JP2001309371A - MPEG decoder - Google Patents

Abstract

(57) [Summary] [Object] To suppress the occurrence of a decoding error when sequentially decoding a plurality of multiplexed image data. When sequentially decoding a plurality of multiplexed streams, decoding assignment of streams is switched for each slice layer. Further, switching in units of slice layers is performed based on, for example, the amount of data stored in the input buffer. Further, skipping of a picture is performed based on the amount of data stored in the input buffer. Further, when the frame rates of a plurality of streams are different, the assignment order is determined according to the frame rates of the respective streams. By these operations, normal display can be performed without causing a decoding error.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for decoding a plurality of multiplexed image data, and more particularly to a decoder for image data compressed according to a standard such as MPEG.

[0002]

2. Description of the Related Art MPEG (Moving Picture Image Coding Experts Gr.) Is an international standard for video data compression technology.
oup) is known. When a plurality of image data (hereinafter, referred to as an MPEG stream or simply a stream) standardized by MPEG are transmitted in a time-division multiplexed manner,
It is necessary to decode a plurality of multiplexed MPEG streams by a decoder.

As a method of decoding a plurality of multiplexed MPEG streams, a plurality of decoders are used to decode a plurality of MPEG streams.
There are a method of processing PEG streams in parallel and a method of sequentially processing a plurality of MPEG streams with one decoder. From the viewpoint of reducing the circuit scale, the latter sequential processing method is advantageous.

[0004]

However, when decoding a plurality of multiplexed MPEG streams by the conventional sequential processing method, the conventional MPEG decoding method has the following problems. In the conventional sequential processing method, switching of each MPEG stream to which decoding is assigned is performed in units of a picture layer. Therefore, during the decoding of one stream, it may not be possible to proceed to the decoding of another stream until a picture layer break occurs, and an error may occur in the decoding of another stream.

FIG. 7 is a diagram for explaining a conventional method of decoding a plurality of streams. In FIG. 7, as an example, four streams (streams) 0, 1, 2, and 3 are sequentially decoded. The decoder has a predetermined period (for example, 1/30 seconds)
, One picture of each stream is decoded. For example, in the cycle t1 of FIG.
Picture P0 of stream 1, picture P0 of stream 2, picture P0 of stream 2, and picture P0 of stream 3.
Are sequentially decoded. Therefore, during the decoding of a picture of one stream, the process does not shift to the decoding of the next stream until a picture break in the stream comes. Therefore, if the decoding of the picture of one stream is delayed due to some trouble (such as an input delay to the decoder), the picture of the subsequent stream may not be decoded within a predetermined period.

As shown in FIG. 7, unless the decoding of the picture P1 of the stream 1 is completed in the cycle t2, the pictures P1 of the subsequent streams 2 and 3 cannot be decoded in the cycle t2. In such a case, a decoding error such as a disturbed image displayed on the screen may occur.

In the sequential processing method, while one stream is being decoded, the decoding of another stream is in a standby state, so that an input buffer provided for each stream in the decoder is not read. On the other hand, since writing to the input buffer is always performed,
Depending on the decoding assignment order, the input buffer may overflow. For example, if a delay occurs in the decoding of the picture P1 of the stream 1 in the cycle t2 in FIG. 7, each input buffer corresponding to the streams 2 and 3 that have not been decoded may overflow. Overflow of the input buffer causes decoding errors such as image distortion.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an image data decoder which suppresses the occurrence of a decoding error when sequentially decoding a plurality of multiplexed image data.

[0009]

According to a first aspect of the present invention, there is provided a decoder for sequentially decoding a plurality of MPEG streams each having a plurality of pictures each including a plurality of slices. It is characterized by comprising an assigning unit that switches the decoding assignment of a plurality of MPEG streams in slice units, and a decoding unit that decodes the MPEG stream assigned by the assigning unit.

According to the present invention, it is possible to switch the assignment of decoding to another stream without waiting for the completion of decoding of one picture.

