet type network is possible today, for most of these personal devices, in particular when they belong to a local communication network, such as a home network.

The distribution of digital content on the Internet is often based on client-server protocols of the HTTP (Hyper Text Transfer Protocol) family. In particular, downloading in progressive mode, called progressive adaptive downloading (in English "http Adaptive Streaming" or HAS), of digital content, also called streaming, makes it possible to transport and consume data in real time, i.e. say that digital data is transmitted over the network and returned by the terminal as it arrives. The client terminal, i.e. the personal equipment, receives and stores part of the digital data in a buffer memory before restoring it. This distribution mode is particularly useful when the bit rate available to the user is not guaranteed for the real-time transfer of the video.

Adaptive progressive downloading (HAS) also makes it possible to broadcast and receive data in different qualities corresponding, for example, to different encoding bit rates. These different qualities are described in a parameter file available for download on a data server, for example a content server. When the client terminal wishes to access a content, this description file makes it possible to select the correct format for the content to be consumed according to the available bandwidth or the storage and decoding capacities of the client terminal. This type of technique makes it possible in particular to take into account variations in bandwidth on the link between the client terminal and the content server.

There are several technical solutions to facilitate the distribution of such streaming content, such as the proprietary solutions Microsoft® Smooth Streaming, Apple® HLS, Adobe® HTTP Dynamic Streaming or the MPEG-DASH standard of the ISO/ IEC which will be described below. These methods propose to send the client one or more intermediate description files, also called documents or manifests, containing the addresses of the different segments at different encoding qualities of the multimedia content.

Thus, the MPEG-DASH standard (for English “Dynamic Adaptive Streaming over HTTP”, in French “Dynamic adaptive streaming over HTTP”) is an audiovisual format standard for broadcasting on the Internet. It is based on the preparation of the content in different presentations of variable quality and speed, cut into short segments (of the order of a few seconds), also called “chunks”, or segments. Each of these segments is made available individually by means of an exchange protocol. The protocol mainly targeted is the HTTP protocol, but other protocols (eg FTP) can also be used. Segment organization and associated settings are published in a manifest in XML format.

The principle underlying this standard is that the MPEG-DASH client makes an estimate of the bandwidth available for the reception of segments, and, depending on the filling of its reception buffer, chooses, for the next segment to load , a representation whose bit rate:
- ensures the best possible quality, and,
- allows a reception delay compatible with the uninterrupted rendering of the content.

Thus, to adapt to varying network conditions, particularly in terms of bandwidth, existing adaptive download solutions allow the client terminal to switch from one version of the content encoded at a certain bit rate, to another encoded at a other speed, during the download. Indeed, each version of the content is divided into segments of the same duration. To allow continuous playback of the content on the client terminal, each segment must reach the terminal before its scheduled playback time. The perceived quality associated with a segment increases with the size of the segment, expressed in bits, but at the same time, larger segments require more transmission time, and therefore present an increased risk of not being received in time for continuous playback of content.

The rendering terminal must therefore find a compromise between the overall quality of the content, and its uninterrupted rendering, by carefully selecting the next segment to be downloaded, from among the various encoding rates offered. To do this, there are different algorithms for selecting the quality of the content according to the available bandwidth, which can present more or less aggressive strategies, or more or less secure.

There are many services for viewing this digital content, such as streaming services (in French, streaming, or streaming), video on demand (VOD), delayed broadcast of television programs (Replay) , or Network PVR type offers (for "Network Personal Video Recorder", i.e. a digital content recording service, carried out by the content provider itself rather than at the end user's home).

The use of these services requires in particular the use of a digital multimedia stream player to decode digital content such as a video and/or audio stream received from the service provider, and of a playback terminal associated with the digital multimedia stream player for displaying, for example, the decoded images and/or soundtracks of the video and/or audio stream . In one example, the multimedia stream player is integrated into the rendering terminal such as a tablet, a computer or a telephone of the “Smartphone” type. In another example, the multimedia stream player is integrated into a residential gateway which ensures the routing of the data within the local communication network and the decoding of the digital content, before allowing its reproduction on a reproduction terminal such as a TV. In yet another example, such a multimedia stream player is an HDMI key, such as the CléTV® from Orange®, which can be connected to a television set, or to a set-top box.

In the following, for the sake of simplification, we will assimilate the digital content to a video and the restitution by the client terminal, i.e. the personal equipment, or consumption by the user of the terminal, to a visualization on the screen of the client terminal. . The term rendering terminal will also be assimilated below to the association of the multimedia stream player and the client terminal.

Return terminals generally allow the customer access to a certain number of functionalities, such as a fast forward/backward function, allowing a user to navigate in an accelerated way in the digital content. Thus, when a user watches a video, for example, he has the possibility of quickly accessing a specific location in it by accelerating its restitution by activating the fast forward/backward function, for example via a button on a remote control. associated with the restitution terminal. In another example, the activation of the fast forward/backward function is done via an application dedicated to managing the multimedia stream player when the latter is associated with a client terminal such as a tablet or a smart phone.

After activating the fast forward/backward function, for example when the user is ready to watch the rest of the video, he restarts the normal playback mode of the video, again via a button on the remote control or via the application dedicated. The media stream player then resumes processing the video stream from the current position in the content, selected by the user during accelerated navigation in the content.

