JP2003284066A - Decoder and decoding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To output data at a timing intended by a coder, even when a designated outputting time contained in coded data is abnormal. <P>SOLUTION: A separator 14 separates the designated outputting time contained in the coded data, and measures the time of arrival of the coded data. Each PTS judgment portion 15, 17 compares the separated designated outputting time with the measured time of arrival, and judges whether or not the designated outputting time is normal. When the designated outputting time is determined to be abnormal, each PTS correction portion 16, 18 corrects the designated outputting time, and outputs it as reference designated outputting time to a memory control portion 21. The control portion 21 outputs decoded data from a buffer 11 at the reference designated outputting time. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decoding device and a decoding method for decoding coded data and outputting the decoded data.

[0002]

2. Description of the Related Art The international coding standard MPEG2 (Movin
g Picture Experts Group IS
The image and audio compression techniques represented by O / IES1381-2) are becoming widely used in the broadcasting field because of their high image quality and high compression efficiency. The outline of MPEG2 decoding will be described below.

In MPEG2, images and audio are encoded separately. Therefore, in order to synchronize both when decrypting,
Time base reference value PCR (Pro
gram Clock Reference) and PE
S (Packetized Elementary St)
ream) Output designated time PT given in packet units
S (Presentation Time Stam)
The time stamp information of p) is used.

FIG. 4 is a diagram showing an example of the data structure of encoded data (bit stream) according to MPEG2. A pack, which is one unit of encoded data, includes a pack header 1 that stores information about a pack and an image PES (Packetized Elemen) that stores encoded data of an image.
A Tarry Stream packet 2 and an audio PES packet 3 that stores audio encoded data. A time base reference value PCR6 is stored in the pack header 1.

A PES packet is a variable length packetized image coded data (elementary stream) and audio coded data (elementary stream). Image PES packet 2 and audio PES packet 3
Have PES headers 4 and 5, respectively, and output designated times PTS7 and 8 are stored therein. 1 PES
Packets have the same PID (Packet IDenti)
fication: A plurality of TS (Transport Stream) packets 9 each having 13-bit stream identification information and representing the attribute of the individual stream of the packet. The TS packet is a fixed length packet of 188 bytes, and includes a 4-byte TS header 9a and a payload 9b.

The time reference reference value PCR is used as a clock STC (System Time Clock) provided internally in an MPEG2 decoder including a video and audio decoder.
This is information for setting and calibrating the value of k) to a value intended by the encoder side. The time base reference value PCR is transmitted in 42 bits (6 bytes) from the encoder, and P on the decoder side.
At the moment when the final byte forming the CR arrives, the value of the time base reference value PCR is set in the clock STC.

As the output designated time PTS, the clock STC inside the MPEG system decoder measures the time, and when the value of the clock STC matches the PTS, the PES packet is displayed or output (hereinafter simply referred to as output). Is the designated output time. The accuracy of PTS is 33 bits representing a value measured with a clock of 90 kHz. Output designated time P
The TS is given by the encoder for the decoder at the time of encoding.

For example, when the time reference reference value PCR is T0 and the decoder receives the PES packet, t1
To output the decoded image data after 2 seconds, and to output the decoded audio data after t2 seconds from the moment when the decoder receives the PES packet, the image PTS that is the designated output time of the image data is “T0 + t1”, The voice PTS, which is the designated output time of the voice data, is set to "T0 + t2".
In reality, the encoder considers the encoding processing time and the decoding processing time inside the encoder and the decoder, and considers the image PTS “T
0 + t1 ”and voice PTS“ T0 + t2 ”are added.

FIG. 5 is a block diagram showing the basic concept of a conventional image / sound synchronization system using the designated output time PTS. The separation unit 40 of the decoder separates each encoded stream of audio and image from the input stream, and at the same time,
Each audio PTS and image PTS are also separated. The time stamp comparison unit 43 calculates the difference between the PTSs and delays the decoded output of either audio or image according to the result to synchronize the two. At this time, different delays occur in the audio decoder 41 and the image decoder 42, but the audio delay memory 44 and the image delay memory 45, which are delay buffers, may be controlled by including the difference in the delays.