Further, the decoder according to the present invention further includes a storage unit for storing a plurality of input MPEG streams, and the allocating unit determines the number of MPEG streams stored in the storage unit based on the amount of data stored in each of the plurality of MPEG streams. Thus, decoding assignment of a plurality of MPEG streams is switched. By monitoring the amount of accumulated data, a decoding failure such as a decoding delay can be detected.

For example, the allocating unit switches the decoding allocation to the second MPEG stream when the amount of data stored in the storage unit of the first MPEG stream being decoded becomes equal to or less than a predetermined lower limit. Alternatively, during the decoding of the first MPEG stream, if the amount of data stored in the storage unit of the second MPEG stream that is not being decoded becomes greater than or equal to a predetermined upper limit, the allocating unit may perform decoding allocation to the second MPEG stream. Switch.

A decoder according to the present invention for solving the above-mentioned object comprises a plurality of M pictures each having a plurality of pictures.
In an MPEG decoder that sequentially decodes PEG streams, a storage unit that stores a plurality of input MPEG streams, an allocation unit that sequentially switches decoding allocation of the plurality of MPEG streams stored in the storage unit, and an allocation unit. M
A decoding unit for decoding the PEG stream,
The decoding unit can skip at least one picture of the MPEG stream read from the storage unit when the storage data amount of the assigned MPEG stream in the storage unit is equal to or larger than the predetermined upper limit value.

As described above, by reading out the pictures stored in the storage section without decoding, the pictures can be read out at high speed, and the overflow of the storage section can be avoided.

Further, in order to achieve the above object, the present invention provides a decoder for decoding a plurality of MPEG streams by sequential processing.
An assignment unit that switches the decoding assignment of the G stream according to the frame rate of each of the plurality of MPEG decoders; and an MPE assigned by the assignment unit.
A decoding unit for decoding the G stream.

[0016]

Embodiments of the present invention will be described below. However, the technical scope of the present invention is not limited to the present embodiment.

FIG. 1 is a diagram showing the structure of image data (stream) according to the MPEG standard. The stream is
As shown, it has a plurality of hierarchical structures. The image data has a sequence header (SH) and a group of pictures (GOP). Sequence header (SH)
Is a header for designating a screen format, and includes a horizontal size, a vertical size, a pixel aspect ratio, a frame rate, a bit rate, and the like of the screen. The frame rate is the display cycle of the image (such as 1/30 second or 1/60 second),
The bit rate is the transmission speed (bps) of the stream.

A group of pictures (GOP) is
It has multiple pictures. Pictures include I-pictures,
There are three types: P picture and B picture. I picture is
It is an image that can be decoded independently, and a P picture is
The B picture is an image that is decoded with reference to the preceding I or P picture, and the B picture is an image that is decoded with reference to the preceding and succeeding I and P pictures.

Each picture has a plurality of slices.
A slice is a data sequence obtained by dividing one image into an arbitrary length, and has a width of 16 pixels in the vertical direction. A slice is a minimum unit data string having a start code. Therefore, each of the picture, GOP, and sequence header also has a start code.

A slice is composed of a plurality of macroblocks (M
B). The macro block is a data block having a width of 16 pixels in the vertical and horizontal directions, and the macro block is composed of six 8 × 8 blocks (four blocks for luminance signal (Y) and four blocks for color difference signal (Cb). , C
r) one block for each).

When a plurality of such streams are transmitted after being multiplexed and decoded sequentially, the present invention provides:
Stream switching is possible not only in picture units but also in slice units.

If the decoding of one stream is delayed due to a delay of the input stream or the like, switching the decoding of the stream in units of picture as in the conventional method will cause the decoding of the other stream to proceed as described above. Has a negative effect. However, in the present invention, decoding is switched to the next stream in slice units of the stream being decoded based on the stream switching determination criteria described later.

FIG. 2 is a diagram for explaining the principle of the present invention. In FIG. 2A, in a cycle t2, when it is determined that the switching of the decoding assignment of the stream 1 is performed due to the input delay of the stream 1, even if the decoding of the picture P1 of the stream 1 is in progress, the next stream 2
Is switched to the decoding assignment. After the decoding of the picture 1 of the stream 3 is completed, the decoding of the remaining part of the picture P1 of the stream 1 is performed.

