MPEG coded picture decoding apparatus

An MPEG coded picture decoding apparatus is provided which can display video data quite the same as original data even if a miss of MPEG coded video data occurs in a transmission line or the like. The MPEG coded picture decoding apparatus includes a stream buffer memory for storing an MPEG stream, a pack header processing section for separating a pack header of the MPEG stream and extracting SCR information, a PES packet processing section for separating a header of a PES stream, extracting PTS information and separating packets, a GOP detection section for detecting a GOP of a video stream, a video buffer memory for storing the video stream, a video MPEG decoding section for MPEG decoding the video stream, a decoded data storage section for storing and managing one picture frame, a video display processing section for storing several picture frames and reading out at a display timing, and an error information processing section for supervising a picture frame memory at each display timing and developing a video re-sending request when the picture frame memory is in an irregular condition.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an MPEG-2 (Moving Picture Experts Group) 
(hereinafter MPEG) coded picture decoding apparatus, and more particularly 
to an MPEG coded picture decoding apparatus which includes an error 
picture re-sending section which is used when MPEG coded picture data 
suffer from a data error such as a miss of data in a transmission line or 
the like. 
2. Description of the Related Art 
In a conventional MPEG coded picture decoding apparatus, when an 
uncorrectable code error, for example, a transmission error such as a long 
burst error, occurs with MPEG coded picture data in a transmission line, a 
decoded picture suffers from significant degradation in picture quality or 
a missing portion is produced in a picture. Therefore, the degraded 
picture or the picture having the missing part is replaced with another 
picture in the past on the decoding side to correct the picture smoothly 
with respect to a surrounding picture. 
For example, in a moving picture decoding apparatus disclosed in Japanese 
Patent Laid-Open Application No. Heisei 5-153574, a block in which an 
uncorrectable code error has occurred is replaced with a block picture 
produced based on motion vectors in the past determined based on frame 
pictures in the past and then is decoded thereby to correct a missing 
portion of the picture, which arises from the code error, smoothly with 
respect to a surrounding picture irrespective of whether or not the 
decoded picture exhibits some motion. 
In the conventional MPEG coded picture decoding apparatus described above, 
since a degraded or missing portion of a decoded picture caused by a 
transmission error is merely replaced with a block picture produced based 
on motion vectors in the past, blurring of the contour of the corrected 
image cannot be avoided, and it is impossible to decode and display the 
same picture as a picture which does not suffer from the degradation or 
miss. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an MPEG coded picture 
decoding apparatus which can decode and display, even if a miss of MPEG 
coded video data occurs, for example, on the MPEG coding multiplexing 
side, in a transmission line or the like, video data the same as original 
data, which do not suffer from the miss, in units of one picture frame or 
one GOP (Group of Pictures) and can display pictures for several picture 
frames successively without suffering from a miss of a picture caused by 
the miss of the data. 
In order to attain the object described above, according to the present 
invention, there is provided an MPEG coded picture decoding apparatus for 
MPEG coded au picture data transmitted thereto from an MPEG coding 
multiplexing side by means of a decoding element, comprising a memory for 
temporarily storing video data MPEG decoded by the decoding element in 
units of one picture frame, a memory management section for supervising 
the memory to detect whether or not picture data for one frame are stored 
into the memory completely without a miss, a video display processing 
section including a display memory into which video data for one picture 
frame successively read out from the memory are temporarily stored for 
several picture frames and from which the video data are read out so as to 
be displayed in the same order in units of one picture frame, an error 
processing section for checking memory storage information at an output of 
the memory management section at each video display timing and for 
outputting, when the memory storage information is not outputted from the 
memory management section, error information determining that a miss of 
data has occurred with a picture frame stored immediately before the 
display timing then and delivering a re-sending request to the MPEG 
coding-multiplexing side to re-send video data for the one picture frame, 
with which the miss of data has occurred, before the video data of the 
picture frame, with which the miss of data has occurred, or a GOP 
including the picture frame are read out from the video display processing 
section, and a control section for storing video data of the one picture 
frame or the GOP re-sent from the MPEG coding multiplexing side into the 
display memory of the video display processing section by a time at which 
the video data are to be displayed. 
