JP5267542B2 - Encoded video signal conversion method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transcoding method and device capable of obtaining a high-quality image and reducing the amount of arithmetic processings necessary for transcoding. <P>SOLUTION: A recording and reproducing device 100 includes an encoder 101, a transcoder 102, an intermediate information storage memory 105, a stream storage memory 106, a compression and decompression means 107, an input image storing memory 108 and a user interface 110. When encoding by a second compression coding method is performed in the encoder 104, intermediate information is read out of the intermediate information storing memory 105 and then is processed into a usable format which is to be used for encoding by a second compression coding method. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention relates to a coding method and a conversion method and device for converting a bit rate of a coded video signal coded by a certain coding method.

Due to the rapid development of moving image processing technology in recent years, a wide variety of objects and devices handle moving images. In addition, since the amount of moving image data is generally very large, when a moving image as digital data is handled, it is generally used after being compressed and encoded.

Conventionally, compression encoding according to the purpose of use and the target device has been used, but for the purpose of sharing data between different devices, moving image data compressed and encoded by a certain encoding method is different. Transcoding is performed to convert to a conversion method. In addition, the compression encoding method is not changed, and the size and frame rate of a moving image are changed, or the compression rate is increased to convert to a bit rate suitable for the application.

For such conversion, a method of once decoding the conversion source bit stream and then re-encoding it in a desired encoding format is adopted. At that time, in order to reduce the load of the conversion process, intermediate information at the time of transcoding is used. There has been proposed a method of performing re-encoding using (see Patent Document).

JP 2003-264840 A JP 2003-116104 A JP 2003-61089 A JP 2002-320228 A JP 2001-268578 A

However, in the above-described conventional transcoding, the first frame is decoded, and the intermediate information obtained at the time of the first decoding is immediately used for encoding the first frame. The intermediate information of the second and third frames that have not been used cannot be used for encoding the first frame.

An object of the present invention is to provide a method and apparatus for making it possible to use intermediate information of second and third frames when re-encoding transcoding of a first frame.

An encoded video signal conversion method for converting a first encoded video signal into a second encoded video signal, wherein an input signal is compressed using a first compression encoding method, and the first compression encoding method is used. The encoding intermediate signal generated before converting the compressed encoded video signal by the second compression encoding method is stored, and the encoded video signal converted by the first compression encoding method is subjected to the second compression encoding. When converting to a method,
The stored encoded intermediate information is used.

  High-quality transcoding and rate conversion can be realized.

It is the figure which showed the 1st Embodiment of this invention. It is the figure which showed the 2nd Embodiment of this invention. 3 is a diagram showing an internal configuration of an encoder 104. FIG. It is the figure which showed the 3rd Embodiment of this invention. 10 is a flowchart showing a flow of determination in intermediate information use / non-use determination means 1043.

  The configuration according to the first embodiment of the present invention is shown in FIG.

The video recording / playback apparatus converts the input digital video signal into a first compression encoding method (for example, M
PEG2) is compressed into a first encoded video signal and recorded in a storage such as a hard disk. Also, the first encoded video signal is decoded and a second compression encoding method (for example, MP
Stream conversion is realized by encoding with EG4).

The recording / reproducing apparatus 100 includes an encoder 101, a transcoder 102, an intermediate information storage memory 105, a stream storage memory 106, and a user interface 110. The user interface 110 is not essential and the user can use the transcoder 102.
Used as an interface for controlling the operation of The intermediate information storage memory 105 and the stream storage memory 106 may be configured by independent storage media, or may be configured by the same storage media.

The encoder 101 encodes a digital video signal input from the outside of the recording / reproducing apparatus 100 using the first compression encoding method, and outputs a first encoded video signal. The output first encoded video signal is output to the stream storage memory 106 and stored. Further, intermediate information generated when the encoder 101 encodes a digital video signal input from the outside is output to the intermediate information storage memory 105 and stored therein. Here, the intermediate information refers to a motion vector, a quantization value or a quantization scale obtained at the time of encoding, a statistical value of a luminance change between temporally preceding and succeeding frames, a temporal transition of a bit rate, and the like.