In FIG. 2 (b), when the switching of the decoding assignment is determined during the decoding of the K-th slice of the picture P1 of the stream 1, after the decoding of the K-th slice is completed, the decoding assignment is started. Is changed, and the decoding of the picture P1 (including N slices) of the stream 2 and the stream 3 is performed. Then, K + 1 of the picture P1 of the stream 1
Decoding from the slice is resumed. As a result, even if the decoding of the picture P1 of the stream 1 is delayed, the pictures P1 of the subsequent streams 2 and 3 are normally decoded within one cycle. Therefore, it is possible to suppress the influence of the decoding failure of the stream 1 on the streams 2 and 3.

In FIG. 2C, stream 1
If the switching of the stream decoding assignment is determined during the decoding of the K-th slice of the picture P1, the stream to be decoded is switched during the decoding of the K-th slice. This is particularly effective when the input of stream 1 is completely stopped. That is, if the input of stream 1 is completely stopped, decoding may not reach the K-th slice break. In such a case, the stream cannot be switched while waiting for the break of the slice for decoding. Therefore, the stream is forcibly switched without waiting for the break of the slice. In this case, the decoding of the K-th slice is not completed, and an error occurs in the decoding of the picture 1 of the stream 1. However, the other streams are normally decoded as described above.

FIG. 3 is a block diagram of a decoder according to the embodiment of the present invention. In FIG. 3, as in the example of FIG. 2, MPEG capable of multi-decoding four streams
A decoder 10 is shown. The TS decoder 11 separates one stream in which a plurality of streams are time-division multiplexed into each stream. Separated streams 0, 1,
2, 3 are input buffers 12-0, 12-1, respectively.
12-2 and 12-3 (in the drawing, corresponding to each of the streams 0, 1, 2, and 3;
Input buffers 0, 1, 2, 3). The input buffer control unit 16 monitors the amount of data (the amount of unprocessed data) accumulated in each input buffer, and when the amount of data is equal to or greater than a preset upper limit, and is equal to or less than a preset lower limit. It has the function of notifying the user when it becomes. The upper limit value and the lower limit value are determination criteria for stream stream allocation. That is, in the embodiment of the present invention, switching of decoding assignment is determined based on the unprocessed data amount (accumulated data amount) of the input buffer of each stream of the decoder.

The MPEG parsing unit 14 analyzes the input stream and normally analyzes the picture up to the end of a picture, and then notifies the stream allocation management unit 15 of a picture analysis completion notification.

The stream allocation management unit 15 selects one of the four streams with the selector 13. More specifically, the stream allocation management unit 15 usually
When the picture analysis completion notification is received from the MPEG syntax analysis unit 14, the selector 13 is controlled to sequentially switch the stream to be read. Also, the stream allocation management unit 15 switches the stream to be read based on the notification (not less than the upper limit and not more than the lower limit) from the input buffer control unit 16. When the stream is switched based on the notification from the input buffer control unit 16, the stream allocation management unit 15 notifies the MPEG syntax analysis unit 14 of an analysis stop request. Upon receiving the analysis stop request, the MPEG syntax analysis unit 14 suspends the analysis at the break of the slice of the stream being analyzed, or interrupts the analysis during the analysis of the slice, and starts the analysis in the initial state (start code detection). Status)
Return to

FIG. 4 is a diagram for explaining the operation of the decoder according to the embodiment of the present invention. FIG. 4A shows stream 1
This is an operation when the data amount of the picture P1 of the image P1 becomes equal to or smaller than the lower limit value. If the input is delayed during decoding of picture 1 of stream 1, the amount of data stored in input buffer 12-1 corresponding to stream 1 decreases. Although data is read from the input buffer 12-1,
This is because data is not accumulated because data input is delayed. If the amount of accumulated data is small, data up to the picture break is not included, and decoding is likely to be delayed.

