JPH09322161A - Decode device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce disturbance at the time of program switching of video data and audio data by judging the switching of a channel based on a detected program number. SOLUTION: The program number uniquely added for each channel is detected out of a transport stream inputted from a DEMUX device 3 as a demultiplexer and when the switching of the channel is judged based on the detected program number, decode processing for demulti-plexing data into video data and audio data at a system decoder 20 is stopped. At the same time, buffers 20a and 20b for video and audio PES construction as work buffers used for that decode processing are cleared and after the preparation on the side of an A/V decoder 30 is completed, decode processing is restarted based on the transport stream of a new program number.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decoding device for decoding audio information or video information compression-coded according to the MPEG standard, for example.

[0002]

2. Description of the Related Art Conventionally, M has been used for reasons such as realization of high-speed transmission.
PEG (Moving Picture Image Coding Experts)
It has been considered that information (information such as video information or audio information) compressed according to an information compression coding standard such as Group) is transmitted, and is decoded by a decoding device for use.

Since there is only one type of audio information or video information program decoded by this decoding device, the decoding device has set the program number of the program to be decoded. That is, in the decoding device, the system decoding unit normally performs the following processing. The program number in the program map table of the transport stream, the PID list of the transport packet in which an individual stream such as video or audio constituting the program is transmitted, and ancillary information are acquired. If the acquired program number and the program number set in the decoding device match, a list of video and audio PIDs forming the program is stored. PID of PID of video or audio transport packet input after PID is stored
If the IDs match, the video or audio data is transmitted to the audio / video decoding unit for decoding. If it does not match, the transport packet is discarded.

On the high-speed transmission line for supplying data to the decoding device, the transport stream can be frequency-multiplexed and the transport stream of several channels can be placed. Then, by switching the channels of this frequency-multiplexed stream, if the audio and video data are sent to the audio / video decoding section without checking the program number in the system decoding section, the program being decoded Can be switched automatically.

[0005]

However, if the audio / video data is sent to the audio / video decoding section without checking the program number, a data error will occur when the audio / video decoding section decodes the data. Occurrence may cause disturbance of video and sound. This is a format in which one PES packet is constructed by a plurality of transport packets, and one video frame is completed by a plurality of PES packets. Therefore, if the program number is not checked, for example, one This is because the video information is forcibly switched to another program even in the middle of a video frame.

The present invention has been made to solve the above-mentioned problems, and when a stream to be composited is selected from a multiplexed stream and input to a decoding apparatus, the switching timing of the switching timing is decoded. The purpose is to reduce the disturbance when switching programs between video data and audio data.

[0007]

Means for Solving the Problems and Effect of the Invention The decoding device of the present invention made to achieve this object is a digital signal multiplexing stream in which at least one of compression-encoded video or audio information is contained. Is connected to a demultiplexing device that inputs a multiplexed stream corresponding to a plurality of channels, demultiplexes into a specified 1-channel transport stream, and outputs the demultiplexed stream. In a decoding device having a decoding means for decoding the compressed and encoded data based on the transport stream, the program number uniquely assigned to each channel from the transport stream input from the separation device. Detected and the channel is detected based on the detected program number. If the determination means determines that the channel has been changed, and if the determination means determines that the channel is switched, the decoding processing by the decoding means is stopped and the work buffer used for the decoding processing is cleared. A decoding timing control means for restarting the decoding processing by the decoding means based on the transport stream of the new program number.

According to the present decoding device, the judging means determines from the transport stream input from the separating device that
The program number uniquely assigned to each channel can be detected, and it can be determined that the channel has been switched based on the detected program number. If the determination unit determines the channel switching, the decoding timing control Means performs the following control, that is, the decoding processing by the decoding means is stopped, the work buffer used for the decoding processing is cleared, and then the decoding means based on the transport stream of the new program number is used. The decoding process is restarted.

The decoding device is premised on being connected to a separation device, in which a stream containing at least one of video and audio information which has been compression-encoded is digital, for example, time division synchronous multiplexing. A multiplexed stream multiplexed corresponding to a plurality of channels by signal multiplexing is input, and a transport stream of a designated one channel is separated from the multiplexed stream and output to a decoding device.

