Multiplexing H.264/AVC Video with MPEG-AAC Audio Harishankar Murugan University of Texas at Arlington Outline : Multiplexing: Areas of applications Why H.264 and AAC? Multiplexing De-multiplexing Synchronization and Playback Results Conclusions Future work References
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University of Texas at Arlington
Anchor picture with only I-slices.
Encoder Block diagram of AAC
Only one header in the beginning of the file followed by raw data blocks
Separate header for each frame enabling decoding from any frame
AUDIO OR VIDEO ELEMENTARY STREAM
time = frame number/fps
Number of samples/frame (AAC) : 1024
time = 1024*frame number/(sampling rate)
Each elementary stream has a unique PID. Some are reserved for NULL packets and PSI (Program Specific Information).
Sequence parameter set and picture parameter set are sent as PSI at frequent intervals.
1 bit flag to indicate presence of PES header in the payload.
1 bit flag to indicate presence of any data other than PES data in payload.
4 bit rolling counter which is incremented by 1 for each consecutive TS packet of the same PID. To detect packet loss.
If adaptation field control bit is ‘1’, byte offset value of the start of the payload or the length of adaptation field is mentioned here.
fps = 25
PES length = 570
=> 1/25 = 40 ms
# of TS = round(570/185)
=> 40/4 = 10 ms
4 TS packets
15 16 16 16 15 1024 16
Aframe number = ( Vframe number * sampling rate) / (1024*fps)
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