JP4496935B2 - Audio / video output device and audio / video output method - Google Patents

Description

  The present invention relates to an audio / video output device (Audio / Video Output Device: hereinafter referred to as AV output) that is used by being connected to a PC (Personal Computer) or the like via a USB (Universal Serial Bus) or a PCI (Peripheral Component Interconnect). Device) and audio / video output method (hereinafter referred to as AV output method).

  FIG. 4 is a schematic configuration diagram of an example of a system using an example of a conventional AV output device. In FIG. 4, 1 is a PC, 2 is a USB, 3 is an example of a conventional AV output device, 4 is an MPEG (Moving Picture Experts Group) standard compressed audio video data (hereinafter referred to as compressed AV data) uncompressed A decoder 5 for decoding audio / video data (hereinafter referred to as uncompressed AV data) is a television.

The system shown in FIG. 4 transfers MPEG standard compressed AV data output from the PC 1 to the AV output device 3 via the USB 2, and the AV output device 3 converts the MPEG standard compressed AV data into uncompressed AV data by the decoder 4. The decoding process and the analog conversion process are performed, and the analog video signal and audio signal are given to the television 5.
JP 2003-202961 A JP 2000-90019 A JP 2002-354051 A

  In the system shown in FIG. 4, the decoding process of the MPEG standard compressed AV data output from the PC 1 is performed by the AV output device 3, but the compressed data format handled by the PC 1 is Divx (digital video express) in addition to MPEG. ) And AVI (audio video interleaving). However, no AV output device has a built-in decoder that supports all these compression formats.

  Therefore, in order to support various types of compressed data handled on the PC 1, it is conceivable to configure a system as shown in FIG. 5 instead of the system shown in FIG. In the system shown in FIG. 5, the PC 1 decodes compressed AV data such as MPEG standards into uncompressed AV data, transfers the uncompressed AV data from the PC 1 to the AV output device 6 via the bus 2, and outputs the AV. The device 6 analogizes the uncompressed AV data and gives the television 5 the analog video signal and audio signal.

  In the AV output device 6, 7 is a buffer for storing uncompressed AV data given from the PC 1 via the USB 2, and 8 is a demultiplexer for separating uncompressed AV data output from the buffer 7 into video data and audio data. A multiplexer 9 is a video encoder that encodes video data output from the demultiplexer 8 into an NTSC (National Television System Committee) video signal, and 10 is an analog signal for audio data output from the demultiplexer 8. This is an audio DA (digital to analog) converter.

  According to the system shown in FIG. 5, since the PC 1 performs decoding processing of compressed AV data into non-compressed AV data, it can cope with various types of compressed data handled on the PC 1. However, if a sufficient bandwidth of USB 2 cannot be secured, sufficient uncompressed AV data cannot be supplied to the AV output device 6, but in general, output of uncompressed AV data from the buffer 7 is performed at a constant rate. Therefore, when the uncompressed AV data in the buffer 7 is exhausted, it becomes impossible to supply a video signal and an audio signal to the television 5.

  For this reason, when video data or audio data in the buffer 7 may be exhausted, it is necessary to supplement the video data or audio data. However, when the video data or audio data is supplemented. Correspondingly, the video data and audio data will remain out of sync unless some measure is taken to synchronize the video data and audio data. Resulting in.

  In view of this point, the present invention is not compressed when video data is complemented when the amount of video data stored in a buffer for storing uncompressed AV data transferred from a predetermined device falls below a predetermined amount. It is a first object of the present invention to provide an AV output device and an AV output method capable of performing audio / video synchronization processing (hereinafter referred to as AV synchronization processing) on a predetermined apparatus side that transfers AV data.

  The present invention also provides a method for storing uncompressed AV data when audio data is complemented when the amount of audio data stored in a buffer for storing uncompressed AV data transferred from a predetermined device falls below a predetermined amount. It is a second object of the present invention to provide an AV output device and an AV output method capable of performing AV synchronization processing on a predetermined device side to be transferred.

  In the present invention, the first invention is an invention of an AV output device, and when a buffer for storing uncompressed AV data transferred from a predetermined device and a video data storage amount of the buffer are less than a predetermined amount, Control means for complementing the video data and notifying the predetermined amount of the complement amount is provided.