In such a case, switching of the stream decoding assignment is performed. Specifically, FIG.
As shown in (2), when the amount of data stored in the input buffer 12-1 becomes equal to or less than the lower limit, the input buffer controller 16
This is notified to the stream allocation management unit 15. The stream allocation management unit 15 notifies the MPEG syntax analysis unit 14 of an analysis stop request. As a result, the MPEG parsing unit 14 sets the picture P1 at the break of the slice being decoded.
Is temporarily suspended, or the decoding is suspended in the middle of the slice being decoded. When confirming the interruption of the decoding, the stream allocation management unit 15
Switch 3 to stream 2. Thus, the MPEG parsing unit 14 starts decoding the picture P1 of the stream 2 selected by the selector 13 and read next. Thus, the picture P1 of the stream 2 is decoded normally, and subsequently, the picture P1 of the stream 3 is decoded normally. During this time, the input buffer 12-1
Stores the remaining part of the picture P1 of the stream 1. Data capacity exceeds the lower limit.

When the stream allocation management unit 15 receives the analysis completion notification of the picture P1 of the stream 3 from the MPEG syntax analysis unit 14, it switches the selector 13 to the stream 1 again. Thereby, the MPEG syntax analysis unit 14
Reads and decodes the rest of the picture P1 of the stream 1 accumulated during the decoding of the picture P1 of the stream 2 and the stream 3.

With such an operation, the decoder 10
Decoding can proceed without waiting for an input delay of stream 1. When the data amount equal to or larger than the lower limit is accumulated in the input buffer 12-1 corresponding to the stream 1, the decoding allocation to the stream 1 is restarted, and the analysis is performed from the beginning of the next slice where the interruption has been performed, so that no error is caused. Decoding can be performed.

FIG. 4B shows a picture P of stream 1.
This is an operation when the data amount of No. 1 is equal to or more than the upper limit value.
While decoding one stream, the amount of data stored in the input buffer corresponding to another stream may exceed the upper limit. For example, when streams having different data amounts are multiplexed and transmitted, the input frequency of a stream having a large data amount is high, and the input frequency of a stream having a small data amount is low. In such a case, while a certain stream (for example, a stream with low input frequency) is being decoded, an input buffer corresponding to another stream (for example, a stream with high input frequency) may overflow.

In such a case as well, switching of stream decoding assignment is performed. Specifically, FIG.
In (b), when the amount of data stored in the input buffer 12-2 exceeds the upper limit during decoding of the picture P1 of the stream 1, the input buffer control unit 16 notifies the stream allocation management unit 15 of that fact. The stream allocation management unit 15 notifies the MPEG syntax analysis unit 14 of an analysis stop request. Thereby, the MPEG syntax analysis unit 14 temporarily suspends the decoding of the picture P1 at the break of the slice being decoded, or suspends the decoding in the middle of the slice being decoded. When confirming the interruption of the decoding, the stream allocation management unit 15 switches the selector 13 to the stream 2. Thus, the MPEG parsing unit 14 starts decoding the picture P1 of the stream 2 selected by the selector 13 and read next. Thus, the picture P1 of the stream 2 is decoded normally.

When the stream allocation management unit 15 receives the analysis completion notification of the picture P1 of the stream 2 from the MPEG syntax analysis unit 14, it switches the selector 13 to the stream 1 again. Thereby, the MPEG syntax analysis unit 14
Reads and decodes the rest of the picture P1 of the stream 1 again.

With such an operation, the decoder 10
Decoding can proceed while avoiding overflow of the input buffer.

FIG. 5 is a diagram for explaining another operation of the decoder according to the embodiment of the present invention. As described above, when decoding a plurality of multiplexed streams, an overflow of an input buffer may occur depending on the decoding order. When an overflow of the input buffer occurs, a decoding error occurs, and image distortion occurs. In particular, when the error occurs in an I picture or a P picture, an error propagates to a plurality of pictures.