In order for the user to be able to easily identify the part of the video that he wishes to view, it is very useful during fast forward/backward to be able to display to the user thumbnails which illustrate the current position of the user in the video stream.

For this, there are currently two main techniques.

The first technique consists in having the content server directly expose thumbnails corresponding to each available video segment. By thumbnail, we mean here, and throughout this document, an image extracted from the video content, the size of which is reduced compared to the original. Such a thumbnail is also called thumbnail, or thumbnail, and in English is generally referred to as a "thumbnail" (literally "thumbnail", in reference to its size).

These thumbnails, created and saved on the content server, can then be retrieved by the rendering terminal: whatever the current position of the user in the content, there is, on the server, a thumbnail representative of the content at this current position, which can be downloaded and displayed to the user. However, this technique is rarely implemented on the servers because it is cumbersome to implement: in fact, it is necessary to create and store as many thumbnails as there are successive images in the content, which consumes resources. In addition, the thumbnails made available by the content server are most often of reduced quality, and are therefore not suitable for full-screen display on the rendering terminal. They are therefore displayed in the form of small thumbnails, above the timeline illustrating the user's navigation in the content (also called in English "timeline"). It can be difficult for the user to identify their current browsing position in the content based on these small, high-quality thumbnails.

The second technique consists, for the restitution terminal, in retrieving certain video segments at the lowest possible encoding rate, corresponding to the current browsing positions in the content. The terminal extracts a thumbnail from it, which is thus created on the fly, in order to display it at the read position cursor. Each segment of video content indeed includes an “I” image, also called an intra image (generally the first image of the time segment), which can be displayed as a thumbnail on the client terminal to illustrate the video stream. Downloading the lower quality segments optimizes their retrieval time. For example, a thumbnail is displayed every second, corresponding to the first intra image of the lowest quality segment associated with the current browsing position in the content.

This technique is simpler to implement, but it does not offer very high fast forward/backward speeds. Indeed, the user remains dependent on the available bandwidth and if he wishes to fast forward in x64 for example, he can be blocked by the segment recovery time.

For example, the user views a video in normal playback and consumes a high quality video stream broadcast in HAS with segment sizes (in English “chunk”) of a duration of 2 seconds. During a fast forward in x64 for example (i.e. the speed of accelerated navigation in the content is 64 times faster than the normal playback speed of the content), the rendering terminal must display a thumbnail every second, to indicate the user his current browsing position in the content. Starting from a current browsing position N, the restitution terminal must then recover the fragment, or "chunk", video which is located 64 seconds "later" in the stream (when it is browsed at normal playback speed ), to extract a thumbnail. Thus, when the segments (in English “chunks”) have a duration of 2 seconds, the restitution terminal must recover the “chunk” which is at position N+32 (32 = x64 / 2 seconds) in less time or equal to 1 second, to ensure the display of a thumbnail every second. We therefore generally recover the "chunk" of lower quality to be sure to recover it in time.

If the restitution terminal takes more than a second to retrieve and extract the image from this “chunk”, it will remain blocked while waiting for the thumbnail. The actual displacement will then not be x64 but less. The fast forward/backward function is therefore simple to implement in this case, but its operation is dependent on the available bandwidth of the local communication network.

There is therefore a need for an accelerated navigation technique (fast forward/backward) in digital content obtained by adaptive progressive downloading (HAS), which does not have these various drawbacks of the prior art. In particular, there is a need for such a technique which allows better optimization of the consumption of network resources, in particular by taking advantage of the technical specificities of progressive adaptive downloading (HAS).

Presentation of the invention

The invention meets this need by proposing a method for accelerated browsing in digital content, obtained by adaptive progressive downloading by a playback terminal via a communication network. This navigation process includes:
- obtaining a description file of the digital content, comprising a list of time segments of the content, each associated with several encoding rates of the content,
- a restitution, at time intervals of duration T, of a thumbnail representing the content at a current browsing position in the content, the thumbnail being extracted from one of the time segments, the current browsing position depending on a content browsing speed.

According to the invention, such a method comprises a step of determining an encoding rate of the time segment from which the thumbnail representative of the content at the current navigation position is extracted, as a function of a resource constraint obtained by the terminal, and a step of downloading the time segment from which the thumbnail representative of the content at the current browsing position is extracted, at said determined encoding rate.

Thus, the invention is based on an entirely new and inventive approach to accelerated navigation in multimedia content.

Indeed, according to the prior art, the illustration of the position in the video stream during the implementation of an accelerated navigation in a content is done by display, at time intervals of fixed duration (generally one second) , of a low-quality thumbnail representative of the content at the current low-quality browsing position regardless of the resource constraints of the local communication network, in order to keep the accelerated browsing speed constant.

Advantageously, the invention proposes to improve the quality of the user's experience, by adapting the encoding quality of the time segment from which the thumbnail is extracted to the resource constraints, in order to ensure the best compromise between quality of the thumbnail to be displayed and constancy of the accelerated navigation speed.

In other words, if the bandwidth of the local communication network allows it, the restitution of a thumbnail of better quality will be preferred if, however, the accelerated browsing speed is maintained. If, however, the conditions do not allow it, then we favor the restitution of a thumbnail of lower quality so as not to disturb the accelerated navigation speed.