  In the present invention, the second invention is an invention of an AV output device, and a buffer for storing uncompressed AV data transferred from a predetermined device, and an audio data storage amount of the buffer being less than a predetermined amount, Control means for supplementing audio data and notifying the predetermined device of the supplement amount is provided.

  In the present invention, the third invention is an invention of an AV output method, in which uncompressed AV data transferred from a predetermined device is stored in a buffer, and the video data storage amount of the buffer falls below a predetermined amount, The video data is complemented and control for notifying the complementing amount to the predetermined device is performed.

  In the present invention, the fourth invention is an invention of an AV output method, in which uncompressed AV data transferred from a predetermined device is stored in a buffer, and the audio data storage amount of the buffer falls below a predetermined amount, The audio data is supplemented, and control for notifying the predetermined device of the supplement amount is performed.

  According to the first invention, when the video data storage amount of the buffer for storing the uncompressed AV data transferred from the predetermined device falls below the predetermined amount, the video data is complemented, and the complement amount is uncompressed. Since the notification is sent to the predetermined device that transfers the AV data, the AV synchronization processing can be performed on the predetermined device side.

  According to the second invention, when the amount of audio data stored in the buffer for storing the uncompressed AV data transferred from the predetermined device falls below the predetermined amount, the audio data is complemented, and the amount of complement is uncompressed. Since the notification is sent to the predetermined device that transfers the AV data, the AV synchronization processing can be performed on the predetermined device side.

  According to the third invention, when the video data storage amount of the buffer for storing the uncompressed AV data transferred from the predetermined device falls below the predetermined amount, the video data is complemented, and the complement amount is uncompressed. Since the notification is sent to the predetermined device that transfers the AV data, the AV synchronization processing can be performed on the predetermined device side.

  According to the fourth aspect of the invention, when the amount of audio data stored in the buffer for storing the uncompressed AV data transferred from the predetermined device is less than the predetermined amount, the audio data is complemented, and the complement amount is uncompressed. Since the notification is sent to the predetermined device that transfers the AV data, the AV synchronization processing can be performed on the predetermined device side.

  Hereinafter, an AV output device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3, including an AV output method according to an embodiment of the present invention.

(overall structure)
FIG. 1 is a schematic configuration diagram of an example of a system using an embodiment of an AV output device of the present invention. In FIG. 1, 11 is a PC, 12 is a USB 2.0 standard USB, 13 is an embodiment of an AV output device of the present invention to which uncompressed AV data or an MPEG stream is transferred from the PC 11 via USB 2, and 14 is a book. It is a television to which an NTSC video signal and an analog audio signal are supplied from an AV output device according to an embodiment 13 of the invention.

  In one embodiment 13 of the AV output device of the present invention, 15 is a USB controller that communicates with the PC 11, and Table 1 shows the assignment of functions to end point 0 to end point 3 defined by USB 2.0. Is shown.

  That is, a control transfer function is assigned to the end point 0. In this example, a command (for example, an AV output start command, an AV output stop command, etc.) for controlling the AV output device according to the embodiment 13 of the present invention is defined with the request type = “vendor”, and the necessary timing. And issued from the host PC 11 to the AV output device according to the thirteenth embodiment of the present invention.

  The end point 1 is assigned a bulk IN transfer function for notifying the PC 11 of a message from the embodiment 13 of the AV output device of the present invention, and a request is periodically issued from the PC 11.

  The end point 2 is assigned a bulk OUT transfer function for transferring video data from the PC 11 to the AV output device according to the embodiment 13 of the present invention, and when the video data is prepared in the PC 11. A request is issued from the PC 11. Table 2 shows the format of video data transferred by the PC 11.

  The end point 3 is assigned with a bulk OUT transfer function for transferring audio data from the PC 11 to the AV output device according to the embodiment 13 of the present invention, and when the audio data is prepared in the PC 11. A request is issued from the PC 11. Table 3 shows the format of audio data transferred by the PC 11.

  16 is an MPEG decoder LSI to which uncompressed AV data or an MPEG stream is transferred from the USB controller 15, and 17 is used for storing uncompressed AV data given from the MPEG decoder LSI 16, decoding the MPEG stream in the MPEG decoder LSI 16, and the like. SDRAM (Synchronous Random Access Memory).

