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mpegtsmux, high overhead for a small aac bitrate

Submitted by Vincent Génieux

Link to original bug (#766618)

Description

I am facing an issue with the following pipeline :

audiotestsrc num-buffers=100000 ! audio/x-raw,channels=2 ! voaacenc
bitrate=32000 ! mpegtsmux ! filesink location=test.ts

The tsdemux generate a stream with a huge bitrate compared to other
containers, such as mp4mux :

audiotestsrc num-buffers=100000 ! audio/x-raw,channels=2 ! voaacenc
bitrate=32000 ! mp4mux ! filesink location=test.mp4

$ ls -lh test.*
-rw-r--r-- 1 vincent vincent 9.6M May 18 10:56 test.mp4
-rw-r--r-- 1 vincent vincent 26M May 18 10:57 test.ts

I think there is a misconfiguration somewhere which leads the demux to
create very small chunk with many headers. I also noticed we can reduce
the size of the ts file with libav :

$ avconv -i test.ts -codec copy test2.ts
$ ls -lh *.ts
-rw-r--r-- 1 vincent vincent 26M May 18 10:57 test.ts
-rw-r--r-- 1 vincent vincent 9.8M May 18 11:03 test2.ts

The problem is most likely that we don't combine multiple AAC packets
into a single PES packet, and thus have a lot of overhead for each of
them. ffmpeg does this for audio at least if I remember the muxer code
correctly.