According to a particular aspect of the invention, the resource constraint depends on an instantaneous terminal download rate. Such an instantaneous download rate is estimated from a download duration of a time segment from which a restored thumbnail is extracted and a size of the time segment.

Thus, the higher the encoding quality of the time segment to be downloaded, the longer the download time of this segment will be: the accelerated browsing speed therefore risks being impacted if the rendering terminal does not have the necessary resources. to recover and display the thumbnail in a time less than the duration T fixed according to the prior art at 1 second. According to the invention, the quality of the downloaded time segment is adapted so as not to disturb the flow of time in accelerated navigation, or by offering the best quality thumbnail to display.

According to a particular embodiment of the invention, the method comprises a step of determining the duration T between two successive thumbnail renderings, as a function of the resource constraint estimated by the rendering terminal.

Thus, the invention advantageously proposes to further optimize the fluidity of the accelerated navigation, by adapting not only the quality of the rendered thumbnail, but also the refresh rate of the thumbnail display, in the case where the user bandwidth allows. We thus benefit from greater fluidity by optimizing the recovery of time segments during accelerated navigation in the content.

The invention also relates to a computer program product comprising program code instructions for implementing an accelerated navigation method in digital content, as described above, when it is executed by a processor.

The invention also relates to a recording medium readable by a computer on which is recorded a computer program comprising program code instructions for the execution of the steps of the method of accelerated navigation in a multimedia content according to the invention such as described above.

Such recording medium can be any entity or device capable of storing the program. For example, the medium may comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or else a magnetic recording means, for example a USB key or a hard disk. .

On the other hand, such a recording medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means, so that the program computer it contains is executable remotely. The program according to the invention can in particular be downloaded onto a network, for example the Internet network.

Alternatively, the recording medium may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the aforementioned display control method.

The invention also relates to a device for managing accelerated navigation in digital content obtained by adaptive progressive downloading via a communication network. This management system includes:
- a module for obtaining a description file of the digital content, comprising a list of time segments of the content each associated with several encoding rates of the content,
- a restitution module, at time intervals of duration T, of a thumbnail representing the content at a current browsing position in the content, the thumbnail being extracted from one of the time segments, the current browsing position depending on 'a browsing speed in the content,
- a module for determining an encoding rate of the time segment from which the thumbnail representative of the content at the current navigation position is extracted, as a function of a resource constraint obtained by the terminal, and a time segment download module whose the thumbnail representative of the content at the current browsing position is extracted, at the determined encoding rate.

The resource constraint depends for example on an instantaneous download rate of the terminal, which can be estimated from a download duration of a time segment from which a restored thumbnail is extracted and from a size of the time segment.

According to a particular embodiment, the determination module of the management device is capable of determining the duration T between two successive thumbnail renderings, as a function of the resource constraint estimated by the rendering terminal.

Finally, the invention also relates to a multimedia stream player, comprising a device for managing accelerated browsing in digital content as described previously.

The management device, the multimedia stream player and the aforementioned corresponding computer program have at least the same advantages as those conferred by the navigation method in a multimedia content according to the different embodiments of the present invention.

Brief description of figures

Other aims, characteristics and advantages of the invention will appear more clearly on reading the following description, given by way of a simple illustrative example, and not limiting, in relation to the figures, among which:

represents an Internet progressive downloading architecture based on the use of adaptive progressive downloading according to the invention;

schematically illustrates the hardware structure of a real-time multimedia stream player incorporating a device for managing accelerated browsing of the fast forward/backward type according to one embodiment of the invention;

illustrates an example of implementation of a fast forward/backward function of digital content in adaptive progressive download mode by a multimedia stream player of FIG. 2 associated with a client terminal;

represents an example of selection of a segment of digital content during the implementation of a fast forward/reverse function of the digital content in adaptive progressive download mode according to FIG. 3A by the digital stream reader of FIG. 2 ;

schematically illustrates the rendering of a thumbnail within a rendering terminal according to the invention.

Detailed description of the invention

The general principle of the invention consists in finely calculating the next time segment of a digital content to be retrieved according to the user's network conditions, in order to extract therefrom a thumbnail allowing a user to easily identify his navigation position in the content, as part of an accelerated navigation. In particular, the invention is based on the selection of an encoding bit rate quality of a time segment of a digital content to be downloaded, when the user wishes to navigate in an accelerated manner in the multimedia content in order to view a place particular of the latter, and this in particular in the context of digital content downloaded in adaptive progressive download mode (HAS) by a multimedia stream player in real time. This selection makes it possible to optimize navigation in fast forward or rewind in digital content, by making it possible to adapt the encoding bit rate quality of a time segment from which the thumbnail returned to the user is extracted, to variations in bandwidth of the user's local communication network. Thus, if the bandwidth is satisfactory, we can display a thumbnail of better quality to the user, for example in full screen, which improves the perception of the customer, and allows him to better identify where he is in the content. Conversely, in the event of reduced bandwidth, it is thus possible to maintain constant the fast forward/backward speed chosen by the user by adjusting the optimal selection of the time segment from which the thumbnail is extracted.

