mpegtsmux, high overhead for a small aac bitrate

[Sebastian Dröge]

On Mi, 2016-05-18 at 11:13 +0200, Vincent Génieux wrote:
> Hi all,
> 
> 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
> 
> 
> Do you have any idea on how I could reduce the bitrate of the ts stream 
> in my pipeline ?

Can you file a bug about this at
  https://bugzilla.gnome.org/enter_bug.cgi?product=GStreamer
?

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.

-- 
Sebastian Dröge, Centricular Ltd · http://www.centricular.com
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