Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-11-23
2003-04-01
Jung, Min (Department: 2663)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S487000, C370S537000, C348S423100
Reexamination Certificate
active
06542518
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a transport generating apparatus for multiplexing video data and audio data and generating a transport stream corresponding to MPEG standard, and method thereof, and a program transmitting apparatus for transmitting a plurality of programs.
RELATED ART
In recent years, a digital satellite broadcasting system and a cable broadcasting system that transmit compressed video signals corresponding to MPEG
2
standard have been proposed and are being introduced all over the world. In the broadcasting world, DVB (Digital Video Broadcasting) standard proposed by an organization named DVB that was established for developing and standardizing a next-generation broadcasting system in Europe in around 1993 has become a defacto standard in digital broadcasting systems at the present time.
In the transmitting method corresponding to the DVB standard, video data and audio data contained in a program to be transmitted are encoded and thereby an encoded video stream and an encoded audio stream are generated. The encoded video stream and the encoded audio stream are converted into a transport stream that is transmitted. In other words, a transport stream is data of which an encoded video stream and an encoded audio stream are multiplexed.
To generate a transport stream of which an encoded video stream and an encoded audio stream have been multiplexed, a multiplexing unit that has an encoding function and a multiplexing function has been developed. In a conventional multiplexing unit, a video stream and a audio stream are multiplexed in a multiplexing period that is asynchronous with a frame period of the video stream and a frame period of the audio stream.
For example, when a video stream with a frame period of 33 msec and an audio stream with a frame period of 24 msec are multiplexed as shown in
FIG. 13
, in a conventional multiplexing unit, the video stream and the audio stream are multiplexed with the video frame period.
Next, with reference to
FIG. 13
, the conventional multiplexing process will be described. As shown in
FIG. 13
, in the first video frame period, an encoded video frame V
1
encoded in the first video frame period and encoded audio streams A
1
and A
2
encoded in the first video frame period are multiplexed. In the second video frame period, an encoded video stream V
2
encoded in the second video frame period and an encoded audio stream A
3
encoded in the second video frame period are multiplexed. In each video frame, such a multiplexing process is repeated. Thus, as is clear from
FIG. 13
, the data amount of the first transport stream generated in the first video frame period is relatively large. In contrast, the data amount of the second transport stream T
2
generated in the second video frame period is relatively small. In other words, in the conventional multiplexing process, the data amount of a transport stream generated varies in each video frame period.
To generate transport streams in such a manner that an STD (System Target Decoder) buffer of a decoder of a receiving unit that receives video streams and audio streams is prevented from overflowing, the conventional multiplexing unit that performs such a multiplexing process should perform simulations for the multiplexing process in various video frame periods. The STD buffer is a virtual buffer used to perform a decoding process for transport streams and to describe semantics of the transport streams.
Next, with reference to a flow chart shown in
FIG. 14
, a conventional process for generating a transport stream will be described.
At step S
100
, an encoded video stream V
1
is received from a video encoder in the first video frame period. In addition, encoded audio streams A
1
and A
2
are received from an audio encoder in the first video period.
At step S
101
, before the encoded video stream V
1
and the encoded audio streams A
1
and A
2
are multiplexed and a first transport stream T
1
is generated in the first video frame period, one multiplexing schedule on which the video stream V
1
and the audio streams A
1
and A
2
are multiplexed is planed.
At step S
102
, a transport stream is generated corresponding to the multiplexing schedule planed at step S
101
. A simulation is performed for determining whether or not the transport stream transmitted to a decoding unit causes a video STD buffer and an audio STD buffer of the decoder to overflow.
At step S
103
, corresponding to the result of the simulation, it is determined whether or not the video STD buffer and the audio STD buffer of the decoding unit overflow. When the determined result is Yes (namely, both the audio STD buffer and the video STD buffer do not overflow), the flow advances to step S
104
.
At step S
104
, the encoded video stream V
1
and the encoded audio streams A
1
and A
2
are multiplexed corresponding to the multiplexing schedule planed at step S
101
.
At step S
105
, a first transport stream T
1
is generated with the multiplexed streams.
When the determined result at step S
103
is No (namely, the video STD buffer and the audio STD buffer of the decoding unit overflow), the flow returns to step S
101
. At step S
101
, another multiplexing schedule is planed. The steps S
101
, S
102
, and S
103
are repeated until the determined result at step S
103
becomes “Yes”.
At step S
106
, “n” is incremented so as to generate a transport stream T
2
in the second video frame period. Thereafter, the flow returns to step S
100
.
As is clear from the flow chart of the conventional transport generating process shown in
FIG. 14
, a process for planning a new multiplexing schedule and performing a simulation corresponding to the planed schedule should be performed in each video frame period. This is because the data amount of encoded video data and the data amount of encoded audio data vary in each video frame period as described in FIG.
13
.
Moreover, in the simulating process, it is necessary to virtually determine whether the video STD buffer and the audio STD buffer overflow. Thus, the algorithm of the simulation becomes very complicated. Consequently, it takes a very long time to perform the simulation.
As described above, in the conventional unit, it takes a very long calculation time for processing transport streams. Thus, a supplied program cannot be multiplex-transmitted on real time basis. Especially, in digital satellite broadcasting systems and digital ground wave broadcasting systems, live programs are required to be transmitted on real time basis. However, in the transport generating algorithm of the conventional unit, it is difficult to transmit such live programs on real time basis.
DISCLOSURE OF THE INVENTION
The present invention is made from the above-described point of view. An object of the present invention is to generate a transport stream on real time basis in such a manner that an STD buffer of a decoding unit does not overflow.
In the transport stream generating apparatus according to the present invention, each of the data amount of an encoded video stream multiplexed in one video frame and the data amount of an encoded audio frame multiplexed in a predetermined period is almost constant in any video frame period. In addition, the data amount of a transport stream generated in one video frame period is almost constant in any video frame period.
Thus, the data amount of a transport stream that is output from the transport stream generating apparatus is constant in any frame period. Consequently, in the transport stream generating apparatus according to the present invention, it is not necessary to perform a simulation for determining whether or not a STD buffer of a decoding unit overflows. Thus, the transport stream generating apparatus according to the present invention can generate a transport stream faster than the conventional apparatus that requires a simulation. In addition, the apparatus according to the present invention can generate a transport stream on real time basis.
In the transport stream generating apparatus according to the present invention, schedu
Jung Min
Simon Darren M.
LandOfFree
Transport stream generating device and method, and program... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transport stream generating device and method, and program..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transport stream generating device and method, and program... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3113040