We now present, in relation to FIG. 1 , an example of a progressive downloading architecture based on the use of adaptive progressive downloading according to the invention.

The terminal 3, for example a smart phone of the "Smartphone" type, the terminal 4, for example a laptop computer, and the terminal 8, for example an HDMI key connected to a television set 5, are in this example located in a network (LAN, 10) controlled by a home gateway 6. The context of the local network is given by way of example and could easily be transposed to an Internet network of the “best effort” type, a company network, etc.

A digital content server 2 is located according to this example in the wide area network (WAN, 1) but it could either be located in the local area network (LAN, 10), for example in the home gateway 6 or any other equipment capable of host such a content server. The content server 2 receives, for example, digital television content channels from a broadcast television network, not shown, and/or videos on demand, and makes them available to client terminals.

The client terminals 3, 4 and 8 can enter into communication with the content server 2 to receive one or more contents (films, documentaries, advertising sequences, etc.). In general, a terminal sends a request to a server, indicating the chosen content and it receives in return a stream of digital data relating to this content. In the context of a local communication network, such a request passes through the network access gateway, for example the residential gateway.

The terminal is suitable for receiving these digital contents in the form of multimedia data and for restoring them. This restitution consists of providing the terminal with the digital content in a form accessible to the user. For example, received data corresponding to a video are generally decoded, then restored at the terminal level in the form of a display of the corresponding video with its associated soundtrack.

It is common, in this client-server context, to use, to exchange data between the client terminals 3, 4 and 8 and the server 2, an adaptive progressive downloading technique, in English “adaptive streaming”, abbreviated as HAS based on the HTTP protocol. This type of technique makes it possible in particular to offer a good quality of content to the user by taking into account the variations in bandwidth which may occur on the link between the client terminal 3, 4 and 8 and the service gateway 6, or between the latter and the content server 2.

Conventionally, different qualities can be encoded for the same content of a channel, corresponding for example to different bitrates. More generally, we will speak of quality to refer to a certain resolution of the digital content (spatial, temporal resolution, level of quality associated with video and/or audio compression) with a certain bit rate. Each quality level is itself cut on the content server into time segments (or “fragments” of content, in English “chunks”, these three words being used interchangeably throughout this document).

The description of these different qualities and the associated temporal segmentation, as well as the content fragments, are described for the client terminal and made available to it via their Internet addresses (URI: Universal Resource Identifier). All of these parameters (qualities, fragment addresses, etc.) are generally grouped together in a parameter file, called the description file. It should be noted that this parameter file can be a computer file or a set of information descriptive of the content, accessible at a certain address.

These fragments or “chunks” comprise a set of data representative of the content. In the example of a video, each “chunk” of the video notably comprises a first image called an “I” image, or intra, and one or more images which can be predicted from this I image by estimation/compensation of movement.

Terminals 3, 4 and 8 have their own characteristics in terms of decoding capability, display, etc. In a context of progressive adaptive downloading, they can adapt their requests to receive and decode the content requested by the user at the quality that suits them best. In our example, if the content is available at bit rates of 512 kb/s (kilobits per second) (Resolution 1, or level 1, denoted D1), 1024 kb/s (D2), 2048 kb/s (D3) and the client terminal has a bandwidth of 3000 kb/s, it can request the content at any rate below this limit, for example 2048 kb/s. In general, “Ci@Dj” denotes the content number i with the quality j (for example the j-th quality level Dj described in the description file).

The service gateway 6 is in this example a home gateway which ensures the routing of data between the extended network 1 and the local network 10, manages the digital contents by ensuring in particular their reception from the network and their decoding thanks to a reader of multimedia stream 9 (not shown), also called a decoder which is assumed here to be integrated into the gateway 6 or the client terminals 3, 4 and 8. Alternatively, the stream reader can be located elsewhere in the extended network 1 or local 10, in particular at the level of an element of the STB (Set-Top-Box) type (not shown) associated with a television.

In this example, to view a content, the terminal 3, 4 or 8 first interrogates the service gateway 6 to obtain an address of the description document 7 of the desired content (for example, C1). The service gateway 6 responds by providing the terminal with the address of the description file 7. In what follows, it will be assumed that this file is a manifest type file according to the MPEG-DASH standard (denoted “C.mpd”) and will refer interchangeably, depending on the context, to the expression “description file” or “manifest”.

Alternatively, this file can be retrieved directly from a local Internet server or external to the local network, or already be on the service gateway or on the terminal at the time of the request.

An example of a manifest file (MPD) conforming to the MPEG-DASH standard and comprising the description of content available in three different qualities (D1 = 512 kb/s, D2 = 1024 kb/s, D3 = 2048 kb/s) of content fragmented is presented in appendix 1 . This simplified manifest file describes digital content in an XML syntax (from the English "eXtended Markup Language"), comprising a list of content in the form of fragments conventionally described between an opening tag (<SegmentList>) and a closing tag (</SegmentList>). Cutting into fragments makes it possible in particular to adapt finely to fluctuations in bandwidth. Each fragment corresponds to a certain duration (“duration” field) with several quality levels and makes it possible to generate their addresses (URL – Uniform Resource Locator). This generation is done in this example using the elements “BaseURL” (“HTTP://server.com”) which indicates the address of the content server and “SegmentURL” which lists the complementary parts of the addresses of the different fragments :
- “C1_512kb_1.mp4” for the first fragment of the “C1” content at 512 kilobits per second (“kb”) in MPEG-4 format (“mp4”),
- “C1_512kb_2.mp4” for the second fragment,
- etc.