  Reference numeral 18 denotes a video encoder for encoding digital video data defined by ITU-R BT.656 output from the MPEG decoder LSI 16 into an NTSC video signal. Reference numeral 19 denotes an I2S format audio output from the MPEG decoder LSI 16. An audio DA converter that converts data into analog signals.

(Configuration of MPEG decoder LSI 16)
In the MPEG decoder LSI 16, 20 is a CPU (central processing unit) that performs communication with the USB controller 15 and performs overall control within the MPEG decoder LSI 16, 21 is a CPU bus, 22 is uncompressed AV data provided from the USB controller 15. It is a demultiplexer that separates video data and audio data.

  Reference numeral 23 denotes a video writing processing unit (video input processing unit) for performing writing processing (input processing) of uncompressed video data output from the demultiplexer 22 to the SDRAM 17, and reference numeral 24 denotes uncompressed audio data output from the demultiplexer 22. This is an audio writing processing unit (audio input processing unit) that performs processing for writing data to the SDRAM 17 (input processing).

  Reference numeral 25 denotes an SDRAM interface provided for the SDRAM 17, and reference numeral 26 denotes a video output for outputting video data output from the SDRAM 17 to the video encoder 18 as digital video data defined by ITU-R BT.656. A processing unit 27 is an audio output processing unit that outputs the audio data output from the SDRAM 17 to the audio DA converter 19 as I2S format digital audio data.

(Configuration of SDRAM 17)
In the SDRAM 17, 28 is a video writing area that forms a video buffer in which video data is written by the writing process of the video writing processing unit 23, and 29 is an audio buffer in which audio data is written by the writing process of the audio writing processing unit 24. An audio writing area 30 is a memory area used for MPEG stream decoding processing and the like.

  Table 4 shows the sizes of the video writing area 28 and the audio writing area 29. In this example, the video writing area 28 and the audio writing area 29 have input buffers for storing uncompressed AV data transferred from the PC 11. It is configured.

(Flow of uncompressed AV data)
The flow of uncompressed AV data in the system shown in FIG. 1 will be described as follows. Under the control of the device driver in the PC 11, uncompressed AV data is transferred from the PC 11 to the USB controller 15 via the end point 2 and end point 3. In this case, the USB controller 15 time-divides parallel video data and audio data, and transfers uncompressed AV data to the demultiplexer 22 of the MPEG decoder LSI 16.

  If the CPU 20 has not made a write request to the video write processing unit 23 and the audio write processing unit 24, the USB controller 15 does not accept the uncompressed AV data from the PC 11, and does not accept the bulk OUT request from the PC 11. In response, a NAK (Negative Acknowledgment) signal indicating that is returned.

  When the uncompressed AV data is transferred from the USB controller 15, the demultiplexer 22 separates the uncompressed AV data into video data and audio data, transfers the video data to the video writing processing unit 23, The audio data is transferred to the audio writing processing unit 24.

  When the MPEG stream is supplied from the PC 11 to the USB controller 15, the USB controller 15 outputs the MPEG stream to a data bus (not shown) and supplies the MPEG stream to the demultiplexer 22. Are transferred to an MPEG decoding processing unit (not shown).

  The video write processing unit 23 writes the video data supplied from the demultiplexer 22 to the video write area 28 via the SDRAM interface 25 by DMA (Direct Memory Access) transfer in response to a write request from the CPU 20. In this case, the video writing processing unit 23 raises an interrupt to the CPU 20 every time DMA transfer is completed (every frame). Thereby, the CPU 20 can know the amount of video data written into the video writing area 28.

  The audio write processing unit 24 writes the audio data provided from the demultiplexer 22 to the audio write area 29 via the SDRAM interface 25 by DMA transfer in response to a write request from the CPU 20. In this case, the audio writing processing unit 24 raises an interrupt to the CPU 20 every time DMA transfer is completed (every 1152 samples). As a result, the CPU 20 can know the amount of audio data written to the audio writing area 29.