In order to avoid such an error, in another operation of the embodiment of the present invention, when an overflow is likely to occur (when the amount of data stored in the input buffer exceeds the upper limit value), the input buffer Skip the pictures stored in the. To skip a picture, specifically, the picture is only read from the input buffer, and the picture (data below the slice layer) is not analyzed. As a result, the speed of reading data from the input buffer increases, so that the amount of stored data can be rapidly reduced. Such skipping of picture unit data is as follows:
Unlike loss of data due to overflow, continuity of input data is maintained and no decoding error occurs.

In particular, by limiting the types of skipped pictures to B-pictures, only the skipped B-pictures cannot be displayed without affecting other pictures, and one picture is skipped. Can only be displayed.

Although this operation is effective for decoding a plurality of multiplexed streams, it is also effective for decoding one unmultiplexed stream. For example, there is a case where an error occurs in the input bit rate and data rapidly flows into the input buffer.

FIG. 5 illustrates skipping of a picture of one stream for the sake of simplicity. In FIG. 5, at the start of the period t1, the amount of data stored in the input buffer does not exceed the upper limit. The decoder 10 reads and decodes the picture P0 in the input buffer in the cycle t1. Subsequently, the cycle t2
At the start, when the input buffer control unit 16 detects that the accumulated data amount is equal to or more than the upper limit value for some reason, the input buffer control unit 16 notifies the MPEG syntax analysis unit 14 to that effect.
The information may be notified to the MPEG syntax analysis unit via the stream allocation management unit 15.

Upon receiving the above notification, the MPEG syntax analyzer 14 skips the picture P1 stored in the input buffer and decodes the next picture P2. As shown, since the picture P1 is not decoded, it is read out in a short time, and then the picture P2 is decoded as usual.

When a plurality of streams are decoded, the skipping operation and the above-described stream switching operation are described as the operation of the decoder when the amount of data stored in the input buffer exceeds the upper limit. However, one of the decoders may be employed,
Both may be adopted. When both are adopted, for example, both are adjusted as follows. That is, in a certain period, when a certain stream is being decoded and an input buffer corresponding to another stream becomes equal to or more than the upper limit value, first, an operation of switching to another stream is performed. Then, a picture to be decoded in that cycle in the other stream is skipped, and the next picture is decoded.

Further, different upper limits may be given as criteria for the skipping operation and the stream switching operation. For example, the upper limit (first upper limit) of the skip operation is set higher than the upper limit (second upper limit) of the stream switching operation. In this case, in a certain period, when an input buffer corresponding to another stream becomes larger than or equal to the second upper limit while decoding a certain stream, first,
The switching operation to the other stream is performed. At this time, if a stream switching operation is performed after a slice break, data is further accumulated until the switching is actually performed. Then, when the data storage amount when the switching is actually performed is equal to or larger than the first upper limit, the skipping operation is performed, and when the data storage amount is smaller than the first upper limit,
No skipping operation is performed, and the picture to be decoded is decoded in that period.

Incidentally, when a plurality of streams having different frame rates are sequentially decoded, the following problem may occur.

FIG. 6 is a diagram for explaining the sequential decoding of a plurality of streams having different frame rates. In FIG. 6, streams 0 and 1 have a frame rate of 30 Hz.
Stream 2 is a stream with a frame rate of 60 Hz. Here, an MPEG decoder capable of decoding four streams with a frame rate of 30 Hz is assumed. 30
Hz stream is one picture per 1/30 second, 60
Hz stream needs to decode two pictures in 1/30 second, so this decoder uses
1 stream and two 30 Hz streams
Can be decoded in 30 seconds. That is, two pictures can be decoded in 1/60 second by simple calculation.

At this time, in FIG. 6A, if the decoding of the picture P0 of the two 30 Hz streams is first assigned to the first 1/60 second period t1 of the 1/30 second, The pictures P0 and P1 of the 60 Hz stream are decoded in the 1/60 second cycle t2. In the 60 Hz stream, it is necessary to decode one picture every 1/60 second. However, since the picture P0 of the 60 Hz stream is not decoded in the first half of the 1/60 second period t1, the screen display is as shown in FIG. As shown in FIG. 6A, the picture P0 is not displayed, and the picture P1 is displayed for 1/30 second. Thereafter, similarly, the pictures P2 and P3 of the 60 Hz stream 2 are decoded in the latter half of the 1/60 second period t4, so that the picture P2 is not displayed and the picture P3
Will be displayed for 1/30 second, and the normal display will not be performed.