In the MPEG coded picture decoding apparatus, MPEG coded picture data are 
temporarily stored into the memory in units of one picture frame, and it 
is detected by supervision by the memory management section whether or not 
picture data for one frame are stored into the memory completely without a 
miss. Then, video data for one picture frame successively read out from 
the memory are temporarily stored for several picture frames into the 
display memory and then successively read out from the display memory in 
the same order in units of one picture frame so as to be displayed. 
Meanwhile, the storage condition of the memory for one picture frame is 
checked at each video display timing, and when picture data for one 
picture frame are not stored completely, it is determined that a miss of 
data has occurred with a picture frame stored immediately before the 
display timing then. Then, a re-sending request is delivered to the MPEG 
coding multiplexing side to re-send video data for the one picture frame, 
with which the miss of data has occurred, before the video data of the 
picture frame, with which the miss of data has occurred, or a GOP 
including the picture frame are read out from the video display processing 
section. Then, video data re-sent from the MPEG coding multiplexing side 
are stored newly into the display memory by a time at which the video data 
are to be displayed. Consequently, even if a miss of MPEG coded data 
occurs in the MPEG coding multiplexing side, the transmission line or the 
like, video data same as the original data which do not suffer from any 
miss can be displayed in units of a one picture frame or in units of a 
GOP. Accordingly, successive picture frames including the picture frame 
with which the miss of data has occurred can be displayed successively 
without a miss of any picture. 
Further, since the error information can be used as a requesting signal to 
stop sending out of video data from the MPEG coding side following the 
picture frame with which the miss of data has occurred, even if the MPEG 
coded data after the miss of data are influenced by noise of the 
transmission line or by some other cause and suffer from an error, the 
display video data of a wrong picture frame or frames are not outputted. 
Consequently, a disagreeable feeling which may arise from such wrong 
picture frame or frames is not given to the video viewer at all. 
According to another aspect of the present invention to provide an MPEG 
coded picture decoding apparatus, comprising a first memory for 
successively and temporarily storing a multiplexed stream inputted thereto 
from an MPEG coding multiplexing side via a transmission line and a line 
input interface and multiplexed from MPEG coded bit streams of a plurality 
of media including video and audio data, a pack header processing section 
for separating a pack header of the multiplexed stream read out from the 
first memory in response to a first control signal and extracting system 
clock reference information for a system clock reference, a packet 
processing section for separating a packet header from the multiplexed 
stream from the packet header separation section from which the pack 
header has been separated, extracting presentation time stamp information 
for a time reference and separating the multiplexed stream from the pack 
header processing section in units of a packet of each of the plurality of 
media, a GOP detection section for detecting a GOP from an MPEG video 
stream of video packets separated by the packet processing section, a 
first control section for outputting the first control signal and a second 
control signal in response to a GOP detection signal from the GOP 
detection section, a second memory for temporarily storing the MPEG video 
stream of the video packets separated by the packet processing section and 
being controlled by the second control signal from the first control 
section to read out the MPEG video stream temporarily stored therein in 
units of a GOP, a video MPEG decoding section for being controlled by a 
third control signal to MPEG decode video data in units of one picture 
frame outputted from the second memory, a third memory for temporarily 
storing decoded video data for one picture frame from the video MPEG 
decoding section, a memory management section for supervising a storage 
condition of the decoded video data for one picture frame into a storage 
region of the third memory and controlling, when the storage condition is 
regular, the third memory to output the decoded video data for one picture 
frame stored in the third memory, but outputting, when the storage 
condition is irregular, first error information, a fourth memory for 
temporarily storing the decoded video data for one picture frame outputted 
from the third memory for a first number of picture frames, a video 
display control section for controlling the decoded video data read out in 
units of one picture frame from the fourth memory in response to a fourth 
control signal so that the decoded video data may be outputted at a video 