In the MPEG system, the MPEG2 multiplex stream is separated, individual encoded image / audio streams that are elements constituting one program are obtained, and are supplied to the corresponding image / audio decoders. There is a virtual decoder model for expressing the process of performing buffered and synchronized output, and is called a system target decoder (hereinafter STD). STD is designated output time PTS
This is a theoretical model for accurately defining the timing for realizing the synchronous control method using the above, and the actual decoder may have a configuration different from this model (STD).

FIG. 6 is a block diagram showing the structure of a T-STD which is a system target decoder for a transport stream. T-STD is the demultiplexer unit 5
0, transport buffer 51, main buffer 5
2. An image or audio decoder 54. In the case of an image, the main buffer 52 is defined by being divided into two parts, a multiplex buffer 52a and an elementary stream buffer 52b. The multiplex buffer 52a functions so that the data transfer rate to the element re-stream buffer 52b at the next stage can be matched. The elementary stream buffer 52b stores VBV for storing data.
(Video Buffering Verify
r) It has a buffer function.

Although not shown in the figure, a clock STC for measuring the time is provided, and the clock STC has a time reference reference value PCR in the bit stream.
The value of is set.

Next, the operation of T-STD will be described. T-S
The TD defines that an access unit (not shown) of an elementary stream is instantaneously transferred from the main buffer 52 to the decoder 54 and decoded and displayed at a time corresponding to tpn in FIG. That is, this tpn is designated as the output designated time PTS7, 8 by the PES in the encoder.
It is stored in the packet headers 4 and 5. T-STD is
The clock S set by the value of the time base reference value PCR
When the value of TC matches the designated output time PTS, the encoded data in the main buffer 52 is decoded and output.

FIG. 7 is a diagram showing the structure of an MPEG2 bit stream. The size of the main buffer 52 is VBV
It is stored in the sequence header 71 as a buffer size. In addition, the head of each picture of the encoded data (pi
The buffer accumulation information vbv delay indicating the time from the input of the (cture start code) to the VBV buffer until the decoding is stored in the picture header 72, and based on the conditions of the VBV buffer size and the buffer accumulation information vbv delay. The main buffer 52 accumulates an input stream and outputs data by a time stamp.

FIG. 8 is a diagram for explaining the operation of the main buffer 52 in the system target decoder. Each data is stored in the main buffer 52, and each data is output at each output designated time PTS for each buffer storage information vbv delay interval.

As described above, in order to output the image data decoded by the MPEG2 decoder and the decoded audio data at the timing intended by the encoder, the designated output time PTS given by the encoder is normal. Must be a value.

On the other hand, when the MPEG system is used in the broadcasting field, it is required that audio and video AV synchronization be synchronized with each other with an accuracy of several ms. However, if a transmission error occurs due to the state of the encoder or the state of the transmission line between the encoder and the decoder and the designated output time PTS is no longer a normal value, the output control is performed using that PTS. In some cases, the output timing of image data or audio data is not the correct timing and the AV synchronization does not satisfy the required accuracy.

For example, when the time reference reference value PCR is T0 and the decoder receives a PES packet from the moment it is t3.
In the case where both the image PTS and the audio PTS are added as “T0 + t3” in the encoder in order to output the image PES packet and the audio PES packet simultaneously after a second,
When only the audio PTS becomes abnormal due to a transmission error due to the state of the transmission path and becomes "T0 + t4", image data and audio data are not output at the same time. If this difference is within the required accuracy of AV synchronization, there is no problem, but if it exceeds the required accuracy, there is a problem with the reliability of the MPEG system.