  The video data written in the video writing area 28 is transferred to the video output processing unit 26 via the SDRAM interface 25 in response to a DMA transfer request from the CPU 20. In this case, the video output processing unit 26 raises an interrupt to the CPU 20 every time DMA transfer of video data is completed (every frame). Thereby, the CPU 20 can know the amount of output video data from the video writing area 28.

  The audio data written in the audio writing area 29 is transferred to the audio output processing unit 27 via the SDRAM interface 25 in response to a DMA transfer request from the CPU 20. In this case, the audio output processing unit 27 raises an interrupt to the CPU 20 every time the DMA transfer of audio data is completed (every 1152 samples). Thereby, the CPU 20 can know the amount of output audio data from the audio writing area 29.

  The video data transferred from the video writing area 28 to the video output processing unit 26 is output to the outside of the MPEG decoder LSI 16 as digital video data defined by ITU-R BT.656. The audio data transferred from the audio writing area 29 to the audio output processing unit 27 is output to the outside of the MPEG decoder LSI 16 as I2S format digital audio data.

  Video data output from the video output processing unit 26 is converted into an NTSC video signal by the video encoder 18 and transferred to the television 14. The audio data output from the audio output processing unit 27 is converted into an analog signal by the audio DA converter 19 and transferred to the television 14.

(Process of writing video data to the video writing area 28)
The video data transferred from the demultiplexer 22 to the video writing processor 23 is written in the video writing area 28 by DMA transfer from the video writing processor 23 in order from the head address. Return.

  The write address is managed as a write pointer by the CPU 20, and the write pointer is designated as a transfer start destination at the start of DMA transfer from the video write processing unit 23 to the video write area 28. When the CPU 20 detects the DMA transfer completion interrupt from the video write processing unit 23, the CPU advances the write pointer by the transfer data size. If the final address of the video write area 28 is exceeded, the CPU 20 sets the write pointer. Return to the top address of the video writing area 28.

  As specific transfer control, the above write pointer is set in the “transfer destination register” existing in the video writing processing unit 23, 691200 bytes are set in the “transfer size register”, and the “transfer start register” is set. "1" is set to 1, the DMA transfer of video data from the video writing processor 23 to the video writing area 28 is started. Further, when the DMA transfer is completed, an interrupt is raised from the video writing processing unit 23 to the CPU 20, and the write pointer is advanced at that time.

(Audio data writing process to the audio writing area 29)
The audio data transferred from the demultiplexer 22 to the audio writing processing unit 24 is written in the audio writing area 29 by DMA transfer from the audio writing processing unit 24 in order from the head address. Return.

  The write address is managed as a write pointer by the CPU 20, and the write pointer is designated as a transfer start destination when DMA transfer from the audio write processing unit 24 to the audio write area 29 is started. When the CPU 20 detects the DMA transfer completion interrupt from the audio write processing unit 24, the CPU advances the write pointer by the transfer data size. If the final address of the audio write area 29 is exceeded, the CPU 20 sets the write pointer. The head address of the audio writing area 29 is restored.

  As specific transfer control, the above-described write pointer is set in the “transfer destination pointer register” existing in the audio writing processing unit 24, 4608 bytes are set in the “transfer size register”, and the “transfer start register” is set. When “1” is set to 1, DMA transfer of audio data from the audio writing processing unit 24 to the audio writing area 29 is started. When the DMA transfer is completed, an interrupt is raised from the audio write processing unit 24 to the CPU 20, and the write pointer is advanced at that time.

(Process for reading video data from video writing area 28)
The video data written in the video writing area 28 is transferred to the video output processing unit 26 by DMA transfer in order from the head address of the video writing area 28, and returns to the head address when read to the last address.

  The read address is managed as a read pointer by the CPU 20, and the read pointer is designated as a transfer start source when DMA transfer from the video writing area 28 to the video output processing unit 26 is started. When the CPU 20 detects a DMA transfer completion interrupt from the video output processing unit 26, the CPU advances the read pointer by the transfer data size. If the final address of the video writing area 28 is exceeded, the CPU 20 moves the read pointer. Return to the top address of the video writing area 28.

  As specific transfer control, the above-mentioned read pointer is set in the “transfer source pointer register” existing in the video output processing unit 26, 691200 bytes are set in the “transfer size register”, and the “transfer start register” is set. "1" is set to 1, the DMA transfer of video data from the video writing area 28 to the video output processing unit 26 is started. When the DMA transfer is completed, an interrupt is raised from the video output processing unit 26 to the CPU 20, and the read pointer is advanced at that time.