display timing, a digital to analog conversion section for performing 
digital to analog conversion of the coded video data for each one picture 
frame from the video display control section and outputting and supplying 
the resulting analog decoded video data as an MPEG decoded picture signal 
to an external video viewer, a second control section for outputting the 
third and fourth control signals in response to a fifth control signal so 
that the third control signal is supplied to the second memory and the 
fourth control signal is supplied to the fourth memory, a display timing 
production section for producing and supplying the video display timing to 
the video display control section in order to allow the MPEG decoded 
picture signal outputted from the digital to analog conversion section to 
be displayed at a timing on a picture monitor of the video viewer, an 
error information processing section for supervising an input thereto of 
the first error information outputted from the memory management section 
at a timing of a period equal to that of the video display timing 
outputted from the display timing production section and outputting, when 
the first error information is inputted thereto, a video re-sending 
request signal based on the error information to the MPEG coding 
multiplexing side to request for re-sending of video data of the same 
picture frame as that of the video data with regard to which the first 
error information is outputted, a clock generation section for generating 
a decoding side clock signal to be used for MPEG decoding based on the 
system clock reference information extracted by the pack header processing 
section, a time information production section for producing decoding side 
time information to be used for MPEG decoding based on the presentation 
time stamp information extracted by the packet processing section, a 
synchronization timing production section for producing an AV 
synchronization timing for synchronization between the video and audio 
data upon MPEG decoding based on the decoding side time information 
outputted from the time information production section, and a CPU control 
section for receiving the decoding side clock signal from the clock 
generation section, the decoding side time information from the time 
information production section, the GOP detection signal from the GOP 
detection section and the video re-sending request signal from the error 
information processing section to drive a host CPU to control the MPEG 
decoding processing of the MPEG decoding section via a CPU bus and to 
output the fifth control signal to control the second control section and 
sending out the video re-sending request signal to the MPEG coding 
multiplexing side via a line output interface and the transmission line. 
The above and other objects, features and advantages of the present 
invention will become apparent from the following description and the 
appended claims, taken in conjunction with the accompanying drawings in 
which like parts or elements are denoted by like reference characters.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIG. 1, there is shown an MPEG coded picture decoding 
apparatus to which the present invention is applied. The MPEG coded 
picture decoding apparatus shown includes a stream buffer memory 1, a 
buffer memory control section 2, a pack header processing section 3, a PES 
packet processing section 4, a GOP detection section 5, a video buffer 
memory 6, a buffer memory control section 7, a video MPEG decoding section 
8, a decoded data storage section 9, a video display processing section 
10, a display timing production section 11, a video D/A conversion section 
12, a frame check detection section 13, an error information processing 
section 14, a clock generation section 15, a time information production 
section 16, an audio buffer memory 19, an AV synchronization timing 
production section 20, an audio MPEG decoding section 21, an audio D/A 
conversion section 22, and a CPU control section 25. 
The stream buffer memory 1 temporarily stores a bit stream of MPEG coded 
multiplexed data sent out from a server side, that is, an MPEG coding 
multiplexing side via a high speed digital data private line, which flows 
digital data at a high speed in a fixed rate, and inputted thereto from a 
line interface section 26. The MPEG coded multiplex data are composed of 
multiplexed bit streams of a plurality of media of multimedia on-demand 
information such as moving pictures and sound. 
The pack header processing section 3 includes a header detection and 
separation section 30 which separates a pack header of a bit stream of a 
pack layer read out from the stream buffer memory 1 under the control of 
the buffer memory control section 2 and detects a stream identification 
code (stream ID) of the separated pack header, and an SCR extraction 
section 31 for extracting, based on the stream identification code 
detected by the header detection and separation section 30, SCR code 
information for a system clock reference disposed subsequently to the 
stream identification code. 