Once it has the fragment addresses corresponding to the desired content, the service gateway 6 proceeds to obtain the fragments via a download to these addresses. It should be noted that this download takes place here, traditionally, through an HTTP URL, but could also take place through a universal address (URI) describing another protocol (dvb://monsegmentdecontent for example).

The terminals 3, 4 or the television set 5, for example via its connection to an HDMI key 8 by plugging into its HDMI port, are used to render a video on demand. Subsequently, this television program is referred to as content C1. Such C1 content is described in a manifest file 7.

As a variant, it will be noted that the content C1 can also be a television program broadcast on a deferred basis, or a personal video of the user, or any other multimedia content of fixed duration, for which the invention also applies.

In one example, a user wishes to view multimedia content, such as a video, on his television set 5 connected to an HDMI key 8. The HDMI key 8 is connected via WiFi® directly to the residential gateway 6. Alternatively, the key HDMI 8 could also be connected via WiFi® to another mobile device in the home network, for example laptop 4 or smart phone 3, through which it could access the extended communication network 1.

The HDMI key 8 can also be controlled by the user by means of the smartphone 3, on which a software application for controlling the HDMI key 8 is installed.

The fragments of content obtained by the residential gateway 6 are for example transmitted via WiFi® to the HDMI key 8, which controls their display on the television screen 5, for restitution to the user after decoding by a multimedia stream player 9 integrated into the gateway 6.

FIG. 2 represents an architecture of a multimedia stream player according to one embodiment of the invention, integrated for example into the gateway 6 or into the terminals 3, 4, or 8 of FIG. 1 . As a variant, this stream reader is integrated at the level of an STB type element associated with a television (not shown).

It conventionally comprises memories M associated with a processor CPU. The memories can be of the ROM ( Read Only Memory ) or RAM ( Random Access Memory ) type, or else Flash. The multimedia stream player 9 comprises an HAS adaptive progressive download module able to request a progressive download of one of the contents at one of the qualities offered in a description file 7. This description file 7 can be recorded for example in the memories M of the multimedia stream player 9 or be outside.

The multimedia stream player 9 further comprises a module for fast forwarding/rewinding digital content Fst_FRW in order to allow a user to quickly go to a specific location in the content.

The multimedia stream player 9 also comprises a module for selecting the quality of a fragment, or "chunk", of a content SEL_Q, which drives the adaptive progressive download module HAS, in order to force the latter to request a download a “chunk” of a quality adapted to the bandwidth of the user during the implementation of a fast forward/backward function by the Fst_FRW module. It also includes an Extract_IM extraction module of at least one thumbnail of a selected fragment, which can be rendered on the screen in order to allow the user to know where he is in viewing the content.

The multimedia stream player 9 according to the invention can also contain other modules (not shown) such as a hard disk for storing video fragments, a content access control module, a module for processing commands received from a tablet, a Smartphone, or a remote control, thanks to which the user can control its operation, etc.

It will be noted that the term module can correspond both to a software component and to a hardware component or a set of hardware and software components, a software component itself corresponding to one or more programs or computer or more generally to any element of a program capable of implementing a function or a set of functions as described for the modules concerned. In the same way, a hardware component corresponds to any element of a hardware (or hardware) assembly capable of implementing a function or a set of functions for the module concerned (integrated circuit, smart card, memory card, etc. .).

FIG. 2 only illustrates one particular way, among several possible, of making the stream reader 9, so that it carries out the steps of the method detailed below, in relation to FIGS. 3A and 3B (in any of the different embodiments, or in a combination of these embodiments). Indeed, these steps can be carried out either on a reprogrammable calculation machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated calculation machine (for example a set of logic gates like an FPGA or an ASIC, or any other hardware module).

We now present in relation to FIG. 3A , an example of implementation of a fast forward/backward function in digital content obtained by adaptive progressive downloading (HAS) according to the invention.

In this example, a user wishes to view, in normal reading mode, a digital content, such as a video, on his television set 5 connected to an HDMI key 8 incorporating a multimedia stream player 9 according to FIG . The multimedia stream player 9 comprises a module SEL_Q for selecting an encoding bit rate, or quality, Dj, of a fragment of the content, an HAS module and an Extract_IM module for extracting at least one thumbnail from the selected fragment. The HDMI 8 dongle can be controlled via a remote control or via a smart phone control software application 3.

In order to view a video, the user, via the restitution terminal 30, i.e. association of the television set 5 and the HDMI key 8 forming a stream reader 9, sends during a step 301 a request, which passes through the gateway 6, indicating the chosen content to the “HAS” content server 2.

Still during this step 301, in normal reading mode, the “HAS” content server 2 sends in response to this request a data stream representative of the chosen content. The "HAS" content server 2 exposes a video C1 in the form of fragments, or "chunks" C1 _i @Dj encoded at different encoding bit rates Dj, where the index i denotes a temporal identifier, or position, of the "chunk » C1 _i @Dj.