Therefore, as described above as a problem to be solved, as to the transport stream input from the separation device, the audio / video data is sent to the audio / video decoding unit without checking the program number (channel). If it ends up, audio /
When the video decoding unit decodes, the program number changes, so a data error occurs due to the video information being forcibly switched to another program in the middle of the video frame, and the video or sound is disturbed. Can occur.

On the other hand, in the case of the present invention, when it is determined that the channel has been switched by detecting the program number, the decoding processing by the decoding means is stopped and used for the decoding processing. Since the decoding process by the decoding means based on the transport stream of the new program number is restarted after clearing the work buffer, the disturbance at the time of program switching (at the time of channel switching) can be reduced.

As described above, it is effective when decoding a stream containing at least one of video and audio information, but a video / audio multiplexed transport stream in which video information and audio information are multiplexed. Is often input from the separation device as. In that case, it can be considered to configure as described in claim 2. That is, the decoding means includes a system decoding means for separating the video / audio multiplexed transport stream into a video stream and an audio stream, and a video decoding means for decoding the video stream separated by the system decoding means. Audio decoding means for decoding the audio stream, the decoding timing control means stops the processing by the decoding means for the system, video and audio when the switching means judges the channel switching, and After clearing the video and audio work buffers used for processing, the system, video and audio decoding means based on the transport stream with the new program number are used. That than is to restart the process.

Such a decoding device can be applied to many types of data communication. For example, as a device in which video and audio are combined, a so-called video-on-system considered in a CATV system or the like is used.
There is a demand (VOD) or karaoke service. In the case of a karaoke service, audio alone can be a karaoke accompaniment, but it is now becoming common sense to display a background image corresponding to the karaoke song, so video and audio can be regarded as a set. .

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an MPEG decoder 1 as an embodiment of a decoding device of the present invention.

The MPEG decoder 1 of the present embodiment is a DEMUX device (demultiplexer: demux) as a separating device.
ltiplexer) 3 and inputs the transport stream output from the DEMUX device 3. D
The EMUX device 3 produces a multiplexed stream in which a stream containing at least one of video and audio information that has been compression-encoded is multiplexed corresponding to a plurality of channels by digital signal multiplexing such as time division synchronous multiplexing. It is input, separated into a transport stream of one channel designated according to a channel switching instruction from the key input device 5, and output to the MPEG decoder 1.

The MPEG decoder 1 is the above-mentioned DEMU.
The transport stream from the X device 3 is received by the external input I / F 10, and the received transport stream is video PES packet and audio PE by the system decoder 20 as a system decoding means.
It is classified into S packets. The system decoder 20 has
A ROM 21 in which a processing program of the system decoder 20 is stored and a work RAM 22 of the system decoder 20 are connected.

The system decoder 20 is a video PE.
The S construction buffer 20a and the audio PES construction buffer 20b are provided.
The video PES packet and audio PES packet constructed in 20b are input to an audio / video decoder (hereinafter abbreviated as A / V decoder) 30 via a video channel and an audio channel. The A / V decoder 30 MPEs the input video PES packet and audio PES packet respectively.
It corresponds to “video decoding means” and “audio decoding means” for G decoding. The A / V decoder 30 includes a work RAM 35 for the A / V decoder 30 and an A / V decoder 30.
C as the control means for controlling the / V decoder 30 and corresponding to the "determination means" and the "decode timing control means".
The PU 40 is connected.

The CPU 40 is connected to a ROM 41 storing a program of the CPU 40 and a work RAM 42 of the CPU 40, and is capable of exchanging information notifications with the system decoder 20. . The digital video data output from the digital video output of the A / V decoder 30 is a video D.
It is input to the A converter 50, converted into an NTSC signal which is a video signal of the television in the video DA converter 50, and is externally output. On the other hand, the A / V decoder 30
Digital audio output from the digital audio output
The audio data is input to the audio D / A converter 55, and is converted into an analog audio signal by the audio D / A converter 55 and output to the outside.