The PES packet processing section 4 includes a header separation section 40 
for separating a PES (Packetized Elementary Stream) packet header from a 
stream for each medium factor packetized from a bit stream of an output of 
the pack header processing section 3 from which packet headers have been 
separated, and a PTS extraction section 41 for detecting a stream ID in 
the PES packet header separated by the header separation section 40 and 
extracting PTS (Presentation Time Stamp) code information which is video 
display time information in an optional PES header not shown disposed 
subsequently to the stream ID. The PES packet processing section 4 further 
includes a packet separation section 42 for separating, based on the 
stream ID in the PES packet header, video packets and audio packets from 
each other for each pack from the bit stream, from which PES packet 
headers have been separated, and outputting the video packets and the 
audio packets to a video packet output port, a GOP (Group Of Pictures) 
output port and an audio packet output port. 
The PES packet processing section 4 detects a GOP flag which indicates the 
start of a VOP video stream from video packets for each of separated 
packets inputted thereto from the GOP output port of the PES packet 
processing section 4 from which PES packet headers have been separated. 
The video buffer memory 6 temporarily stores a video stream inputted 
thereto from the video packet output port of the PES packet processing 
section 4. From the video buffer memory 6, picture data in the stored bit 
stream are read out in units of a GOP under the control of the buffer 
memory control section 2 and read out in units of one picture frame under 
the control of the buffer memory control section 7. 
The video MPEG decoding section 8 MPEG decodes video data read out for each 
one picture frame of a unit of a GOP from the video buffer memory 6 under 
the control of a host CPU 18 via a CPU bus 17 and a host memory 23. 
The decoded data storage section 9 includes a picture decoded data frame 
memory 90 for temporarily storing video data for one picture frame decoded 
by the video MPEG decoding section 8, and a memory management section 91 
for supervising the storage condition of video data in a memory region 
temporarily stored in the picture decoded data frame memory 90 and 
stopping, when a data error such as a miss of video data in a 
predetermined memory region is detected, outputting from the picture 
decoded data frame memory 90 of video data of the one picture frame with 
which the data error has occurred and outputting an error detection 
signal, but outputting, if the video data are stored into the 
predetermined memory region without a miss of them, a regular storage 
signal simultaneously upon completion of the storage. 
The video display processing section 10 includes a video display frame 
memory 100 for temporarily storing miss-free regular video data for 
several picture frames successively inputted thereto from the decoded data 
storage section 9, and a display control section 101 for being controlled 
by a video display timing signal outputted from the display timing 
production section 11 to output video data for one picture frame read out 
from the video display frame memory 100 under the control of the buffer 
memory control section 7 so that the video data may be displayed on a 
picture monitor of an external viewer not shown. 
The video D/A conversion section 12 performs digital to analog (D/A) 
conversion of display video data outputted from the video display 
processing section 10 and outputs resulting analog data to the picture 
monitor of the external viewer mentioned above. 
The video display processing section 10 receives, as input signals thereto, 
a regular storage signal outputted from the memory management section 91 
of the decoded data storage section 9 and a video display timing signal 
outputted from the display timing production section 11. Then, the video 
display processing section 10 determines, if a regular storage signal is 
not inputted thereto when a video display timing signal is inputted 
thereto, that video data stored in the picture decoded data frame memory 
90 suffer from a data error such as a miss, and outputs an error detection 
signal together with the error information. 
The error information processing section 14 outputs, when a data error 
detection signal is inputted thereto from the frame check detection 
section 13, based on error information then, a video re-sending request 
signal for requesting for re-sending of video data of a picture frame, 
which which the data error has occurred, from the MPEG coding multiplexing 
side, a video stopping request signal for requesting for stopping of 
sending out of video data from the MPEG coding multiplexing side or a like 
signal. 