The image PTS, which is the designated output time of the image data, is larger than the arrival time of the image data measured by the clock STC set by the time reference value PCR, that is, the image PTS is the arrival of the image data. It is necessary that the time is later than the time, but the image PTS is smaller than the coded data arrival time, that is, the image PT.
If S is earlier than the arrival time of the image data, the image data is not output. If the image data is not output continuously, it may be judged as a broadcast accident.

Further, for example, the image PTS is abnormal,
When the value becomes larger than the buffer size in the stream, the control of the main buffer 52 is not performed correctly, and the main buffer 52 overflows. In that case, the output image data becomes abnormal.

Further, some encoders manufactured before the MPEG standard is established do not comply with the T-STD model and the image PTS is not correctly added. The encoded data produced by such an encoder is T
-It is difficult for a STD-compliant decoder to match the timing of image data and audio data.

[0022]

Since the conventional decoding device is configured as described above, when the output designated time PTS stored in the PES packet is not normal, the image data and the audio data are correctly timed. However, there was a problem that it could not be output with or the output of the image data and the audio data was interrupted.

The present invention has been made to solve the above problems. Even when the designated output time PTS stored in the PES packet is not normal, the image data and the audio are reproduced at the timing intended by the encoder. An object is to obtain a decoding device and a decoding method that can output data without interruption.

[0024]

A decoding device according to the present invention compares a designated output time separated by a separator with a measured arrival time to determine whether the designated output time is normal or not. The determination unit, the PTS correction unit that corrects the output designated time and outputs it as the reference output designated time when it is determined that the output designated time is abnormal, stores the data decoded by the decoder in the buffer, and corrects the PTS. And a memory control unit for outputting the decoded data stored in the buffer at the reference output designated time output by the unit.

In the decoding device according to the present invention, the PTS determination unit determines that the output designated time is abnormal when the designated output time is earlier than the arrival time.

In the decoding device according to the present invention, the PTS correction unit adds a predetermined value set in advance to the arrival time and outputs it as the reference output designated time.

In the decoding device according to the present invention, the PTS correction unit adds the buffer storage amount information included in the encoded data to the arrival time and outputs it as the reference output designated time.

In the decoding apparatus according to the present invention, when the arrival interval determination unit determines that the arrival interval of encoded data is normal, the PTS correction unit corrects the output designated time and outputs it as the reference output designated time. Is.

In the decoding device according to the present invention, when the arrival interval determination unit determines that the arrival interval of the encoded data is abnormal, the PTS correction unit corrects the normal arrival interval of the encoded data at the corrected designated output time. Is added and output as the reference output designated time.

The decoding device according to the present invention compares the designated output time of the image data separated by the separator with the measured arrival time to determine whether the designated output time of the image data is normal or not. A PTS determination unit, an image PTS correction unit that corrects the output designated time of the image data and outputs it as the reference output designated time when the output designated time of the image data is determined to be abnormal, and the audio separated by the separator. When the output designated time of data is compared with the measured arrival time, and the audio PTS determination unit determines whether or not the designated output time of audio data is normal, and when the designated output time of audio data is determined to be abnormal In addition, the audio PTS correction unit that corrects the output designated time of the audio data and outputs it as the reference output designated time, and the image data decoded by the image decoder and the audio decoder Storing the voice data in the buffer, the outputted reference output time specified by the image PTS correction unit,
A memory control unit that outputs the decoded image data stored in the buffer, and outputs the decoded audio data stored in the buffer at the reference output designated time output by the audio PTS correction unit. It is a thing.

In the decoding method according to the present invention, the separated designated output time is compared with the measured arrival time to determine whether the designated output time is normal, and the designated output time is determined to be abnormal. In this case, the output designated time is corrected and output as the reference output designated time, and the decoded data is output at the reference output designated time.