The A / V decoder 30 inputs the respective packets separated into the video PES packet and the audio PES packet by the system decoder 20 from the audio channel and the video channel, respectively. The inside of the A / V decoder 30 is divided into two processing blocks of a pre-processing unit 31 and a post-processing unit 32 as shown in FIG. Then, the preprocessing unit 31 separates the header part and the data part of each of the audio and video packets and inputs them into the header buffer and the channel buffer.

The header buffer and the channel buffer are provided in the work RAM 35 of the A / V decoder 30, and as shown in FIG. 2, a video PES header buffer 36 and an audio PES header buffer 37. , A video channel buffer 38 and an audio channel buffer 39.

On the other hand, the post-processing section 32 of the A / V decoder 30
Converts the data in both the video and audio channel buffers 38 and 39 actually assembled by the preprocessing unit 31 into M
PEG encoding is performed, and digital video data and digital audio data are output from each of the digital video output and the digital audio output.

The hardware configuration of the MPEG decoder 1 has been described above. Next, the MPEG decoder 1 will be the DEMUX.
The transport stream that is input from the device 3 and that is to be decoded will be described. FIG. 3 shows the data structure of the transport stream in a hierarchical manner. The transport stream is a stream multiplexed by fixed-length transport packets of 188 bytes. This transport packet is usually PE
It is shorter than the S packet, and the PES packet is divided into transport packets, which are composed of a 4-byte header part and a 184-byte payload as an execution data part. Depending on the flag of the header part, PCR (Progrr) may be inserted between the header part and the payload.
Although an adaptation field part storing am Clock Reference) information and the like may be inserted, it is not considered here.

First, the header portion of the transport packet includes an 8-bit synchronization byte, a 1-bit error indication, a unit start indication and a transport packet priority, and a 13-bit PID (Packet) for identifying the packet. Identification), 2-bit scramble control, 2-bit adaptation field control, and 4-bit cyclic counter.

The PID in this header is the identification information of the data in the payload, and is the system decoder 20 (see FIG. 1).
) Can determine what data the payload is by looking at the PID. But,
Information for linking payload information based on the PID (for example, video when PID = 133, PID =
(Link information such as audio at 134) cannot be obtained without referring to the program map table. This program map table is also stored in the payload of a transport packet having a predetermined PID. The "predetermined PID" of the program map table is stored in the program association table in the payload of the transport packet when PID = 0, and is associated with each program number in the table. Have been.

Next, program association
The payload when the table is stored will be described. The payload in this case consists of an 8-bit pointer field and a 96-bit (12-byte) program
It consists of an association table and 171 bytes of stuffing bytes.

The program association table stores a table ID of 8 bits, a section length of 12 bits, and program number information of 32 bits. The program number information includes a 16-bit program number and a 3-bit program number. Spare and 13-bit program map P
ID. Thus, the program number and the PID of the corresponding program map can be determined. According to the transport stream standard,
Although several combinations of the program number and the program map PID may be stored, one type of program number is stored in the present embodiment.

Further, the payload when the program map table is stored will be described. In this case, the payload is an 8-bit pointer field, a M byte stuffing byte, and a program map file of a predetermined byte [(184-1-M) byte].
It consists of a table and.

The program map table stores a table ID of 8 bits, a section length of 12 bits, and a plurality of program information of predetermined bits. One program information is an 8-bit stream type,
3 bit spare and 13 bit elementary PID
It is composed of 3 bits of spare and N bits of elementary stream (ES) information.

FIG. 4A is an explanatory diagram showing the correspondence between the values of the above 8-bit table ID and the table contents in this embodiment. In this case, Table I
If D is "0X00", it is a program association table, if table ID is "0X01", it is a condition access table, and if table ID is "0X02", it is a program map table.
It is a table.

FIG. 4B is an explanatory diagram showing the correspondence between the 8-bit value in the program information in the program map table and the contents of the stream type. In the present embodiment, if “0X01”, M
It is a PEG1 video stream, and is an MPEG2 video stream in the case of “0X02”. In addition, "0
In the case of “X03”, it is an MPEG1 audio stream, and in the case of “0X04”, it is an MPEG2 audio stream. In the case of “0X05”, it is a private data stream.