The clock generation section 15 produces an intra-apparatus clock signal 
for MPEG decoding processing and so forth based on SCR code information 
extracted by the SCR extraction section 31 of the pack header processing 
section 3. 
The time information production section 16 produces intra-apparatus time 
information for a read timing and an audio/video synchronization (AV 
synchronization) timing of MPEG decoded picture frame data based on PTS 
code information extracted by the PTS extraction section 41 of the PES 
packet processing section 4. 
The display timing production section 11 outputs a display timing for 
picture frame picture display and a checking timing for checking of a 
picture frame memory storage condition and supplies them to the display 
control section 101 of the video display processing section 10 and the 
frame check detection section 13. 
The buffer memory control section 2 controls reading out of pack stream 
data temporarily stored in the stream buffer memory 1 in response to a GOP 
detection signal supplied thereto from the GOP detection section 5 after 
each period of a GOP flag and controls, in response to the same GOP 
detection signal, reading out of 1 video PES stream data temporarily 
stored in the video buffer memory 6 and disposed subsequently to the GOP 
flag. 
The buffer memory control section 7 outputs a control signal for reading 
out video data for one picture frame to be MPEG decoded in a picture frame 
period from the video buffer memory 6 and outputs another control signal 
for reading out video data of a predetermined number of picture frames 
temporarily stored in the video display frame memory 100 of the video 
display processing section 10 one by one picture frame in the same picture 
frame period under the control of the CPU control section 25. 
The audio buffer memory 19 temporarily stores an audio stream inputted 
thereto from the audio packet output port of the PES packet processing 
section 4. 
The AV synchronization timing production section 20 produces an AV 
synchronization timing signal for synchronization of video and audio data 
of MPEG decoded data in response to intra-apparatus time information 
outputted from the time information production section 16, and supplies 
the AV synchronization timing signal to the video MPEG decoding section 8 
and the audio MPEG decoding section 21. 
The audio MPEG decoding section 21 MPEG decodes an audio stream read out 
from the audio buffer memory 19 under the control of the host CPU 18 via 
the CPU bus 17 and the host memory 23. 
The audio D/A conversion section 22 performs digital to analog conversion 
of decoded audio data outputted from the audio MPEG decoding section 21 
and sends out the resulting analog data to the video viewer. 
The CPU control section 25 receives an intra-apparatus clock signal from 
the clock generation section 15, intra-apparatus time information from the 
time information production section 16, a GOP detection signal from the 
GOP detection section 5 and an error information signal from the error 
information processing section 14 and controls the host CPU 18 via the CPU 
bus 17 and the host memory 23 to effect control and transfer of data to 
and from the video MPEG decoding section 8, the audio MPEG decoding 
section 21, the buffer memory control section 7 and so forth. Further, the 
CPU control section 25 controls sending out of error information such as a 
request signal for requesting for re-sending of video data of a picture 
frame, with which a data error such as a miss of data has occurred, or for 
stopping of sending out of video data to the MPEG coding multiplexing side 
via a line interface section 24. 
FIG. 2 illustrates an example of multiplexing when, for example, a moving 
picture signal, an audio signal and other signals (for example, a 
character data signal) of multimedia on-demand information are 
multiplexed. FIG. 3 illustrates an example of a coding order in one GOP of 
an I picture, P pictures and B pictures where one GOP includes 15 frames 
and an inter-picture prediction method between pictures. FIG. 4 
illustrates an example of a stream data array of an MPEG coded bit stream. 
Referring to FIG. 1 to 4, when a plurality of MPEG coded bit streams of 
moving picture data, audio data, character data and some other data of 
multimedia on-demand information are to be transmitted to a viewer side 
via a transmission line, data of the bit streams within substantially the 
same time periods are collected to form a packet, and a plurality of such 
packets are individually time division multiplexed to form a plurality of 
packs. 