In the decoding method according to the present invention, when it is determined that the arrival interval of the encoded data is normal, the output designated time is corrected and output as the reference output designated time, and the arrival interval of the encoded data is abnormal. When it is determined, the normal arrival interval of encoded data is added to the corrected designated output time and the corrected output designated time is output as the reference output designated time.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. Embodiment 1. 1 is a block diagram showing a configuration of an MPEG2 decoder which is a decoding device according to Embodiment 1 of the present invention. In the figure, 10 is a decoding processing circuit that decodes audio data and image data from encoded data, 11 is a buffer that stores audio data and image data, and 12 is a host CP that collectively controls the decoding processing circuit 10 and the buffer 11.
The MPEG2 decoder, which is U, is roughly composed of a decoding processing circuit 10, a buffer 11 and a host CPU 12. A system bus 13 connects the decoding processing circuit 10 and the host CPU 12 and transmits control signals such as addresses, data and interrupt signals.

Further, in the decoding processing circuit 10 of FIG.
Reference numeral 14 denotes a separator that separates a bit stream that is encoded data into an image ES that is an elementary stream of image data and an audio ES that is an elementary stream of audio data, and an image that is an output designated time of the image data. The PTS and the audio PTS which is the designated output time of the audio data are separated. Further, the separator 14 separates and sets the time reference reference value PCR in the bitstream to the clock STC provided therein, and the time reference reference value PCR
Based on, the time measurement is started, and the arrival time of the image PTS and the arrival time of the audio PTS are measured.

Further, in the decoding processing circuit 10 of FIG. 1, 15 is a separated image PTS and a measured image PT.
An image PTS determination unit (PTS determination unit) that determines whether or not the image PTS is normal by comparing the arrival times of S, 16 corrects the image PTS when the image PTS is determined to be abnormal, and outputs a reference output. An image PTS correction unit (PTS correction unit) 17 that outputs a reference PTS that is a designated time compares the arrival times of the separated audio PTS and the measured audio PTS to determine whether the audio PTS is normal. A voice PTS determination unit (PTS determination unit) 18, which is a voice PTS correction unit (PTS correction unit) that corrects the voice PTS and outputs the reference PTS that is the reference output designated time when the voice PTS is determined to be abnormal. is there.

Further, in the decoding processing circuit 10 of FIG. 1, 19 is an image decoder (decoder) that mainly decodes image data from the separated image ES, and 20 is a separated audio E.
A voice decoder (decoder) for decoding voice data from S, 2
Reference numeral 1 is a memory control unit that controls writing / reading to / from the buffer 11. It is also possible to integrate the entire decoding processing circuit 10 in one LSI.

Further, in the buffer 11 of FIG.
1a is an image ES buffer that stores the separated image ES under the control of the memory control unit 21, and 11b is a sound E that stores the separated sound ES under the control of the memory control unit 21.
An S buffer, 11c is an image output buffer that stores the image data decoded by the image decoder 19 until it is output under the control of the memory control unit 21, and 11d is an audio decoder 20.
It is an audio output buffer that accumulates the audio data decoded by the method until it is output under the control of the memory control unit 21.

Next, the operation will be described. Decoding processing circuit 1 via input means (not shown) of MPEG2 decoder
The encoded data (bit stream) input to 0 is
The separator 14 separates the image ES and the sound ES. The separated image ES and audio ES are respectively controlled by the memory control unit 21 to be the image ES buffer 11a and the audio ES.
It is stored in the buffer 11b.

The image ES and the audio ES stored in the image ES buffer 11a and the audio ES buffer 11b are output to the image decoder 19 and the audio decoder 20, respectively, under the control of the memory controller 21. The image decoder 19 and the audio decoder 20 respectively decode the image data and the audio data, and the decoded image data and the decoded audio data are controlled by the memory control unit 21 and the image output buffer 11 c and the audio output buffer 11 c are output. 11d are stored respectively.