Next, the operation of the MPEG decoder 1 of this embodiment will be described. First, the processing in the system decoder 20 for the transport stream received via the external input I / F 10 will be described with reference to the flowchart in FIG.

In S10, the transport packet is received, and in the subsequent S20, it is determined whether or not the PID in the header of the received transport packet corresponds to the program association table. If so (S20: YES), the procedure will be shifted to S100, and it will be determined whether or not the program number set as the program number information in the program association table (see FIG. 3) is changed.

If the determination in S100 is affirmative, that is, if the program number is changed, the program number in the program number information (see FIG. 3) is determined in S110, and the program map PID in the program number information is determined in S120 in a predetermined manner in the RAM 22. Store in the area.

Then, in step S130, the video PES construction buffer 20a and the audio PES construction buffer 20b (see FIG. 1) in the system decoder 20 are cleared, and then the program number switching notice is sent to the CPU 40 in step S140. After that, the CPU 40 waits for the A / V decoder 30 to be in the standby OK state. If it is transmitted (S150: YES), S1
Return to 0.

Since the program map PID has been stored in S120, the next wait is for a transport packet that matches the stored program map PID (S30). In most cases, the packet next to the transport packet in which the program association table was stored becomes the transport packet in which the corresponding program map table was stored.

If the transport packet has the PID of the program map table (S30: YE
S) and S40, and a plurality of program information (see FIG. 3) in the program map table is stored in the RAM.
It is stored in a predetermined area 22. Then, the process returns to S10. Since the program type stores the stream type, the elementary PID, and the like as described above, this allows the video P to be system decoded by itself in the future.
The PID of ES and the PID of audio PES can be obtained.

The system decoder 20 looks at the PIDs of the transport packets received thereafter and determines whether the transport packets are for video (S50).
Is it a transport packet for audio (S6
0) is judged, and if they correspond to each other, the process proceeds to S70, and the video PES packet or audio PE is
The S packet construction process is executed.

Since each of the video PES packet or the audio PES packet is constructed by a plurality of transport packets, it is constructed in the video PES construction buffer 20a or the audio PES construction buffer 20b (see FIG. 1). . S
At 80, it is judged whether or not the construction is completed. If the construction is not completed, the procedure returns to S10 to receive the next transport packet, but if the construction is completed, the video P
A / ES packet or audio PES packet
The process of sending to the V decoder 30 is executed.

As described above, in the system decoder 20,
Link information such as "obtain program number information from program association table-> obtain PID of program map table from program number information-> obtain stream type PID from program information of program map table" After that, the system decoding process described above is performed based on the obtained result.

In the present embodiment, the PID for each stream type corresponding to the program number is uniquely assigned. This is the PI for each stream type
If D is not added uniquely, there will be a time lag before recognizing that the program number has changed, and during that time the stream with the same PID but with a different program number may be A / V decoded. This is to prevent it. For example, in the program map table of program number 1, the video PID is 133, the audio 1 PID is 134, and the audio 2 PID is 135.
On the other hand, in the program map table of program number 2, the video PID is set to 233, the audio 1 PID is set to 234, and the audio 2 PID is set to 235 so that they can be distinguished only by the stream type PID.

The above is the processing by the system decoder 20. Next, the processing when the A / V decoder 30 inputs the video PES and audio PES from the system decoder 20 and performs MPEG decoding will be described. A
When recognizing a video or audio PES packet, the preprocessing unit 31 (see FIG. 2) of the / V decoder 30 converts the PES header into a video PES header buffer 36 or an audio PES header buffer 37 shown in FIG. Write to. Then, the PES header part is stored in the video PES header buffer 36 or the audio PES header.
At the same time as writing to the ES header buffer 37, the CPU
An audio PESReady interrupt is generated for 40. The interrupt processing executed by the CPU 40 will be briefly described. A video or audio channel buffer write pointer and a header buffer write pointer are obtained from the A / V decoder 30, and the video or audio channel buffer write pointer is obtained based on the header buffer write pointer. Alternatively, the audio PES header is read.