Therefore, in the embodiment of the present invention, in order to solve the above-mentioned inconvenience, the frame rates of a plurality of streams are identified in advance, and the decoding assignment order of the streams is switched according to the frame rate of each stream. Specifically, for each cycle of the highest frame rate, control is performed to assign the decoding of the stream of the frame rate with priority.

More specifically, as shown in FIG. 6 (b), the decode allocation management unit 15 of the decoder 10
In the 60-second cycle, first, the stream 2 of 60 Hz is selected, and when decoding of one picture of the stream 2 of 60 Hz is completed, the stream is switched to one of the streams 0 and 1 of 30 Hz. In FIG. 6B, in the 1/60 second period t1, the picture P0 of the 60 Hz stream 2 is decoded first, and then the picture P0 of the 30 Hz stream 0 is decoded. And the next 1/60 second period t2
First, the picture P1 of the 60 Hz stream is decoded, and then the picture P0 of the 30 Hz stream 1 is decoded. As a result, one picture is decoded every 1/60 second for the stream 2 of 60 Hz, and one picture is decoded every 1/30 second for the streams 0 and 1 of 30 Hz, and normal display is possible.

Before starting decoding a plurality of streams, the stream allocation management unit 15 switches the selector 13 so as to read the first sequence header of the data stored in each input buffer. The MPEG syntax analysis unit 14 analyzes the sequence header of each stream, acquires the frame rate of each stream, and notifies the stream allocation management unit 15 of the frame rate. This allows
The stream allocation management unit 15 identifies the frame rate of each stream, and controls the switching order according to the frame rate of each stream. That is, for each cycle of the fastest frame rate, the stream of the fastest frame rate is assigned first, and then the stream of the slower frame rate is assigned to match the cycle of the slower frame rate.

The MPEG decoder of the present invention can be applied to, for example, a digital broadcast receiver compatible with simultaneous decoding of a plurality of programs, multi-angle broadcasting, and the like.

(Supplementary Note 1) In an MPEG decoder for sequentially decoding a plurality of MPEG streams each having a plurality of pictures each including a plurality of slices, an assignment for switching the decoding assignment of the plurality of input MPEG streams in units of the slices. Department and
A decoder for decoding the MPEG stream assigned by the assigning unit.

(Supplementary Note 2) The allocating unit performs the first MP
While decoding the first picture of the EG stream, switch the decoding assignment to the second MPEG stream,
After the decoding of a part or all of the second picture of the second MPEG stream is completed, the first MPEG
2. The MPEG decoder according to claim 1, wherein a decoding assignment is switched to a stream, and an undecoded portion of the first picture is decoded.

(Supplementary Note 3) When the allocating unit determines to switch the decoding allocation based on a predetermined criterion, the allocating unit waits for the completion of decoding of the slice being decoded of the first MPEG stream, 2. The MPEG decoder according to claim 1, wherein the stream is switched to a stream, and when the stream is switched to the first MPEG stream again, decoding starts from a slice next to the slice.

(Supplementary Note 4) When the allocating unit determines to switch the decoding allocation based on a predetermined criterion, the allocating unit switches to the second MPEG stream in the middle of a slice during decoding of the first MPEG stream,
2. The M-decoding device according to claim 1, wherein the decoding unit starts decoding from a slice next to the slice when switching to the first MPEG stream again.
PEG decoder.

(Supplementary Note 5) The plurality of MPEGs to be input
A storage unit for storing each of the streams, wherein the allocating unit stores the plurality of MPEGs stored in the storage unit.
2. The MPEG decoder according to claim 1, wherein decoding assignment of the plurality of MPEG streams is switched based on the amount of data stored in each stream.