The transcoder 102 includes a decoder 103 and an encoder 104. The first encoded video signal read from the stream storage memory 106 is supplied to the decoder 103. The decoder 103 decodes the supplied first encoded video signal and outputs a digital video signal. The decoder 103 has a function of changing the image size and frame rate of the decoded digital video signal, and the digital video signal output from the decoder 103 is the same as that obtained by decoding the first encoded video signal. There are cases where the image size and frame rate are used, and there are cases where the image data is scaled to an appropriate size inside the decoder 103 or adjusted to an appropriate frame rate. The encoder 104 encodes the digital video signal output from the decoder 103 by the second compression encoding method, and outputs a second encoded video signal. Here, the intermediate information storage memory 105 stores intermediate information when encoding is performed using the first compression encoding method, and when the encoder 104 performs encoding using the second compression encoding method. Is used when the intermediate information is read from the intermediate information storage memory 105, processed into a usable format, and encoded by the second compression encoding method.

For example, when the second compression encoding method is MPEG4, a large calculation amount is required to obtain a motion vector at the time of encoding. Further, in order to obtain the motion vector, the pixel values of the previous and subsequent frames are necessary, and it is necessary to secure a memory for holding the pixel values. In this method, a motion vector, which is intermediate information when compressed by the first compression encoding method, is read from the intermediate information storage memory, and this is adapted to the image size and frame rate when performing the second compression encoding. In this way, scaling, fine adjustment, etc. are performed and used for the second compression encoding. By this method, it is possible to reduce the amount of calculation for obtaining the motion vector and save the frame holding memory.

In another example, the bit rate control when performing the second compression coding using the statistics of the temporal change of the luminance value, which is the intermediate information when compressed by the first compression coding method. Can also be used. Specifically, a method of performing rate control so that a high-quality image is visually obtained by allocating a code amount to a portion with a small luminance change without allocating a large code amount to a portion with a large luminance value change. There is.

In another example, a quantization value or a quantization scale when compressed by the first compression encoding method,
Alternatively, it is possible to control the bit rate when performing the second compression encoding using the transition of the bit rate. In this embodiment, since there is already intermediate information generated when encoding an externally input video signal, more optimal bit rate control can be performed by feeding back bit rate transitions and quantization value transitions. It is also possible to do. This
It is possible to control the rate so that the bit rate transition at the time of compression by the first compression encoding method follows without delay.

The transcoder 102, the decoder 103, and the encoder 104 can be controlled from the user side via the user interface 110 so as to perform a desired operation. Specifically, the bit rate setting of the encoder 104, the output image size of the decoder 103, the frame rate, and the like can be set.

The first compression encoding method and the second compression encoding method described above may be the same method,
Different schemes may be used.

The encoder 101 and the encoder 104 may be partly or wholly shared.

Also, the intermediate information when compressed by the first compression encoding method may be recorded at the time of encoding, or when the set bit rate at the time of encoding exceeds a certain threshold, that is, encoded with high image quality. Only in some cases, the intermediate information may be recorded. Using the user interface 110,
The user may specify whether or not to record the intermediate information.

  A configuration according to the second embodiment of the present invention is shown in FIG.

The video recording / playback apparatus converts the input digital video signal into a first compression encoding method (for example, M
PEG2) is compressed into a first encoded video signal and recorded in a storage such as a hard disk. At the same time, the input digital video signal itself is recorded in the storage with or without compression. Further, the stream conversion is realized by encoding the digital video signal obtained by decoding the first encoded video signal or the digital video signal recorded in the storage by the second compression encoding method (for example, MPEG4).

The recording / reproducing apparatus 100 includes an encoder 101, a transcoder 102, an intermediate information storage memory 105, a stream storage memory 106, a compression / decompression unit 107, and an input image storage memory 108.
The user interface 110 is configured. The user interface 110 is not essential and is used as an interface when the user controls the operations of the transcoder 102 and the compression / decompression unit 107. The intermediate information storage memory 105, the stream storage memory 106, and the input image storage memory 108 may be configured by independent storage media, or may be configured by the same storage media.

Since the operations of the encoder 101, the intermediate information storage memory 105, and the stream storage memory 106 are the same as those in the first embodiment of the present invention, description thereof is omitted here.
The input digital video signal supplied to the encoder 101 is also supplied to the compression / expansion means 107 at the same time. The compression / decompression unit 107 stores the input digital video signal in the input image storage memory 108 without being compressed or after being compressed by a certain compression method. Here, the compression method is a method of entropy encoding a difference between pixel values from the previous frame, a method of entropy encoding a difference from the left pixel value, a lossless compression method such as LZH or ZIP, JPEG, GIF , PNG
Any of the irreversible compression methods may be used.