The separator 14 separates the image ES and the sound ES, and at the same time, separates the image PTS and the sound PTS and outputs them to the image PTS determination unit 15 and the sound PTS determination unit 17, respectively. Further, the separator 14 separates the time reference reference value PCR from the input coded data, sets the separated time reference reference value PCR in the internal clock STC, and sets the set time reference reference value PCR. The measurement of the time is started based on the
It outputs to the S determination unit 15, measures the arrival time of the voice PTS, and outputs it to the voice PTS determination unit 17.

The image PTS determination unit 15 determines the phase relationship between the image PTS which is the designated output time of the image data and the arrival time of this image PTS, that is, the front-back relation between the image PTS and the arrival time. If the encoded data input according to the MPEG system standard conforms to the T-STD model, the front-back relationship between the (image) PTS and the arrival time (of the image PTS) is represented by the following equation (1), ) PTS is later than the arrival time. Arrival time <PTS (1) As a result of the determination by the image PTS determination unit 15, (image) PT
If the relationship between S and the arrival time (of the image PTS) does not satisfy the expression (1), it is determined that the image PTS is abnormal, and the arrival time of the image PTS is output to the image PTS correction unit 16 to output the image PTS. Give a correction instruction.

FIG. 2 is a diagram showing a method for correcting the designated output time PTS. Upon receiving the correction instruction from the image PTS determination unit 15, the image PTS correction unit 16 corrects the image PTS according to the following equation (2) from the arrival time of the received image PTS, and specifies the reference output, as shown in FIG. Time (standard PT
S) is output to the memory control unit 21. Reference PTS = arrival time + correction value (2)

Here, the correction value in the above equation (2) may be a predetermined value determined in advance, or may be calculated from vbv delay which is the image buffer accumulation amount information. M
Some encoded data from an encoder that does not comply with PEG2 does not have the image PTS added correctly. In such a case, a known predetermined value is used as a correction value in advance.

On the other hand, the voice PTS judging section 1 which has received the arrival times of the separated voice PTS and the measured voice PTS
Similarly to the image PTS determination unit 15, the audio PTS 7
And the context of the arrival time of the voice PTS is determined. MPE
Encoded data input according to the G system standard is T-ST
If it conforms to the D model, (voice) PTS and (voice P
For the arrival time (of TS), the relationship of the above equation (1) is established. As a result of the determination by the voice PTS determination unit 17, (voice) PTS
And the context of the arrival time (of the voice PTS) is (1) above.
If the expression is not satisfied, it is determined that the audio PTS is abnormal, and the arrival time of the audio PTS is output to the audio PTS correction unit 18,
An instruction to correct the audio PTS is given.

The voice PTS correction unit 18, which receives the correction instruction from the voice PTS determination unit 17, corrects the voice PTS according to the above equation (2) from the arrival time of the received voice PTS, and specifies the reference output designated time (reference PTS). To the memory control unit 21. Here, the correction value may be a predetermined value or vb which is the buffer storage amount information of the image.
It may be calculated from v delay.

Some encoded data from an encoder that is not compliant with MPEG2 does not have the audio PTS added correctly. In such a case, a predetermined value known in advance is used as a correction value. . Further, when the image buffer accumulation amount information vbvdelay is used as the correction value, the output timing of the audio data assumed by the encoder may not be correct, but the situation in which the decoded audio data is not output is avoided. It becomes possible to do.

The memory control unit 21 includes the image PTS correction unit 1
The image data accumulated in the image output buffer 11c at the timing of the reference PTS from
Output as a video output via the audio PTS correction unit 18
Audio output buffer 1 at the timing of the reference PTS from
The audio data stored in 1d is output as an audio output via the audio decoder 20.

As described above, according to the first embodiment, even when the designated output time PTS included in the encoded data is abnormal, the decoded image data and the decoded audio data are correctly timed. It is possible to obtain the effect that the output can be output without interruption.