(Supplementary Note 6) The allocating unit switches the decoding allocation to the second MPEG stream when the amount of data stored in the storage unit of the first MPEG stream being decoded falls below a predetermined lower limit. 5. The MPEG decoder according to claim 5, wherein:

(Supplementary Note 7) The allocating unit performs the first MP
During decoding of the EG stream, if the amount of data stored in the storage unit of the second MPEG stream that is not being decoded becomes greater than or equal to a predetermined upper limit, the decoding allocation is switched to the second MPEG stream. 5. The MPEG decoder according to 5.

(Supplementary note 8) MPE for sequentially decoding a plurality of MPEG streams each having a plurality of pictures
A storage unit for storing the plurality of input MPEG streams in the G decoder; an allocation unit for sequentially switching the decoding allocation of the plurality of MPEG streams stored in the storage unit; and an MPEG allocated by the allocation unit. A decoding unit that decodes the stream, and when the amount of data stored in the allocated MPEG stream in the storage unit is equal to or more than a predetermined upper limit, the decoding unit determines at least one of the MPEG streams read from the storage unit. MPE characterized in that a picture can be skipped
G decoder.

(Supplementary note 9) The MPEG decoder according to supplementary note 8, wherein the decoding unit determines whether or not to skip the picture based on the type of picture of the MPEG stream read from the storage unit. .

(Supplementary Note 10) In an MPEG decoder that sequentially decodes a plurality of MPEG streams, an assigning unit that switches a decoding assignment of the plurality of MPEG streams in accordance with a frame rate of each of the plurality of MPEG decoders; A decoding unit for decoding the MPEG stream assigned by the unit.

The scope of protection of the present invention is not limited to the above embodiments, but extends to the inventions described in the claims and their equivalents.

[0063]

As described above, according to the present invention, when sequentially decoding a plurality of multiplexed streams, the decoding allocation of the streams is switched in units of slice layers. Further, switching in units of slice layers is performed based on, for example, the amount of data stored in the input buffer. Further, skipping of a picture is performed based on the amount of data stored in the input buffer. Further, when the frame rates of a plurality of streams are different, the assignment order is determined according to the frame rates of the respective streams. By these operations, without causing a decoding error,
Normal display can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of image data (stream) according to the MPEG standard.

FIG. 2 is a diagram illustrating the principle of the present invention.

FIG. 3 is a block diagram of a decoder according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating an operation of the decoder according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating another operation of the decoder according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating sequential decoding of a plurality of streams having different frame rates.

FIG. 7 is a diagram illustrating a conventional method for decoding a plurality of streams.

[Description of Code] 10 Decoder 12 Input Buffer 13 Selector 14 MPEG Parsing Unit 15 Stream Allocation Management Unit 16 Input Buffer Control Unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C059 KK13 KK33 MA00 PP05 PP06 PP07 RB13 RC28 TA80 TB06 TC18 TD02 UA05

Claims (3)

[Claims] An MPEG decoder for sequentially decoding a plurality of MPEG streams each having a plurality of pictures each including a plurality of slices, wherein an assigning unit switches a decoding assignment of the plurality of input MPEG streams in units of the slices. And a decoding unit for decoding the MPEG stream assigned by the assignment unit. 2. A plurality of Ms each having a plurality of pictures.
An MPEG decoder that sequentially decodes PEG streams, a storage unit that stores the plurality of input MPEG streams, an allocation unit that sequentially switches decoding allocation of the plurality of MPEG streams stored in the storage unit, And a decoding unit that decodes the MPEG stream assigned by the unit. If the amount of data stored in the storage unit is greater than or equal to a predetermined upper limit, the decoding unit is read from the storage unit. An MPEG decoder capable of skipping at least one picture of an MPEG stream. 3. An MPEG decoder for sequentially decoding a plurality of MPEG streams, wherein the plurality of MPEG streams are assigned by decoding.
An MPEG decoder comprising: an assigning unit that switches according to a frame rate of each of the plurality of MPEG decoders; and a decoding unit that decodes an MPEG stream assigned by the assigning unit.