This data stream is recovered by the HAS module of the multimedia stream player 9, for example the HDMI key 8 which controls the restitution on the television set 5 for viewing by the user.

According to the prior art, the HAS module is responsible for recovering the “chunks” from the “HAS” content server 2 by choosing the video quality Dj according to the available network resource. We will not describe here in more detail the way in which the HAS client module chooses the encoding rate of the next video fragment to be downloaded: there are indeed many algorithms allowing this choice to be made, whose strategies are more or less secure. or aggressive. It is recalled, however, that, most often, the general principle of such algorithms is based on the downloading of a first fragment at the lowest encoding rate proposed in the manifesto, and on the evaluation of the recovery time of this first fragment. . Based on this, the HAS client module assesses whether, based on the size of the fragment and the time taken to retrieve it, the network conditions allow the next fragment to be downloaded at a higher encoding rate. Some algorithms rely on gradually increasing the quality level of downloaded content fragments; others propose more risky approaches, with jumps in the levels of the encoding bit rates of the successive fragments.

In a typical case, if a video “chunk” lasts 2 seconds, the recovery of the “chunk” by the HAS module must not exceed 2 seconds, in order to allow uninterrupted playback of the content. It is therefore appropriate for the HAS module to operate the best compromise between a restitution quality, and therefore an encoding bit rate, as high as possible, and the download time of the fragment, which must be sufficiently low to allow restitution in continuously on the TV 5 for example.

During a step not shown, the HAS module retrieves the manifest file 7 in order to discover the available fragments of the video content C1, and the various associated video qualities Dj. In an example illustrated below in relation to FIG. 3B , the content C1 is for example offered in the form of fragments of duration 2s, with a first encoding rate D1 = 500 kb/s, a second encoding rate D2 = 1000 kb/s, a third encoding rate D3 = 2000 kb/s, etc.

In a normal mode of operation, not illustrated, the HAS module performs the downloading, for example, of successive fragments C1 ₁ @D1 (i.e. the first temporal fragment at an encoding rate of 500 kb/s), then C1 ₂ @D3 (i.e. the second time fragment at an encoding rate of 2000 kb/s), then C1 ₃ @D3 (i.e. the third time fragment at an encoding rate of 2000 kb/s), then finally until a playback in normal mode in high quality of a C1i@D5 video (i.e. the i-th temporal fragment at an encoding rate of 5000kb/s).

The various fragments downloaded by the HAS client module are transmitted to the television set 5 via the HDMI key 8 for example for their restitution to the user.

The algorithm implemented by the HAS client module to determine which fragment at which encoding rate must be downloaded in normal operating mode (i.e. outside the periods when it is controlled by the SEL_Q module of selection of the quality of a fragment) can be one of the already existing algorithms of the prior art. This algorithm will therefore not be described here in more detail.

When the user is viewing digital content such as a video in normal playback mode, the user can use the fast forward/reverse function at any time. Thus, in a step 302, the FST_FRW module of the multimedia stream player 9 receives a command for activation by the user of a fast forward/backward function in the content, with a selection of an acceleration speed, by example x64, which is an accelerated speed sixty-four times faster than the normal playback speed of the content. This activation command is made by the user via, for example, a software application for controlling the HDMI key 8, a smart telephone 3, or via a remote control connected to the HDMI key 8 connected to the television set 5. In response to this command, the Fst_FRW module increases the browsing speed in the content.

In a step 303, the module SEL_Q of the multimedia stream player 9 will select a “chunk” at a position i in the video content C1 corresponding to a ratio of the speed A of accelerated navigation in the video C1 over the duration D of the “ chunk”. The SEL_Q module then commands the HAS module to retrieve the selected fragment.

For example, the user chooses to navigate in a video with an accelerated navigation speed x64, ie sixty-four times faster than the normal reading speed of the content. It is assumed that this video is cut into “chunks” of identical durations, equal to 2 seconds. Starting from a current navigation position associated with the segment of rank N, the HAS module of the multimedia stream player 9 will therefore recover in a step 304 the “chunk” in position i=N+32 (x64/2=32), then the “chunks” following all the N+32n-th positions (for example, the “chunk” following the N+32 will be the N+64 etc…) . For this, as for step 301, a request from the HAS module to the HAS server 2 is sent. In response to this request, the HAS server 2 sends the restitution terminal 9 the fragments chosen by the module SEL_Q.

Thus, in order to be able to make it easier for the user to identify his current browsing position in the digital content, a thumbnail representing the content at this current browsing position is displayed on the digital content restitution terminal. Since each segment of video content includes an “I” frame, usually the first frame of the time segment, this intra frame can be displayed as a thumbnail on the client terminal to illustrate the video stream.

An example of display of a thumbnail I , for example on the television set 5, at regular time intervals, for example every second, is presented in connection with FIG. The display of the thumbnail is done for example on the entire screen of the television set 5 for better viewing by the user.

In a variant, the display of the thumbnail is done at the level of the playback position cursor Cr on the timeline TL.

For this, in a step 305 illustrated in FIG. 3A , the extraction module EXTRACT_IM of the multimedia stream player 9 extracts a thumbnail of the “chunk” selected and retrieved in step 303.