Also, a mechanism may be provided in which characteristics of the input digital video signal are determined by an analysis means such as a filtering operation, and an appropriate compression method is selected according to the characteristics. For example, a Sobel filter operation for edge extraction is performed on an input digital signal, and an image having a large number of edge detection points, that is, an image having a large number of places with sharp changes in luminance, adopts a compression method such as GIF or PNG, For a small image, that is, an image with a smooth luminance change, a switching mechanism may be incorporated such that compression is performed by the JPEG method.

Further, selection of compression / non-compression, selection of a compression method, selection of a compression rate, and the like when the input digital video signal is stored in the input image storage memory 108 can be controlled by the user via the user interface 110.

During the transcoding operation, the input digital video signal stored in the input image storage memory 108 is read by the compression / expansion means 107, and if the signal is compressed, it is expanded,
It is supplied to the encoder 104. When the signal is uncompressed, it is supplied to the encoder 104 as it is. Here, the compression / decompression unit 107 has a function of changing the image size and frame rate of the input digital video signal, and the digital video signal output from the compression / decompression unit 107 decodes the first encoded video signal. In some cases, the image size or the frame rate is kept as is, and the compression / expansion means 107 scales the data to an appropriate size.
The frame rate may be adjusted to an appropriate value.

Since the operation of the decoder 103 included in the transcoder 102 is the same as that of the first embodiment of the present invention, description thereof is omitted here.

The configuration of the encoder 104 is shown in FIG. The encoder 104 includes input switching means 104.
1 and an encoding unit 1042 and intermediate information use / non-use determination unit 1043.
The input switching means 1041 is supplied with the input digital video signal supplied from the compression / expansion means 107 and the decoded digital video signal supplied from the decoder 103, and is appropriately switched and output to the encoding means 1042. The input switching control can be directly controlled by the user via the user interface 110.

The encoding unit 1042 encodes the digital video signal supplied from the input switching unit 1041 using the second compression encoding method, and outputs a second encoded video signal. Here, the intermediate information storage memory 105 stores intermediate information when encoding is performed using the first compression encoding method, and when the encoder 104 performs encoding using the second compression encoding method. Is used when the intermediate information use / non-use determination means 1043 reads the intermediate information from the intermediate information storage memory 105, processes it into a usable format, and encodes it with the second compression encoding method. Since this specific example is the same as that of the first embodiment of the present invention, a description thereof will be omitted.
The intermediate information use / non-use determination unit 1043 switches between performing encoding using the intermediate information and performing encoding without referring to the intermediate information. Switching can be controlled from the user side via the user interface 110.

Here, considering the case where the input digital video signal is handled by the compression / expansion means 107 in a non-compressed or lossless compression mode, the input digital video signal supplied from the compression / expansion means 107 is selected by the input switching means 1041. In this case, since the digital video signal supplied to the encoding unit 1042 has no image quality deterioration due to compression / expansion, it is possible to realize transcoding with very high image quality. Further, as described in the first embodiment of the present invention, the amount of processing required for transcoding can be reduced by using the data stored in the intermediate information storage memory 105.

Also, a mechanism is provided for determining whether or not the intermediate information when compressed by the first compression encoding method exists in the intermediate information storage memory 105 and recording the intermediate information only when the intermediate information does not exist. May be.

  The configuration according to the third embodiment of the present invention is shown in FIG.

In the present embodiment, the first encoded video signal encoded by the first encoding method input to the recording / reproducing apparatus is decoded and encoded by the second encoding method. Generate a video signal.

The recording / reproducing apparatus 100 includes a transcoder 102, an intermediate information storage memory 105, display means 109, and a user interface 110.

The first encoded video signal is external to the recording / reproducing apparatus 100, for example, the stream storage memory 1
06 and supplied to the transcoder 102. In addition to the above, the first encoded video signal may be supplied from an external storage such as a DVD medium or the Internet.

The transcoder 102 includes a decoder 103 and an encoder 104.
The first encoded video signal read from the stream storage memory 106 is sent to the decoder 103.
To be supplied. The decoder 103 decodes the supplied first encoded video signal and outputs a digital video signal. The decoder 103 has a function of changing the image size and frame rate of the decoded digital video signal, and the digital video signal output from the decoder 103 is the same as that obtained by decoding the first encoded video signal. There are cases where the image size and frame rate are used, and there are cases where the image data is scaled to an appropriate size inside the decoder 103 or adjusted to an appropriate frame rate. The decoder 103 also outputs intermediate information extracted from the first encoded video signal at the time of decoding,
It is stored in the intermediate information storage memory 105. Here, the intermediate information is a motion vector extracted from the first encoded video signal at the time of decoding, a quantization value or a quantization scale, a statistical value of a luminance change between frames before and after, a bit rate Refers to temporal transitions. In this embodiment, the decoder 103 is treated as a component of the transcoder 102. Instead, a decoder is connected to the outside of the transcoder 102, and the first encoded video signal is decoded using this decoder. It is good.