(Reading audio data from the audio writing area 29)
The audio data written in the audio writing area 29 is transferred to the audio output processing unit 27 by DMA transfer in order from the head address of the audio writing area 29, and returns to the head address when read to the last address.

  The read address is managed as a read pointer by the CPU 20, and the read pointer is designated as a transfer start source when starting DMA transfer from the audio write area 29 to the audio output processing unit 27. When the CPU 20 detects the DMA transfer completion interrupt from the audio output processing unit 27, the CPU advances the read pointer by the transfer data size. If the final address of the audio writing area 29 is exceeded, the CPU 20 advances the read pointer. The head address of the audio writing area 29 is restored.

  As specific transfer control, the above read pointer is set in the “transfer source pointer register” existing in the audio output processing unit 27, 4608 bytes are set in the “transfer size register”, and the “transfer start register” is set. When “1” is set to 1, DMA transfer of audio data from the audio writing area 29 to the audio output processing unit 27 is started. When the DMA transfer is completed, an interrupt is raised from the audio output processing unit 27 to the CPU 20, and the read pointer is advanced at that time.

(AV data overwrite)
In this example, the video data in the video writing area 28 where the DMA transfer to the video output processing unit 26 has not been completed is not overwritten. When there is no free space in the video writing area 28 (when the read pointer has caught up with the write pointer), the bulk OUT transfer from the PC 11 is not accepted and a NAK signal is returned to the PC 11.

  Further, overwriting is not performed on the audio data in the audio writing area 29 where the DMA transfer to the audio output processing unit 27 has not been completed. When there is no free space in the audio writing area 29 (when the read pointer catches up with the write pointer), the bulk OUT transfer from the PC 11 is not accepted and a NAK signal is returned to the PC 11.

(Processing Procedure in Embodiment 13 of AV Output Device of the Present Invention)
FIG. 2 is a flowchart showing a processing procedure in an embodiment 13 of the AV output device of the present invention. In an embodiment 13 of the AV output device of the present invention, the USB controller 15 determines whether or not an AV output start command (defined as a USB vendor request) issued by the device driver of the PC 11 has been received ( Step P1), if received, the received AV output start command is transferred to the CPU 20.

  When the CPU 20 receives the AV output start command from the USB controller 15, the CPU 20 issues a write instruction to the video write processing unit 23 and the audio write processing unit 24. When the video data is accumulated in the video writing area 28 for 2 frames or more and the audio data is accumulated in the audio writing area 29 for 3200 samples or more, AV output is started (step P2).

  Here, the CPU 20 determines whether or not the DMA transfer of the audio data from the audio writing area 29 to the audio output processing unit 27 is stopped (audio output DMA is stopped) (step P3). If there is, the DMA transfer of audio data from the audio writing area 29 to the audio output processing unit 27 is started (audio output DMA start) (step P4).

  On the other hand, when the DMA transfer of the audio data from the audio writing area 29 to the audio output processing section 27 is not stopped (NO in step P3), or from the audio writing area 29 to the audio output processing section 27. When the DMA transfer of the audio data is started, the CPU determines whether or not the DMA transfer of the video data from the video writing area 28 to the video output processing unit 26 is stopped (video output DMA is stopped). Judgment is made (step P5), and if it is stopped, DMA transfer of video data from the video writing area 28 to the video output processing unit 26 is started (video output DMA start) (step P6).

  On the other hand, when the DMA transfer of the video data from the video writing area 28 to the video output processing section 26 is stopped (NO in step P5), or from the video writing area 28 to the video output processing section 26. When the DMA transfer of the video data to the CPU 20 is started, the CPU 20 determines whether or not the DMA transfer of the audio data from the audio writing processing unit 24 to the audio writing area 29 is stopped (the audio input DMA is stopped). (Step P7), and if it is stopped, it is determined whether or not there is a free area in the audio writing area 29 (Audio Buffer not Full) (Step P8). If there is audio data from the audio writing processing unit 24 to the audio writing area 29, It starts DMA transfer (audio input DMA start) (step P9).