FIG. 2 illustrates an example of data structure wherein video data of 
moving pictures are delineated into data V1, V2, . . . on the time base 
while audio data 1 of the sound (for example, the right side sound of the 
stereo sound) are delineated into data A11, . . . , A16, . . . and audio 
data 2 of the sound (for example, the left side sound of the stereo sound) 
are delineated into data A21, . . . , A25, . . . , and other data such as, 
for example, character data to be inserted in a screen are delineated into 
data AUX1, . . . , AUX4, . . . 
Here, if the data V1, V2, . . . of the video data are determined as video 
packets V1, V2, . . . respectively, then the video packets V1, V2, . . . 
make a reference for construction of packets of the other audio and 
character data. In particular, taking the packet construction for the 
audio data 1 as an example, from among the data A11 to A16 of the video 
data 1, the data A11 to A13 which are within substantially the same time 
periods as the time period the video data V1 are collected to form a first 
audio 1 packet #1, and the data A14 and A15 which are within substantially 
same time period as the time period the video data V2 are collected to 
form a second audio 1 packet #2. Thus, a stream which includes the audio 1 
packet #1, the audio 1 packet #2, . . . is produced, and the audio 1 
packet #1 and the audio 1 packet #2 of the stream correspond to a PES 
packet #2 in the pack layer shown in FIG. 4. 
The video packets #1, #2, . . . , audio 1 packets #1, #2, . . . , audio 2 
packets #1, #2, . . . and character packets #1, #2, . . . constructed in 
this manner are time division multiplexed such that the first packets (#1) 
of them are time division multiplexed and the second packets (#2) of them 
are time division multiplexed (here, for the convenience of decoding, 
video data, audio data and character data are multiplexed in this order) 
to construct a pack #1 and another pack #2, respectively. Thus, a pack 
stream which corresponds to the uppermost layer shown in FIG. 4 is formed 
from the packs #1, #2, . . . 
It is to be noted that a packet header for each medium of a PES packet 
includes time stamp PTS code information which makes a reference to time 
information which is used to establish synchronism among the media upon 
decoding by the decoding side and so forth. 
FIG. 3 illustrates an array of picture frames which construct one GOP of 
compression coded pictures in one video packet and particularly shows an 
example wherein one GOP is formed from 15 picture frames. In particular, 
one GOP is composed of one I picture frame I1 always disposed at the top 
of the GOP and making a base for predictive coding of the other picture 
frames, four P picture frames P1 to P4 formed by forward predictive coding 
from the I picture frame and ten B picture frames B1 to B10 formed by 
bidirectional coding from the I picture frame and the next P picture frame 
or from two adjacent ones of the P picture frames. Upon decoding, the 
pictures are decoded in order of I1, B1, B2, P1, . . . , B10. The picture 
stream of the video PES packet #1 in the PES packet layer of FIG. 4 is 
shown including the I1, B1, B2, P1 and B3 pictures of FIG. 3, and a 
picture start code which indicates the start of a picture is added to the 
top of each of the picture frames. 
Subsequently, operation of the MPEG coded picture decoding apparatus will 
be described. 
An MPEG coded and multiplexed pack stream of the uppermost layer, that is, 
an MPEG multiplexed bit stream, is inputted to the MPEG coded picture 
decoding apparatus via a transmission line such as, for example, a high 
speed digital private line and stored into the stream buffer memory 1 via 
the line interface section 26. 
The buffer memory control section 2 controls the stream buffer memory 1 in 
response to a GOP detection signal from the GOP detection section 5 
detected from a GOP flag of a video PES packet of the PES packet layer, 
and reads out, each time such GOP flag is detected, stream data of a pack 
packet from which the GOP has been detected. 
The pack header processing section 3 separates a pack header of the pack 
layer read out from the stream buffer memory 1 based on a pack start code 
and a stream ID code in the header, extracts SCR code information for a 
system clock reference disposed in the separated header, and supplies the 
SCR code information to the clock generation section 15 which produces an 
intra-apparatus clock signal to be used on the decoding side. 
