[FFmpeg-user] Strange behaviour with HLS to ISMV?

[Nicky Gerritsen]

Hi all,

We are testing ingesting an HLS source into an ISMV server using ffmpeg.
However, we found something strange:

ISMV has CodecPrivateData which contains information about the codec
data. Now it seems that something goes wrong here:

It seems to somehow infer the profile ID wrongly. An example
CodecPrivateData:

HLS source:
CodecPrivateData:
00000001091000000001674D401F96520080093602A100000300010000030032E0A000F42400040167F18E3050007A12000200B3F8C70ED0B168900000000168EB7352

When using an RTMP stream as source, the CodecPrivateData misses the
000000010910 part.
It seems this part is responsible for the profile ID as far as I have found.
0910 seems to produce avc1.16.30 as output, whereas the input is avc1.77.30.
Even stranger: we use software which automatically can stream HLS again
from the ISMV. If I then use the output HLS stream and ingest it again,
it gets yet another profile ID it seems. The CodecPrivateData now starts
with 00000001 Konsole output 09F0.

I tried looking in the code where this part of the codec private data
came from, but as far as I can find this comes kinda directly from ID3
data in the source HLS stream.

I'm not entirely sure what is going wrong, but I did find if I remove
the first 6 bytes from the private data completely everything does work
fine.

Does anyone know what is going wrong and possible have a solution?

I tested with both ffmpeg 2.6.4 and the latest git code.

Regards,
--
Nicky Gerritsen
StreamOne