  On the other hand, when the DMA transfer of the audio data from the audio writing processing unit 24 to the audio writing area 29 is not stopped (NO in step P7), or when there is no free area in the audio writing area 29 ( In the case of NO in step P8), or when DMA transfer of audio data from the audio writing processor 24 to the audio writing area 29 is started, the CPU 20 transfers the data from the video writing processor 23 to the video writing area 28. It is determined whether or not the DMA transfer of video data is stopped (video input DMA is stopped) (step P10). If it is stopped, there is an empty area in the video writing area 28 (Video Buffer not). Full) is determined (Step P11), and the video writing area 28 has an empty area. In some cases, it initiates a DMA transfer of video data from the video write processor 23 to the video writing area 28 (video input DMA start) (step P12).

  On the other hand, when the DMA transfer of the video data from the video writing processing unit 23 to the video writing area 28 is not stopped (NO in Step P10), or when there is no free area in the video writing area 28 ( In the case of NO in Step P11), or when the DMA transfer of video data from the video writing processing unit 23 to the video writing area 28 is started, the CPU 20 indicates that the audio writing area 29 is almost empty (Audio Buffer It is determined whether or not (Almost Empty) (step P13). When the CPU 20 detects that the untransferred audio data to the audio output processing unit 27 in the audio writing area 29 has fallen below 1152 samples, it is determined that the data is almost empty.

  If the CPU 20 determines that the audio writing area 29 is almost empty, the CPU 20 performs audio data complementing processing (audio complementing processing) (step P14). That is, the CPU 20 performs a process of artificially increasing the audio data for 1152 samples. For example, when the next DMA transfer of audio data from the audio writing area 29 to the audio output processing unit 27 is completed, the CPU 20 normally advances the read pointer by 1152 samples, but does not advance only once. To do.

  Next, the CPU 20 notifies the PC 11 of the audio data complementing amount (audio complementing amount notification) (step P15). That is, the CPU 20 notifies the complemented audio data amount (in this example, 1152 samples = 4608 bytes) to the USB controller 15, and the USB controller 15 notifies the PC 11 from the end point 1.

On the other hand, when it is determined that the audio writing area 29 is almost empty (NO in step P13), or when the PC 11 is notified of the audio data complementing amount, the CPU 20 It is determined whether or not 28 is almost empty (Video Buffer Almost Empty) (step P16). When the CPU 20 detects that the untransferred video data to the video output processing unit 26 in the video writing area 28 has fallen below one frame, it is determined that it is almost empty.

  If the CPU 20 determines that the video writing area 28 is almost empty, the CPU 20 performs a video data complementing process (video complementing process) (step P17). That is, the CPU 20 performs a process of artificially increasing the video data for one frame. For example, when the next DMA transfer from the video writing area 28 to the video output processing unit 26 is completed, the CPU 20 prevents the read pointer from being advanced only once, while the read pointer is normally advanced by one frame.

  Next, the CPU 20 notifies the PC 11 of the video data complementing amount (video complementing amount notification) (step P18). In other words, the CPU 20 notifies the complemented video data amount (in this example, 1 frame = 691200 bytes) to the USB controller 15, and the USB controller 15 notifies the PC 11 from the end point 1.

On the other hand, when it is determined that the video writing area 28 is almost empty (NO in step P16), or when the complement amount of the video data is notified to the PC 11, the CPU 20 determines that the USB controller 15 Determines whether an AV output stop command (defined as a USB vendor request) issued by the device driver of the PC 11 has been received (step P19). If not received, the process returns to step P3. When received, the received AV output start command is transferred to the CPU 20.

  When the CPU 20 receives the AV output stop command from the USB controller 15, the CPU 20 stops the output of the video data and the audio data from the video writing area 28 and the audio writing area 29 (step P20), and the processing is step. Return to P1.

(Processing procedure at PC11)
FIG. 3 is a flowchart showing a processing procedure in the PC 11. The device driver in the PC 11 determines whether or not an AV output start command has been received from higher-level software such as an application (step S1). If received, an AV output start command (as a USB vendor request) is received. Defined) is issued to the AV output device according to an embodiment 13 of the present invention (step S2).