The PES packet processing section 4 separates a PES packet header from the 
PES packet stream, which is inputted from the pack header processing 
section 3 and from which the pack header has been separated, based on the 
packet start code and the stream ID code in the PES packet header disposed 
at the top of each PES packet, extracts PTS code information, which makes 
a reference for time information, disposed in the separated PES packet 
header, and supplies timing information to the time information production 
section 16, for example, for synchronization between coded video data and 
coded audio data to be used on the decoding side. Further, the PES packet 
processing section 4 separates the PES packet stream into PES packets for 
individual media (in FIG. 1, the construction for separation of character 
PES packets is omitted for convenience of illustration), and outputs video 
PES packets to the video output port, outputs audio 1 PES packets and 
audio 2 PES packets to the audio output port and outputs video PES 
packets, from which packet headers have been separated, to the GOP output 
port. 
Then, the video buffer memory 6 stores the picture stream of the video PES 
packets input thereto from the video output port of the PES packet 
processing section 4 while the audio buffer memory 19 stores the audio 
stream of the audio PES packets inputted thereto from the audio output 
port. 
The GOP detection section 5 detects, from a video PES packet which has been 
input thereto from the GOP output port of the PES packet processing 
section 4 and from which the PES packet headers have been separated, a GOP 
flag arranged at the top of the video PES packet and outputs and supplies 
the GOP flag as a GOP detection signal to the buffer memory control 
section 2 in order to allow production of a timing at which the individual 
stream data are to be read out from the stream buffer memory 1 and the 
video buffer memory 6 after each GOP period. Here, although the first GOP 
flag is not detected unless the first pack packet is read out from the 
stream buffer memory 1, even if the stream buffer memory 1 is not 
controlled to read out data therefrom, since data are discharged from the 
stream buffer memory 1 beginning with data stored first when data are 
stored by more than a predetermined amount, the first GOP flag of the 
first pack stream is detected with certainty. 
Consequently, the buffer memory control section 2 performs reading of the 
stream buffer memory 1 described above and simultaneously performs reading 
control of the video buffer memory 6. In particular, while data are read 
out from the video buffer memory 6 in units of a video PES packet after 
each GOP period under the control of the buffer memory control section 2, 
those data to be actually output to the video MPEG decoding section 8 are 
read out in units of a picture after each picture frame period under the 
control of the buffer memory control section 7. 
The video MPEG decoding section 8 MPEG decodes a picture stream data read 
out in units of one picture frame and in order of the picture array in one 
GOP of FIG. 3 from the video buffer memory 6 and stores the decoded 
picture stream data into the picture decoded data frame memory 90 which is 
a one frame memory (for example, in the NTSC video system of MPEG2, a 
memory for information of 720.times.480 pixels) of the decoded data 
storage section 9. 
The memory management section 91 of the decoded data storage section 9 
outputs, after the decoded data for one picture frame inputted thereto 
from the video MPEG decoding section 8 are stored fully or regularly into 
the picture decoded data frame memory 90, the picture decoded data for the 
one picture frame so that they may be stored into the video display frame 
memory 100 of the video display processing section 10. Here, if decoded 
data for one frame are not fully or regularly stored into the picture 
decoded data frame memory 90, that is, if some picture decoded data 
misses, then the memory management section 91 outputs, together with an 
error detection signal, error information such as information of a picture 
position of the picture frame, which suffers from the miss of data, 
detected by counting an order number of storages of decoded data starting 
from a time at which I picture decoded data were stored together with 
start code information. On the other hand, when all picture decoded data 
are stored fully or regularly, the memory management section 91 outputs a 
regular storage signal upon completion of the storage and simultaneously 
outputs the stored picture decoded data to the video display frame memory 
100. 