If there is a time stamp in the PES header, the time stamp is acquired, and the time stamp and the previously acquired channel buffer write pointer are set in the video or audio time stamp table. As a result, the time stamp table is created. The audio and video time stamp tables are stored in the work RAM of the CPU 40.
It is stored in 42.

On the other hand, separately from the processing of the CPU 40, the post-processing unit 32 of the A / V decoder 30 actually stores the data in the video or audio channel buffers 38 and 39 assembled by the pre-processing unit 31. Is MPEG encoded to output digital video data from the digital video output to the video DA converter 50 or digital audio data from the digital audio output to the audio DA converter 55.

First, referring to the flowchart of FIG. 7, regarding the video, the video channel buffer 38 is checked in the first step S310, and the video data in the buffer 38 exceeds the size of a predetermined one picture. Determine whether or not If you have stored up to the size of one picture (S320: YE
In S) and S330, video decoding is started, and the display on the video black screen (if it is displayed) is canceled. As a result, the decoded video data is output to the video DA converter 50.

First, the audio will be described with reference to the flowchart of FIG. 8. First step S410
In the audio channel buffer 39, the audio data in the buffer 39
Determine if it exceeds the size of the frame.
When the size of one frame is stored (S420:
YES), start audio decoding in S430,
Cancel the audio mute state (if it was, that state). As a result, the decoded audio data is output to the audio DA converter 55.

This is the basic processing relating to A / V decoding. Next, the processing executed by the CPU 40 for program switching, which is a feature of the present invention, will be described with reference to the flowchart of FIG. In the first step S210 of FIG. 6, it is determined whether or not there is a program switch notification from the system decoder 20. this is,
This is notified in S140 of FIG. 5 described above. C
The PU 40 makes the determination in S210 based on this notification.

If there is a program switch notification (S
210: YES), in S220, the A / V decoder 30
A command is issued to stop the decoding process for audio and video, an audio mute command is issued in S230, and a video black screen display command is issued in S240. As a result, when there is a program switching notification, audio data and video data are no longer output from the A / V decoder 30 to the video DA converter 50 and the audio DA converter 55 from that point, and are subsequently input from the system decoder 20. The video PES or audio PES will not be newly decoded.

Then, in the following S250, both the video and audio channel buffers 38 and 3 in the RAM 35.
After clearing 9 (see FIG. 2), in S260, A / V
The system decoder 20 is notified that the decoder 30 is in the standby OK state. With this notification, an affirmative determination is made in S150 of FIG.

As described above, according to the MPEG decoder 1 of this embodiment, the program number uniquely assigned to each channel is detected from the transport stream input from the DEMUX device 3, and the detected program number is set to the detected program number. Based on this, it can be determined that the channel has been switched. Then, as described with reference to FIG. 5, channel switching (change of program number)
If it is determined (S100: YES), the system decoder 20 stops the decoding process for separating video and audio, and the video and audio P that are the work buffers used for the decoding process.
Clear ES construction buffers 20a and 20b, and A / V
After the preparation on the decoder 30 side is completed, the decoding process based on the transport stream having the new program number is restarted.

Further, as described with reference to FIG. 6, when there is a program switch notification from the system decoder 20, the CPU
40 causes the A / V decoder 30 to stop the decoding processing relating to audio and video, mutes the audio, and causes the video black screen to display. As a result, when there is a program switch notification,
At that time, audio data and video data are not output from the A / V decoder 30, and the video PES or audio PES input from the system decoder 20 thereafter is not newly decoded.

After clearing both the video and audio channel buffers 38 and 39 (see FIG. 2) in the RAM 35, the A / V decoder 30 is ready for standby.
Since the system decoder 20 is notified of the state, the PES packet corresponding to the new program number can be sequentially decoded.