  Next, the device driver of the PC 11 transfers the video data designated by the upper software such as an application from the end point 2 by bulk OUT transfer (step S3). The transfer size of the video data is an arbitrary size determined by the device driver of the PC 11. When the transfer is completed, the device driver of the PC 11 recognizes the completion by the notification from the USB controller 15. Note that the device driver of the PC 11 continuously transfers video data when it starts transferring.

  Further, the device driver of the PC 11 transfers the audio data designated by the upper software such as an application from the end point 3 by bulk OUT transfer (step S4). The transfer size of the audio data is an arbitrary size determined by the device driver of the PC 11. When the transfer is completed, the device driver of the PC 11 recognizes the completion by the notification from the USB controller 15. Note that the device driver of the PC 11 continues to transfer the audio data when it starts transferring the audio data.

  Next, it is determined whether or not there is a video data supplement amount notification from Embodiment 13 of the AV output device of the present invention (step S5). From the frames to be transferred by the device driver of the PC 11, pictures having the same number of frames as the notified supplement amount are thinned out, that is, not transferred (step S6).

  On the other hand, from the embodiment 13 of the AV output device of the present invention, when there is no notification of the supplement amount of video data (in the case of NO in step S5), or the frame to be transferred by the device driver of the PC 11 In the case where the number of pictures corresponding to the notified video data supplement amount is thinned out, it is determined from the embodiment 13 of the AV output device of the present invention whether or not there is an audio data supplement amount notification ( In step S7), when there is a notification of the supplement amount of audio data, the supplement amount is integrated (step S8).

  On the other hand, from the embodiment 13 of the AV output device of the present invention, when there is no audio data supplement amount notification (NO in step S7), or when the audio data supplement amount is integrated. Then, it is determined whether or not the integrated value A of the audio data supplement amount has reached the audio data amount for one frame time (step S9). If it has reached, the frame repeat process is performed (step S10). ). That is, the device driver of the PC 11 repeats one of the video frames to be transferred (transfers the same frame twice to the embodiment 13 of the AV output device of the present invention).

  Here, for example, when one frame time is 33 ms and the audio sampling rate is 48 kHz, in this example, 4 bytes per sample (16 bits × 2 channels),

Audio data for one frame time.

  Next, the calculation of [the integrated value A of the audio data supplement amount = the integrated value A of the audio data supplement amount A-1 audio data amount for one frame time] is performed, and the integrated value A of the audio data supplement amount is updated. (Step S11).

  On the other hand, when the integrated value A of the audio data supplement amount does not reach the data amount for one frame time (NO in step S9), or [integrated value A of audio data supplement amount = audio When the calculation of the integrated value of the data complement amount A−the amount of audio data for the frame time] is performed, the device driver in the PC 11 receives an AV output stop command from the upper software such as an application. If not received, the process returns to step S5. If received, an AV output stop command (defined as a USB vendor request) is output to the AV output of the present invention. The device is issued to the embodiment 13 (step S13).

  Next, the transfer of video data by the bulk OUT transfer from the end point 2 being continuously performed is stopped (step S14), and then the bulk OUT transfer from the end point 3 being continuously performed is stopped. Audio data transfer is stopped (step S15), and the process returns to step S1.

(Effect of Embodiment 13 of AV Output Device of the Invention)
As described above, according to the embodiment 13 of the AV output device of the present invention, when the amount of video data stored in the video writing area 28 falls below one frame as a predetermined amount, the CPU 20 Since the data is complemented and the complement amount is notified to the PC 11 via the USB controller 15, the PC 11 thins out one frame supplemented by the AV output device according to the thirteenth embodiment of the present invention. AV synchronization processing can be performed.

  In addition, when the audio data storage amount in the audio writing area 29 falls below 1152 samples as a predetermined amount, the CPU 20 complements the audio data for 1152 samples, and sends the complement amount to the PC 11 via the USB controller 15. Since the notification is made, the PC 11 can perform the AV synchronization processing by accumulating the amount of audio / data complement and when one frame is reached, the repeat processing for one frame is performed.

  As in this example, when AV synchronization processing is not performed on the AV output device 13 side and AV synchronization processing is performed on the PC 11 side, the processing speed of the CPU provided in the PC 11 and the memory capacity are considered. And effective.

