WO2001067457A1

WO2001067457A1 - High-speed interface for audio player device

Info

Publication number: WO2001067457A1
Application number: PCT/GB2001/000922
Authority: WO
Inventors: George Ian Copland Bruce; Richard Michael Taylor
Original assignee: Digmedia, Inc.; Digmedia Limited
Priority date: 2000-03-07
Filing date: 2001-03-02
Publication date: 2001-09-13
Also published as: AU3584801A; GB0005316D0

Abstract

An audio player device (42) for the playback of compressed data downloaded to the device (42) from a host system. The player device (42) comprises interface means (49) for interfacing with the host system, and solid state memory means (50) for storing the compressed audio data which has been downloaded from the host via the interface (49). The interface means (49) can provide the host system with direct access to the memory system via bus (70). The device (42) also comprises playback means including a decoder (51) for decompressing the compressed audio data.

Description

HIGH-SPEED INTERFACE FOR AUDIO PLAYER DEVICE

The present invention relates to audio player devices for use in playback of compressed audio files, such as MP3 music files . Most specifically, the present invention relates to an interface for enabling high-speed download from a host system to a removable audio player device.

International patent application no. PCT/GB99/03879 (published as no. WO 00/31742) describes an audio player system including a portable base unit for copying digital audio data from an optical storage disk engaged in the base unit, and a complementary audio player device which interfaces with the base unit to enable the copied audio data to be downloaded from the base unit to a solid state memory means in the player device. We refer hereinafter to the base unit as the "MusicStore" and to the removable player device as the "SoulMate". The MusicStore and SoulMate enable a user to compress and copy music from their own collection of compact disks (CDs) and download the compressed files into the memory of the SoulMate. The compressed files are in the well-known MP3 (i.e. MPEG Layer III) compression format. The SoulMate is provided with a decoder for decompressing the downloaded files for playback to the user, e.g. via headphones. Other player devices are currently available which enable a user to playback MP3 files downloaded to the device from the user's personal computer (PC) , for example via a dedicated docking station/unit. The MP3 files may have been purchased by the user, for example via the Internet.

It is a constant aim of designers and manufacturers of such systems and devices to enable the user to achieve fast download of files to the player device. According to the present invention there is provided an audio player device for playback of compressed audio data downloaded to the device from a host system, the player device comprising interface means for interfacing with the host system; solid state memory means for storing compressed audio data downloaded from the host system via the interface; playback means including decoder means for decompressing the compressed audio data for enabling the audio data to be played back to a user; and processor means for controlling operation of the player device, wherein the interface means provide the host system with direct data access to the solid state memory means of the player device .

Conveniently the host system is a base unit such as the above-mentioned MusicStore. Alternatively, the host system may comprise a docking station which is connected between the player device and, for example, a PC from which MP3 files are to be downloaded to the player device. Equally, the host system may be a kiosk from which music files can be purchased, wherein files may be downloaded to the kiosk via a local server, or an Internet download port.

Preferably, the player device interface means supports a high-speed burst write mode that allows very high-speed data transfers directly into the solid state memory means of the device, from the host system. Preferably, data can be transferred to the solid state memory means of the device at a rate of approximately lOMB/s sustained.

Advantageously, the interface means comprises an 8-bit data bus for transfer of data from the host to the device.

Of the 8 lines of the 8-bit data bus, one line may also be used to transmit data from the device to the host in a bit serial fashion. The interface means preferably further includes : a ground connection line; a host handshake line for strobing data from the host to the device and for indicating a request for connection from the host to the device; a device handshake line for strobing data from the device to the host; a clock line for data from the host; and a host enable line for controlling the host's access to the data bus .

The clock line of the interface is preferably connected directly to the clock line .of the solid state memory means in order to function as a strobe to transfer data from the host into the memory means .

The solid state memory means comprises one or more

SDRAM or FLASH memory chips capable of - operating at high speed such- as 15MH_Z. The processing means operates at comparatively low speed such as 4MH_Z.

By by-passing the processor means in the player device, high-speed download of compressed audio data files directly to the solid state memory means of the player device, from the host system, is achieved. In conventional player devices for playback of compressed audio files, the compressed audio file is downloaded to the processor means in the device at comparatively low speed and processed thereby prior to the audio data being transmitted for storage in a memory of the device. This is much slower operation than the high-speed download offered by the interface means in the present invention.