Embodiment 2. FIG. 3 is a block diagram showing the configuration of an MPEG2 decoder that is a decoding device according to the second embodiment of the present invention. In the figure, reference numeral 22 is an arrival interval determination for determining whether or not the arrival interval of encoded data is normal. The other configuration is the same as the configuration shown in FIG. 1 of the first embodiment.

Next, the operation will be described. Since the designated output time PTS is stored for each PES packet, in order to output the decoded image data and audio data at the correct timing, the determination of the image PTS and the audio PTS and the image are performed as in the first embodiment. PTS correction and voice P
The TS correction is performed every arrival of the PES packet, but the present invention is not limited to this in the following cases.

The image PES packet has a video frame interval of 3
Although the image data arrives in 3 ms, if the video frame arrival interval does not reach 33 ms due to the encoder, if the correction is performed according to the above equation (2), the buffer 11 breaks down and the image data output becomes abnormal.

The arrival interval determination unit 22 counts the intervals at which the image PES packets arrive, and determines the correct arrival interval 33 m.
It is determined whether or not it has arrived in s, and the determination result is the image PT.
It is output to the S correction unit 16. When the arrival interval determination unit 22 determines that the arrival interval is normal, the image PTS correction unit 1
In the sixth embodiment, as in the first embodiment, the image control PTS is corrected by using the above formula (2) to set the reference PTS as the memory control unit 2.
Output to 1.

On the other hand, when the arrival interval determination unit 22 determines that the arrival interval of the subsequent image PES packet is abnormal, the image PTS correction unit 16 corrects the arrived image PTS by the above (2). The above criteria P
The image decoding frame period of 33 ms is added to TS and output to the memory control unit 21 as a new reference PTS.

The arrival interval determination unit 22 also counts the time intervals at which the voice PES packets arrive, determines whether they arrive at the correct arrival intervals, and outputs the determination result as the voice PTS.
Output to the correction unit 18. When the arrival interval determination unit 22 determines that the arrival interval is normal, the voice PTS correction unit 18
Is the same as in the first embodiment, the audio PTS is corrected by using the above equation (2) and the memory control unit 21 is used as the reference PTS.
Output to.

On the other hand, when the arrival interval determination unit 22 determines that the arrival interval of the subsequent audio PES packet is abnormal, the audio PTS correction unit 18 corrects the arrived audio PTS by the above (2). The above criteria P
The speech decoding frame period is added to TS to obtain a new reference P
It is output to the memory control unit 21 as a TS.

Other separators 14 and image PTS judging section 1
5. The processes of the audio PTS determination unit 17, the image decoder 19, the audio decoder 20, and the memory control unit 21 are the same as those in the first embodiment.

As described above, according to the second embodiment, the decoded image data and the decoded audio data are output at the correct timing without interruption even if the arrival interval of the coded data is not normal. The effect that it can be obtained is obtained.

In the first and second embodiments described above,
Although an example of the MPEG2 decoder is described as the decoding device, the present invention can be similarly applied to the case of other decoders.

[0059]

As described above, according to the present invention, the PTS determination for determining whether or not the output designated time is normal by comparing the output designated time separated by the separator with the measured arrival time. Section, a PTS correction unit that corrects the output designated time and outputs it as the reference output designated time when it is determined that the output designated time is abnormal, and stores the data decoded by the decoder in the buffer. Even if the output designated time included in the encoded data is abnormal, by including the memory control unit that outputs the decoded data stored in the buffer at the reference output designated time output by The advantage is that the decoded data can be output without interruption at the correct timing.

According to the present invention, when the designated output time is earlier than the arrival time, the PTS determination unit determines that the designated output time is abnormal, so that the decoded data can be output at correct timing without interruption. The effect is that you can do it.

According to the present invention, the PTS correction unit adds a preset predetermined value to the arrival time and outputs it as the reference output designated time, whereby the output designated time included in the encoded data becomes abnormal. Even in such a case, there is an effect that the decoded data can be output at the correct timing without interruption.