The extracted thumbnail can correspond for example to the first “I” image of the selected fragment. The extracted thumbnail is then displayed on the television 5 so that the user knows where he is in viewing the video content C1. The time necessary for the restitution of the thumbnail depends on the encoding quality of the fragment selected in step 303 and on a downloading time of the fragment. Thus, the higher the quality of the fragment, the longer the time required for downloading and restoring the thumbnail. In what follows, this time will be called T _res .

In a first embodiment of the invention, it is considered that when the accelerated navigation in the content is initialized, a thumbnail corresponding to the current navigation position in the content is displayed at regular time intervals of duration T=1s.

It is then necessary to be able to recover the thumbnail representing the current navigation position in the content in less than T=1s (or in a maximum time of T=1s), to allow continuous visualization of the thumbnails by the user, consistent with the accelerated navigation speed A that he has chosen.

In a step 306, the module SEL_Q of the multimedia stream reader 9 therefore selects, as a function of a time T _res of restitution of a thumbnail, which corresponds to the download time of a first fragment, for example C1 _N+32 , and display of the first “I” image of the segment, the next fragment to be downloaded to be as close as possible to the acceleration speed chosen by the user, in this example x64. In the same way, for each current fragment downloaded and for each restitution of the corresponding thumbnail, the module SEL_Q determines which will be the next fragment to be downloaded according on the one hand to the accelerated browsing speed A chosen by the user and of the duration D of the fragments of the video content C1, and on the other hand of the time T _res necessary for the restitution of a thumbnail.

In other words, under the control of the SEL_Q module, the HAS module chooses the encoding rate of the next video fragment to be downloaded from which the next thumbnail to be displayed will be extracted. There are many algorithms for making this choice, whose strategies are more or less secure or aggressive. It is however recalled that, most often, the general principle of such algorithms is based on the downloading of a first fragment at the lowest encoding rate proposed in the manifesto, and on the evaluation of the recovery time of this first fragment. . Based on this, the HAS client module evaluates whether, based on the size of the fragment and the time taken to retrieve it, the network conditions allow the next fragment to be downloaded at a higher encoding rate. Some algorithms rely on gradually increasing the quality level of downloaded content fragments; others propose more risky approaches, with jumps in the levels of the encoding bit rates of the successive fragments.

Such algorithms can be adapted to the fast forward/backward function of a multimedia stream player so that they take into account parameters of acceleration speed and playback frequency.

Thus, if the bandwidth is satisfactory, and if the rendering terminal has a high instantaneous download rate, it is possible to download a time segment associated with a higher encoding rate, which will make it possible to render to the user a thumbnail of better visual quality. The encoding rate of the time segments that are downloaded is thus permanently adapted to extract the thumbnails, depending on the resource conditions of the user terminal.

We now present, in relation to FIG. 3B , an example of selection 306 of the quality of a fragment according to the bandwidth of a local communication network during the implementation of a fast forward/backward function digital content downloaded in adaptive progressive download (HAS) by a multimedia stream player 9 according to FIG .

In this example, the user views video content broadcast in HAS with sizes of fragments, or “chunks”, of the same duration D, for example 2 seconds, in normal playback mode. The video stream consumed is of high quality, for example 5000 kb/s (D5) as illustrated in FIG. 3A .

At the position i=N, corresponding to a particular instant of the video content represented by the fragment C1 _N @D5, the user decides to navigate in accelerated mode in the video content C1, for example at the accelerated navigation speed A of x64.

The first “chunk” that is recovered is the “chunk” at position i = N + A/D, i.e. i = N + 32 (where 32 = x64 / 2s). By default, the first "chunk" to be recovered by the HAS module, under the control of the SEL_Q module, is of lower quality than the quality reached in normal playback mode, in this example the D5 quality, in order to recover the first thumbnail to be returned as soon as possible (typically the lowest quality available according to the manifest).

For each fragment to be recovered, the module SEL_Q of the multimedia stream reader 9 initially compares the time T _res necessary for the restitution of the thumbnail I to the duration T of the time interval between two restitutions of successive thumbnails to determine if the next fragment to be retrieved can be of higher quality or should be of lower quality than the current fragment just downloaded. The time T _res for restoring a thumbnail is dependent on the bandwidth of the local communication network. A time T _res greater than the duration T indicates that the bandwidth is not sufficient and that it is therefore necessary to give preference to the recovery of a following fragment of lower quality with respect to the current fragment. Conversely, a time T _res less than the duration T indicates that the bandwidth is sufficient to recover a following fragment of better quality compared to the current fragment.

In this example, the maximum image restitution time T _res must not exceed 1 second, in order to have a fluid flow of the digital content in accelerated navigation mode .

Thus, the first chunk that is downloaded is the lowest quality chunk at position i = N + 32 (32 = x64 / 2s), i.e. the chunk at position C1 _n+32 @D1. We managed to render this thumbnail of the video in less than 1 second. The thumbnail can then be displayed to the user without disturbing the passage of time in accelerated reading mode at the speed of x64. The following fragment located at position i=N+32, or i=N+64, may in this case be chosen with a higher quality than that of the fragment C1 _N+32 @D1, if the time difference allows it. Thus, the next “chunk” downloaded is for example the C1 _n+64 @D4. In this way, it is possible to display a thumbnail of better quality to the user.