  In the embodiment 13 of the AV output device of the present invention, the AV output device used by connecting to the PC 11 via the USB 12 has been described as an example. However, the AV output device of the present invention is connected via the PCI. The present invention can also be applied to an AV output device used by connecting to the PC 11.

  Patent Document 1 describes a technique in which compressed audio data is decoded by a PC, uncompressed audio data is transferred from the PC to the conversion unit, and an audio signal is transferred from the conversion unit to the head unit. Yes. Patent Document 2 describes a technology in which a transfer source recognizes device information of a transfer destination and selects normal transfer or compression or divided transfer. Patent Document 3 describes a technique for changing the transmission rate of empty packets and data packets to increase or decrease the data transfer amount.

  However, in these Patent Documents 1, 2, and 3, when an AV output device to which uncompressed AV data is transferred, such as the AV output device of the present invention, complements video data or audio data, There is no description that suggests an AV output device that can perform AV synchronization processing on the host side to correct the AV synchronization deviation due to the above.

1 is a schematic configuration diagram of an example of a system using an embodiment of an audio / video (AV) output device of the present invention. FIG. 4 is a flowchart showing a data processing procedure in an embodiment of the audio / video (AV) output device of the present invention. It is a flowchart which shows the process sequence in PC provided with the system shown in FIG. FIG. 1 is a schematic configuration diagram of an example of a system using an example of a conventional audio / video (AV) output device. It is a schematic block diagram of an example of the system which uses another example of an audio video (AV) output device.

Explanation of symbols

1 ... PC
2 ... USB
DESCRIPTION OF SYMBOLS 3 ... Example of conventional audio video (AV) output device 4 ... Decoder 5 ... Television 6 ... Other example of audio video (AV) output device 7 ... Buffer 8 ... Demultiplexer 9 ... Video encoder 10 ... Audio DA Converter 11 ... Personal computer (PC)
12 ... USB
DESCRIPTION OF SYMBOLS 13 ... One Embodiment of the audio video (AV) output device of this invention 14 ... Television 15 ... USB controller 16 ... MPEG decoder LSI
17 ... SDRAM
18 ... Video encoder 19 ... Audio DA converter 20 ... CPU
DESCRIPTION OF SYMBOLS 21 ... CPU bus 22 ... Demultiplexer 23 ... Video write process part 24 ... Audio write process part 25 ... SDRAM interface 26 ... Video output process part 27 ... Audio output process part 28 ... Video write area (video buffer)
29 ... Audio writing area (audio buffer)

Claims (4)

A buffer for storing uncompressed audio / video data transferred from a predetermined device;
When the amount of video data stored in the buffer falls below a predetermined amount, the video data is supplemented, and frames having the same number of frames as the supplement amount of the video data are added to the predetermined device from the frames to be transferred. to skipped, audio-video output device characterized by having a <br/> and control means for notifying the complementary amount to the predetermined device. A buffer for storing uncompressed audio / video data transferred from a predetermined device;
When the amount of audio data stored in the buffer is less than a predetermined amount, the audio data is supplemented, and the predetermined device is integrated with the amount of audio data supplemented, and the integrated value is an audio signal for one frame. when it reaches the amount of data, in order to repeat the processing of one of the frames to be now transferred audio characterized in that it comprises a <br/> and control means for notifying the complementary amount to the predetermined device -Video output device. And storing the non-compressed audio video data transferred from the predetermined device in a buffer,
When the amount of video data stored in the buffer falls below a predetermined amount, the video data is supplemented, and frames having the same number of frames as the supplement amount of the video data are added to the predetermined device from the frames to be transferred. A step of notifying the predetermined device of the complementary amount in order to reduce the amount of data ;
An audio / video output method comprising: And storing the non-compressed audio video data transferred from the predetermined device in a buffer,
When the amount of audio data stored in the buffer is less than a predetermined amount, the audio data is supplemented, and the predetermined device is integrated with the amount of audio data supplemented, and the integrated value is an audio signal for one frame. when it reaches the amount of data, in order to repeat the processing of one of the frames coming forward, a step that notifies said complementary amount to the predetermined device
An audio / video output method comprising:

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