The encoder 104 encodes the digital video signal output from the decoder 103 by the second compression encoding method, and outputs a second encoded video signal. Here, the intermediate information storage memory 1
05 stores intermediate information extracted from the first compression-coded signal.
When the second compression encoding method is used in 04, the intermediate information is read from the intermediate information storage memory 105, processed into a usable format, and encoded by the second compression encoding method. Sometimes use. Since this specific method is the same as that of the first embodiment of the present invention, description thereof is omitted.

The decoder 103 decodes the first compressed encoded signal, extracts intermediate information at the same time, and writes the intermediate information in the intermediate information storage memory 105 at an arbitrary timing. For example, the first compressed code stored in the stream storage memory 106 The intermediate information may be stored in the background where the digitized signal is decoded and reproduced and displayed via the display means 109, or the display means 10
It is also possible to extract only the intermediate information without displaying it by 9. Alternatively, the idling state in which the user does not perform any operation may be automatically determined, and the intermediate information may be extracted and stored in the background.

In particular, when playback / display is not performed, the system may perform decoding as fast as possible to extract and store intermediate information.

Since it is unclear whether the intermediate information of the stream to be transcoded exists in the intermediate information storage memory 105, the encoder 104 has a function of determining whether the intermediate information of the stream to be transcoded exists in the intermediate information storage memory 105. The structure provided may be sufficient. In this configuration, if there is intermediate information as a result of the determination, transcoding is performed using the intermediate information. If there is no intermediate information, encoding may be performed without using the intermediate information, or transcoding may be performed using the intermediate information after automatically generating the intermediate information. Furthermore, the configuration may be such that the intermediate information use / non-use determination unit in FIG. 3 is selected and the user is allowed to select use / non-use of the intermediate information. The above determination flow is shown in FIG.
As an application example of this embodiment, when transcoding is performed, it is sufficient that intermediate information for data desired to be transcoded is prepared in advance, and further, decoding at the time of transcoding is performed by re-encoding. By performing several to several tens of frames ahead of the frame, future intermediate information can be used, and for example, it is possible to follow the bit rate transition without delay.

DESCRIPTION OF SYMBOLS 100 ...... Recording / reproducing apparatus 101 ...... Encoder 102 ...... Transcoder 103 ...... Decoder 104 ...... Encoder 1041 ...... Input switching means 1042 ...... Encoding means 1043 ...... Intermediate information use / non-use determination means 105 ...... Intermediate information Storage memory 106 ...... Stream storage memory 107 ...... Compression / expansion means 108 ...... Input image storage memory 109 ...... Display means 110 ...... User interface

Claims (5)

An encoding device that encodes an input signal using a first encoding method and a second encoding method,
A first encoder that encodes the input signal using the first encoding method;
A decoding unit for decoding the signal encoded by the first encoding unit;
In the first encoding unit, when the encoding intermediate information generated when encoding is performed according to the first encoding scheme, the first encoding is performed when encoding is performed according to the first encoding scheme. In addition to the encoded video signal encoded by the method, an intermediate information storage memory for storing a plurality of frames,
A compression / decompression unit that compresses the input signal and decompresses the compressed input signal;
An input signal storage memory for storing the input signal compressed by the compression / decompression unit;
Encoding selected from the input signal read from the input signal storage memory and decompressed by the compression / decompression unit and the signal decoded by the decoding unit, and stored in the intermediate information storage memory for the plurality of frames A second encoding unit that encodes the second encoding method using intermediate information;
An encoding device comprising: In claim 1 ,
The encoding apparatus, wherein the intermediate encoding information is a motion vector and / or a quantized value and / or a luminance change statistic and / or a rate transition statistic. In claim 1 ,
The compression and decompression methods include a method for entropy encoding a difference between pixel values from the previous frame, a method for entropy encoding a difference from the left pixel value, a lossless compression method such as LZH or ZIP, JPEG, GIF, An encoding device that is one of the lossy compression methods of PNG. In claim 3 ,
The compression / decompression method is an encoding device that performs switching so that an image with a large number of edge detection points is a compression method of GIF or PNG, and an image with a small number of edge detection points is a JPEG method. In claim 3 ,
The compression / decompression method is an encoding device that performs switching so that an image with a lot of sharp changes in luminance is a GIF or PNG compression method, and a smooth change in luminance is a JPEG method.

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