If we do not succeed in restoring the thumbnail of the first "chunk" in a restitution time T _res of 1 second, because the bandwidth of the user's local communication network does not allow it, we will therefore have a flow time which will be slowed down in relation to the x64 accelerated browsing speed chosen by the user, and the user will have to wait for the thumbnail to be available in order to be displayed, which is detrimental to his comfort. In this case, if the first “chunk” to be recovered at position i = N+32 is not the one with the lowest quality, i.e. for example the “chunk” C1 _n+32 @D3, then the SEL_Q module will select the next "chunk", i.e. the one in position i = N+32 or i = N+64, of a lower quality, for example C1 _n+64 @D2 hoping recover it in less than 1 second.

In another embodiment according to the invention, it is also possible to act, not only on the encoding rate of the time segment from which the thumbnail to be restored is extracted, but also on the duration of the time interval between the restitution of two successive thumbnails, according to the resource constraints of the local network.

Thus, in this variant, the duration T of the time interval between two successive thumbnail renderings is no longer fixed but can be adapted according to the available bandwidth, either to display more thumbnails to the user per second, if the conditions are good, or to space out the restitutions of successive thumbnails.

In the example described, if we do not succeed in restoring the thumbnail of fragment C1 _N+32 @D1 in this time interval of 1 second duration, then in this case, in order to ensure a passage of time as close as possible to what is requested by the user, the SEL_Q module determines which is the next “chunk” to download. In this example, the maximum restitution time T _res to recover a thumbnail without disturbing the flow of the viewing time in accelerated reading mode in x64 is 1 second. If we download the fragment C1 _N+32 @D1 and we extract the thumbnail in for example T = 1.25s, then the next "chunk" that we will decide to download will be at position i = T* (A /D), i.e. i = 1.25 x 64/2 = 40. We therefore download the "chunk" at position i = N+40 and not i = N+32 in order to guarantee a flow of fast forward the as close as possible to x64, i.e. the C1 _n+40 @D1 chunk.

More generally, the HAS module can act jointly on the encoding rate of the time segments to be downloaded, and on the frequency of restitution of the thumbnails, according to the resource constraints of the network, to offer the user the best browsing experience. accelerated in content.

APPENDIX 1: sample manifest file

Claims (11)

Method for accelerated browsing in digital content, obtained by adaptive progressive downloading by a rendering terminal via a communication network, comprising:
- obtaining a description file of said digital content, comprising a list of time segments of said content each associated with several encoding bit rates of said content,
- a restitution, at time intervals of duration T, of a thumbnail representing said content at a current browsing position in said content, said thumbnail being extracted from one of said time segments, said current browsing position depending on a speed navigation in said content,
characterized in that it comprises a step of determining an encoding rate of said time segment from which said thumbnail representative of said content is extracted at said current navigation position, as a function of a resource constraint obtained by said terminal, and a step of downloading said time segment from which said thumbnail representative of said content is extracted at said current navigation position, at said determined encoding rate. Accelerated navigation method according to Claim 1, characterized in that the said resource constraint depends on an instantaneous download rate of the said terminal. Accelerated navigation method according to Claim 2, characterized in that the said instantaneous downloading rate is estimated from a duration of downloading of a time segment from which a restored thumbnail is extracted and from a size of the said time segment. Accelerated navigation method according to any one of Claims 1 to 3, characterized in that it also comprises a step of determining the said duration T between two successive thumbnail restitutions, as a function of the said resource constraint obtained by the said terminal of restitution. Computer program product comprising program code instructions for implementing an accelerated navigation process in digital content, obtained by adaptive progressive downloading by a rendering terminal via a communication network according to any of claims 1 to 4, when executed by a processor. A computer-readable recording medium on which a computer program according to claim 5 is recorded. Device for managing accelerated browsing in digital content, obtained by adaptive progressive downloading by a rendering terminal via a local communication network, said management device comprising:
- a module for obtaining a description file of said digital content, comprising a list of time segments of said content each associated with several encoding rates of said content,
- a restitution module, at time intervals of duration T, of a thumbnail representing said content at a current browsing position in said content, said thumbnail being extracted from one of said time segments, said current browsing position depending on a browsing speed in said content,
characterized in that itunderstand additionally a module for determining an encoding rate of said time segment from which said thumbnail representative of said content is extracted at said current navigation position, as a function of a resource constraint estimated by said terminal, and a download module of said time segment from which is extracted said thumbnail representative of said content at said current browsing position, at said determined encoding rate. Device for managing accelerated browsing in digital content according to Claim 7, characterized in that the said resource constraint depends on an instantaneous download rate of the said terminal. Device for managing accelerated browsing in digital content according to Claim 8, characterized in that the said instantaneous downloading rate is estimated from a downloading duration of a time segment from which a restored thumbnail is extracted and of a size of said time segment. Device for managing accelerated browsing in digital content according to any one of Claims 7 to 9 , characterized in that the said determination module is able to determine the said duration T between two successive thumbnail renderings, as a function of the said resource constraint. estimated by said rendering terminal. Multimedia stream player, characterized in that it comprises a device for managing accelerated browsing in digital content (C1) according to any one of Claims 7 to 10.