An embodiment of the present invention will now be described by a way of example only and with reference to the following figures in which: Fig. 1 is a perspective view of an audio player device according to the invention, and a base unit to which it can be removably connected;

Fig. 2 is a schematic block diagram showing a prior art arrangement of components of the audio player device of Fig. 1.

Fig. 3 is a schematic block diagram showing components of the player device of Fig. 1 according to a preferred embodiment of the present invention.

Fig. 1 shows a portable audio system comprising a base unit 1 which acts as a host, and . a removable player device 2. The audio player device 2 and base unit 1 plug together via complementary physical and electronic interfaces 3, 4 (of mating edge connector type) to facilitate the download of music, in the form of compressed audio files, such as MP3 files, from the base unit to the player.

Fig. 2 shows the prior art arrangement of the components of the player device 2 as disclosed in WO 00/31742. In this arrangement the player device 2 has a conventional compact flash interface 4 and an ATA (Advanced Technology Attachment) host interface 9 which is operative between the compact flash interface 4 and the microprocessor 12 of the player device 2 enabling control signals and commands to be passed from the player device 2 to the base station 1 and vice versa.

Device 2 comprises microprocessor 12, flash memory 17 for storage of an audio index, solid state memory 10 for storage of compressed audio, MPEG Audio Decoder 11, D/A converter 21, microphone 13, LCD display 19 and control buttons 14, 18.

When an audio file is copied from the base unit 1 to the DRAM 10 of the player device 2 it is transferred in the compressed form in which it is stored in the base unit 1 to the microprocessor 12, via the interfaces 4 and 9 where it is processed to separate audio data from header data which enables indexing of the audio data, the audio data then being delivered to the memory 10 via bus 30, and the header data being delivered via bus 34 to the memory 17. The microprocessor 12 is also connected to the decoder 11 by line 35 for the prupose of enabling the decoder 11 to output stored audio.

.. The preferred embodiment of the ..present invention is shown in Fig. 3 and is concerned with a modified audio player device 42, for use with the base unit 1, and which achieves high-speed download of compressed audio data directly to solid state memory 50, conveniently comprising

^•one- or more SDRAM memory chips. ^* *^* The player device 42 includes a decoder 51 which performs .the decompressing of

MP3 files, D/A converter 61 and output connector 62 (for headphones) to allow playback of the music to a user. A microprocessor 52 in the player device 42 controls operation of the device including operation of the decoder 51 via line 75.

The electronic interface 49 of the player device 42 physically connects directly to interface 3 of the base unit 1 via bus 73 without using the conventional interfaces 4, 9 of Fig 2 and enables the base unit 1 to have direct memory access (DMA) via data bus 70 to the SDRAM memory 50, thereby providing the facility to by-pass the microprocessor 52. However the interface 49 can also access the microprocessor 52 via data bus 72 and the microprocessor 52 can access the memory 50 via bus connection 74.

The interface 49 and its associated buses 73, 70, 72 comprises various signal lines, the functions of which are described in the following protocol:

• A GND signal line (not shown) is generic to buses 73, 70, 72 and provides ground connection for the interface 49.

• AD0-AD7 signal lines are generic to buses 73, 70, 72 and bi-directional and form the 8 bit data bus for ■ transfers from the base unit 1 to the device 42.

These .AD0-AD7 lines are inhibited from .being driven by the base unit 1 when the /BUEN signal is high. The ADO line may also be used to transmit data from the device 42 to the base unit 1 in a bit serial fashion.

••• ■ - A BTSB signal line (not- shown)^, is generic to buses 73 ..and 72 only and provides, an o.utput of base unit 1.,

The BTSB signal is pulled high on the device 42 but is driven by the base unit 1 at all times. The BTSB signal line is the base unit 1 handshake line and is used to strobe data from the base unit 1 to the player device 42. It is also used to indicate a request for connection from the base unit 1 to the player device 42.

• A PACK signal line (not shown) is generic to buses 73 and 72 only and provides a base unit input. The player device 42 drives the PACK signal at all times. When the player device 42 is not connected to the base unit 1 the PACK signal line is driven high. This is the player device handshake line and it is also used to strobe data from the player device 42 to the base unit 1 on the ADO line.