According to the present invention, the PTS correction unit adds the buffer storage amount information included in the encoded data to the arrival time and outputs it as the reference output designated time, so that the output designated time included in the encoded data becomes Even if there is an abnormality, the decoded data can be output at the correct timing without interruption.

According to the present invention, when the arrival interval determination unit determines that the arrival interval of encoded data is normal, P
The TS correction unit corrects the output designated time and outputs it as the reference output designated time, so that even if the designated output time included in the encoded data is abnormal, the decoded data is output at the correct timing without interruption. The effect is that it can be done.

According to the present invention, when the arrival interval determination unit determines that the arrival interval of encoded data is abnormal, P
The TS correction unit adds the normal arrival interval of the encoded data to the corrected output designated time and outputs it as the reference output designated time, so that the encoded data is decoded even if the arrival interval is not normal. There is an effect that the output data can be output without interruption at the correct timing.

According to the present invention, the image PTS determination is performed by comparing the output designated time of the image data separated by the separator with the measured arrival time and determining whether the output designated time of the image data is normal or not. Section and the image PT that corrects the output designated time of the image data and outputs it as the reference output designated time when the output designated time of the image data is determined to be abnormal.
An audio PTS that determines whether or not the output specified time of the audio data separated by the S corrector and the output data of the audio data separated by the separator is compared with the measured arrival time.
A determination unit, an audio PTS correction unit that corrects the output specified time of the audio data and outputs it as the reference output specified time when it is determined that the output specified time of the audio data is abnormal, and the decoded image data is decoded. Stored audio data in the buffer, outputs the decoded image data stored in the buffer at the reference output designation time output by the image PTS correction unit, and specifies the reference output output by the audio PTS correction unit. Even if the output specified time included in the encoded data is abnormal, the decoded image data is provided by including the memory control unit that outputs the decoded audio data stored in the buffer at the time. Thus, there is an effect that the decoded audio data can be output without interruption at the correct timing.

According to the present invention, the output designated time included in the encoded data is separated, the arrival time of the encoded data is measured, the separated output designated time is compared with the measured arrival time, and the output designated. If it is judged whether the time is normal or not, and if the specified output time is abnormal, the specified output time is corrected and output as the specified reference output time, and the decoded data is output at the specified reference output time. By doing so, even if the designated output time included in the encoded data is abnormal, the decoded data can be output without interruption at the correct timing.

According to the present invention, when the arrival interval of encoded data is determined to be normal, the output designated time is corrected and output as the reference output designated time, and the arrival interval of encoded data is determined to be abnormal. In this case, by adding the normal arrival interval of the encoded data to the corrected output specified time and outputting it as the reference output specified time, even if the output specified time included in the encoded data is abnormal. Even if the arrival interval of the encoded data is not normal, the decoded data can be output at the correct timing without interruption.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a decoding device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a PTS correction method in the decoding device according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a decoding device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an example of a data structure of encoded data (bitstream) according to MPEG2.

FIG. 5 is a block diagram showing a basic concept of a conventional image / voice synchronization system using PTS.

[Fig. 6] Fig. 6 is a block diagram illustrating a configuration of a system target decoder of a transport stream.

FIG. 7 is a diagram showing the structure of an MPEG2 bitstream.

FIG. 8 is a diagram illustrating an operation of a main buffer in the system target decoder.