As a result, if the transport stream input from the DEMUX device is sent to the A / V decoder 30 without checking the program number (channel), the audio and video data will be decoded. Since the program number changes, forcibly switching to the video information by another program in the middle of the video frame may cause a data error, which may cause distortion of the image or sound. This can be prevented in the MPEG decoder 1 of the form. That is, in the case of the present embodiment, when the channel is switched, the decoding processing in the system decoder 20 and the A / V decoder 30 is stopped, and the work buffer (video PES construction buffer 20a used in the decoding processing is stopped. ， Audio PE
S construction buffer 20b, video channel buffer 3
8. Since the audio channel buffer 39) is cleared and then the decoding process based on the transport stream of the new program number is restarted, the disturbance at the time of program switching (at the time of channel switching) can be reduced.

The present invention is not limited to such an embodiment as described above, and can be carried out in various modes without departing from the scope of the present invention. For example, in the above-described embodiment, a case has been described in which a video stream and an audio stream are input as multiplexed streams, separated from each other in the system decoder 20, and then decoded for each stream. This is similarly effective when decoding at least one stream.

Although such a decoding device can be applied to many types of data communication, for example, if a set of video and audio is a CAT,
What is called video /
There are on demand (VOD) and karaoke services. In the case of a karaoke service, audio alone can be a karaoke accompaniment, but it is now becoming common sense to display a background image corresponding to the karaoke song, so video and audio can be regarded as a set. .

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a decoding device according to an embodiment.

2 is an explanatory diagram showing a configuration of a buffer provided in a work RAM of the A / V decoder of FIG.

FIG. 3 is an explanatory diagram hierarchically showing a data structure of a transport stream.

FIG. 4A is an explanatory diagram showing a correspondence relationship between table ID values and table contents, and FIG.
FIG. 9 is an explanatory diagram showing a correspondence between set values and contents of stream types in program information in a map table.

FIG. 5 is a flowchart showing processing in a system decoder.

FIG. 6 is a flowchart showing processing executed by a CPU regarding program switching.

FIG. 7 is a flowchart showing processing executed by a CPU regarding decoding of video PES.

FIG. 8: CPU for audio PES decoding
5 is a flowchart showing a process executed in.

[Explanation of symbols]

1 ... MPEG decoder 3 ... DEMUX device 5 ... Key input device 10 ... External input I /
F 20 ... System decoder 20a ... Video PES construction buffer 20b ... Audio PES construction buffer 21 ... ROM 22 ... RAM 30 ... A / V decoder 31 ... Pre-processing unit 32 ... Post-processing unit 35 ... RAM 36 ... Video PES header Buffer 37 ... Audio PES header buffer 38 ... Video channel buffer 39 ... Audio channel buffer 40 ... CPU 41 ... ROM 42 ... R
AM 50 ... Video DA converter 55 ... Audio DA converter

Claims (2)

[Claims] 1. A multiplexed stream in which a stream containing compression-encoded information of at least one of video and audio is multiplexed corresponding to a plurality of channels by digital signal multiplexing is input, and is designated from among the multiplexed streams. And a decoding device that is connected to a separation device that separates and outputs a 1-channel transport stream, and that includes decoding means that decodes the compressed and encoded data based on the transport stream input from the separation device. In the device, a determination unit that detects a program number uniquely assigned to each channel from the transport stream input from the separation device and determines that the channel has been switched based on the detected program number, Judgment means determines channel switching In this case, the decoding processing by the decoding means is stopped, the work buffer used for the decoding processing is cleared, and then the decoding processing by the decoding means based on the transport stream of the new program number is restarted. A decoding device comprising: timing control means. 2. A video signal obtained by multiplexing compression-encoded video information and audio information from the separation device.
An audio multiplexed transport stream is input, and the decoding means separates the video / audio multiplexed transport stream into a video stream and an audio stream, and the system decoding means. The decoding apparatus according to claim 1, further comprising: a video decoding unit that decodes the video stream separated by the above, and an audio decoding unit that decodes the audio stream separated by the system decoding unit. When the decision means decides to switch the channel, the processing by each of the system, video, and audio decoding means is stopped, and the video and audio used for the processing are stopped. Clears the work buffer of the I o, the system based on the transport stream new program number, the decoding apparatus characterized by being configured so as to restart the process by the decoding means of video and audio.