Regular picture decoded data output from the picture decoded data frame 
memory 90 are stored for several picture frames into the video display 
frame memory 100 of the video display processing section 10. Otherwise, if 
an error detection signal of a data miss is output from the memory 
management section 91 and a picture re-sending request signal from the 
error information processing section 14 is sent out to the MPEG coding 
multiplexing side via the CPU control section 25 and then, before data are 
re-sent in response to the re-sending request and MPEG decoded and stored 
into the picture decoded data frame memory 90 again, the picture decoded 
data for several picture frames which have been stored in the video 
display frame memory 100 until then are read out so as to be displayed on 
a screen, then when the next picture frame with which the data miss has 
occurred is displayed on the screen, a pause condition is entered while 
the display screen remains displaying a screen of the immediately 
preceding picture frame and pictures for several picture frames will miss 
in the pause condition. Therefore, in order to assure sufficient time 
after a re-sending request until completion of storage of re-sent picture 
decoded data, picture decoded data for a required number of picture frames 
are stored into the video display frame memory 100. 
Then, the display control section 101 of the video display processing 
section 10 outputs picture decoded data read out for each one picture 
frame from the video display frame memory 100 so as to be displayed on the 
screen after each picture frame period under the control of the buffer 
memory control section 7 to the video D/A conversion section 12 in 
response to a video display timing signal supplied thereto from the 
display timing production section 11. 
Here, the video display timing signal output from the display timing 
production section 11 is, for example, a frame signal of the period of 
1/30 second which is a video vertical synchronizing signal of the NTSC 
system. 
The frame check detection section 13 supervises the output of the memory 
management section 91 of the picture decoded data frame memory 90 after 
each period of the video display timing signal supplied thereto from the 
display timing production section 11, and outputs nothing if a correct 
storage signal is received at each video displaying timing, but outputs, 
if an error detection signal is received at a video display timing, error 
information to the error information processing section 14 together with 
an error detection signal. 
The error information processing section 14 produces a video re-sending 
request signal for requesting for re-sending of the video data of the 
picture frame, with which the error has occurred, or for re-sending of one 
GOP including the picture frame to the MPEG coding multiplexing side via 
the CPU control section 25 based on the error information including 
picture position information supplied thereto from the memory management 
section 91 via the frame check detection section 13, and supplies the 
video re-sending request signal to the CPU control section 25. 
The CPU control section 25 controls the video MPEG decoding section 8, the 
audio MPEG decoding section 21 and the buffer memory control section 7 via 
the host memory 23 and the host CPU 18 in response to the intra-apparatus 
clock signal from the clock generation section 15, the intra-apparatus 
time information from the time information production section 16, the GOP 
signal from the GOP detection section 5 and so forth to effect control of 
MPEG decoding processing, reading processing from the buffer memory and so 
forth. Further, the CPU control section 25 develops a re-sending request 
for video data of the picture frame, with which the data miss has 
occurred, or for video data of one GOP including the picture frame to the 
MPEG coding multiplexing side via the line interface section 24. 
It is to be noted that the error processing of the error information 
processing section 14 may include not only delivery of a video re-sending 
request for a picture frame with which a data miss has occurred, or for a 
GOP including the picture frame but also delivery of a request for 
stopping the sending out of the following video data when an error is 
detected with an I picture or a P picture. In particular, if, for example, 
a miss of data occurs on the coding side and this error is not detected on 
the coding side and is sent out without being corrected, then if the miss 
of data occurs with an I picture or a P picture, there is the possibility 
that a miss or an error of data may occur also with a P picture and B 
pictures which are predictively coded based on the I picture or with B 
pictures predictive coded based on the P picture. Therefore, in order to 
prevent an influence of the miss or error of data upon a screen display, a 
request to stop sending video data is delivered when an error is detected 
with an I picture or a P picture. 
Having now fully described the invention, it will be apparent to one of 
ordinary skill in the art that many changes and modifications can be made 
thereto without departing from the spirit and scope of the invention as 
set forth herein.