[Explanation of symbols]

10 Decoding Processing Circuit, 11 Buffer, 11a Image E
S buffer, 11b audio ES buffer, 11c image output buffer, 11d audio output buffer, 12 host CPU, 13 system bus, 14 separator, 15 image PTS determination unit, 16 image PTS correction unit, 17 audio P
TS determination unit, 18 audio PTS correction unit, 19 image decoder, 20 audio decoder, 21 memory control unit, 22 arrival interval determination unit.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5C059 KK34 MA00 PP04 RB01 RB14                       RC04 RC32 RE02 RE03 TA03                       TA74 TB04 TC16 TC43 TD14                       UA05 UA34

Claims (9)

[Claims] 1. A decoding device for decoding coded data and outputting the decoded data, comprising: a separator for separating an output designated time included in the coded data and measuring the coded data arrival time. The PTS determination unit that determines whether the output designated time is normal by comparing the output designated time separated by the separator with the measured arrival time, and the output designated time is determined by the PTS determination unit. If determined to be abnormal, the PTS correction unit that corrects the output designated time and outputs it as the reference output designated time, the decoder that decodes the encoded data, and the data decoded by the decoder in the buffer. A memory control unit for storing and outputting the decoded data stored in the buffer at the reference output designated time output by the PTS correction unit. Decoding apparatus. 2. The decoding device according to claim 1, wherein the PTS determination unit determines that the designated output time is abnormal when the designated output time is earlier than the arrival time. 3. The decoding device according to claim 1, wherein the PTS correction unit adds a predetermined value set in advance to the arrival time and outputs it as the reference output designated time. 4. The decoding device according to claim 1, wherein the PTS correction unit adds the buffer storage amount information included in the encoded data to the arrival time and outputs it as the reference output designated time. 5. A PTS is provided with an arrival interval determination unit that determines whether or not the arrival interval of encoded data is normal, and when the arrival interval determination unit determines that the arrival interval of encoded data is normal. The decoding device according to claim 1, wherein the correction unit corrects the output designated time and outputs it as the reference output designated time. 6. When the arrival interval determination unit determines that the arrival interval of the encoded data is abnormal, the PTS correction unit adds the normal arrival interval of the encoded data to the corrected specified output time to obtain a reference value. 6. The decoding device according to claim 5, wherein the decoding device outputs the designated output time. 7. A decoding device which decodes encoded data and outputs the decoded image data and audio data, wherein the image data and the audio data included in the encoded data are separated and the encoded data is converted into the encoded data. A separator that separates the specified output time of the included image data and the specified output time of the audio data, and measures the arrival time of the image data and the arrival time of the audio data, and the output of the image data separated by the separator. An image PTS determination unit that determines whether or not the output designated time of the image data is normal by comparing the designated time and the measured arrival time, and the designated output time of the image data is abnormal by the image PTS determination unit. If it is determined that the image PTS correction unit corrects the output designated time of the image data and outputs it as the reference output designated time, it is separated by the separator. The designated output time of the voice data is compared with the measured arrival time to determine whether the designated output time of the voice data is normal, and the voice PTS determination unit determines the voice data. When the output designated time of is determined to be abnormal, an audio PTS correction unit that corrects the output designated time of the audio data and outputs it as the reference output designated time, and an image that decodes the image data separated by the separator. A decoder, an audio decoder for decoding the audio data separated by the separator, the image data decoded by the image decoder and the audio data decoded by the audio decoder are stored in a buffer, and the image At the reference output designated time output by the PTS correction unit, the decoded image data stored in the buffer is output and the audio PTS correction is performed. The outputted reference output time specified by section, the decoding apparatus characterized by comprising a memory controller for outputting the decoded audio data stored in the buffer. 8. A decoding method for decoding coded data and outputting the decoded data, wherein an output designated time included in the coded data is separated,
The arrival time of the encoded data is measured, the separated output designated time is compared with the measured arrival time to determine whether the output designated time is normal, and the output designated time is determined to be abnormal. In this case, the designated output time is corrected and output as the designated reference output time, and the decoded data is output at the designated reference output time. 9. It is determined whether or not the arrival interval of the encoded data is normal, and when the arrival interval of the encoded data is determined to be normal, the output designated time is corrected to be the reference output designated time. When the output interval of the encoded data is determined to be abnormal, the normal arrival interval of the encoded data is added to the corrected specified output time, and the corrected output specified time is output as the reference output specified time. The decoding method according to claim 8.