[FFmpeg-devel] AAC - Fetching data out of data stream elements/DSE?

[Carsten Gross]

Hello,

AAC audio streams offer the possibility of transmitting additional binary
data with the audio data. The corresponding element is called a "data
stream element" (DSE). On the new ARD satellite audio transponder on
Astra 19.2E, this is used by NDR, for example, to transmit RDS (Radio
Data System). The audio format used is AAC-LATM.

In the current ffmpeg git code, DSE are skipped. I have included a
HexDump of the DSE data in libavcodec/aacdec_template.c (by changing
skip_data_stream_element()) for testing and in the Hexdump I see exactly
the data I would like to get out of the audio data stream into my
application "ts2shout" with the help of ffmpeg libavcodec. 

If I want to implement DSE support, what is the right "ffmpeg-"way to
provide this binary data embedded in the audio frames to a user
application? Metadata seems to be more for "static" properties of files
and it is text only.

Would using "AVFrameSideData" be the right method to transfer the data
to the user application? Is there a generic data type, or would I have
to define a new one in AVAudioServiceType, regarding that it is possible
to have more then one DSE in one audio frame? My plan would be to later
pass the individual AAC frames to libavcodec for decoding (like it is
described in the example in doc/examples/decode_audio.c) and possibly
only evaluate the respective DSE.

Regards,

   Carsten

More about ts2shout:
https://github.com/carsten-gross/ts2shout

-- 
Carsten Gross            | http://www.siski.de/~carsten/