• A CLK signal line is generic to buses 73, 70, 72 and functions bi-directionally. This is the clock line for data received from the base unit 1 when performing burst writes and it is connected to the CLK line of the SDRAM memory 50 and is used as the strobe to transfer data. Each clock pulse strobes in a further byte of data to the SDRAM memory 50 at ascending addresses. Data is placed onto the data bus (ADO - AD7) before CLK is asserted. The rising edge of the clock pulse latches this data directly into the SDRAM memory 50. CLK is pulled down to ground by a resistor and may be driven by either the base unit 1 or player device 42. The command protocol is used to arbitrate between base unit 1 or player device 42 mastership. Before relinquishing mastership of CLK the signal must be driven low to ensure a clean transition.

• A /BUEN signal line.. is generic to buses 73 and 72 only and acts as a host input. /BUEN stands for Base Unit Enable. This signal line is present to allow the data bus 72 to be used for activities other than highspeed data transfers to the SDRAM memory 50. The player device 42 drives the /BUEN signal line at all times. When the /BUEN line is pulled low data can be driven from the base unit 1 onto the data bus 72, into the microprocessor 52. When high the base unit 1 must place the ADO - AD7 signals in a high impedance state. (This control is achieved in hardware) . This is done when the player unit 42 is accessing the SDRAM memory 50 directly, to prevent the base unit 1 interfering with this operation.

During the operation of the device 42 the interface receives a data byte on the data bus, which is clocked via the BSTB signal line, and which is directed to the microprocessor 52. This data byte informs the microprocessor 52 of the nature of the data which it precedes, that is it informs the microprocessor 52 whether the next burst of data will be header data or audio data. Upon processing the data byte the microprocessor 52 strobes data back to the base unit 1, acknowledging receipt, and prepares the player device 42 to receive the impending burst of data. If the packet signal indicated the next burst would contain header data, the microprocessor 52 prepares the PACK line, pulls the BUEN line low causing the header data to be transferred along bus 72 to the microprocessor where it is . processed before being transferred along bus 74 to the memory 50. If the data byte has indicated that the next burst will contain audio data, the microprocessor pulls the BUEN signal line high allowing the audio data to be transferred along bus 70 to the memory 50.^* • The microprocessor 52 operates comparatively slowly, typically at 4MH_Z whereas the memory 50 operates comparatively rapidly, typically at 15MH_Z and in consequence the audio data is high-speed downloaded.

It will be understood that the CLK and /BUEN signals enable the support of burst transfers from the base unit 1, and the interface 49 allows data to be transferred to the solid state memory 50 at a rate of lOMB/s sustained.

Various modifications may be made to the embodiment described without departing from the scope of the invention. For example, the player device 42 may alternatively be plugged into a USB docking unit which is interfaced to a host such as a PC, or a kiosk linked to the Internet or another network via which the compressed audio files are supplied. The docking unit performs a physical protocol conversion from USB (Universal Serial Bus) to the interface protocol described above for downloading from the host to the player device 42 via the USB docking unit. The logical level of the interface between the player device 42 and the host, via the USB docking unit, including downloading commands, remains the same as for a PC parallel port interface between the host and the player.

Claims

1. An audio player device, for playback of compressed data downloaded to the device from a host system, the player device comprising: interface means for interfacing with the host system, solid state memory means for storing compressed audio data downloaded from the host system via the interface means, playback means including decoder means for decompressing the compressed audio data, and processor means for controlling the operation of the player device, wherein the interface means provide the host system with direct access to the solid state memory means of the device.

2. An audio player device according to claim 1 wherein the interface means comprises an 8-bit data bus transfer for transferring data from the host to the device.

3. An audio player device according to claim 2 wherein one line of the 8-bit data bus transmits data from the device to the host in a bit serial fashion.

4. An audio player device according to claim 2 wherein the interface means comprises a ground connection line; a host handshake line for strobing data from the host to the device and for indicating a request for connection from the host to the device; a device handshake line for strobing data from the device to the host; a clock line for data from the host; and a host enable line for controlling the host's access to the data bus.

5. An audio player device according to claim 1 wherein the interface means supports a high-speed burst write mode allowing very high speed data transfers directly into the solid state memory means.

6. An audio player device according to claim 5 wherein data is transferred to the solid state memory means at a rate of 10 MB/s sustained.

7. An audio player device according to claim 1 wherein the solid state memory means comprises at least one SDRAM memory chip.

8. An audio player device according to claim 1 wherein the solid state memory means comprises at least one FLASH memory chip.