crtmpserver incorrectly believes that aac audio always stereo

[Alexey Tsarev]

Hello all,

I am tried to send web camera video/audio stream for ivideon server.

I found that ivideon hangs if I stream mono aac.

During debuging/investigation I found this line:

result += format("a=rtpmap:96 mpeg4-generic/%"PRIu32"/2\r\n", pInfo->_samplingRate);

in the file: sources/thelib/src/protocols/rtp/basertspappprotocolhandler.cpp

I sniffed traffic and got (marked bold):

v=0

o=- 648 0 IN IP4 10.1.1.1

s=myStream

u=www.rtmpd.com

e=con...@rtmpd.com

c=IN IP4 10.1.1.1

t=0 0

a=recvonly

a=control:*

a=range:npt=now-

m=audio 0 RTP/AVP 96

a=recvonly

a=rtpmap:96 mpeg4-generic/8000/2

a=control:trackID=1

a=fmtp:96 streamtype=5; profile-level-id=15; mode=AAC-hbr; config=158856e500; SizeLength=13; IndexLength=3; IndexDeltaLength=3;

m=video 0 RTP/AVP 97

a=recvonly

a=control:trackID=2

a=rtpmap:97 H264/90000

So crtmpserver incorrectly believes that aac audio always stereo.

https://tools.ietf.org/html/rfc3640 says that audio channels may omitted only in a case if only one channel present:

   a=rtpmap:<payload type> <encoding name>/<clock rate>[/<encoding
             parameters>]

   For audio streams, <encoding parameters> specifies the number of
   audio channels: 2 for stereo material (see RFC 2327 [5]) and 1 for
   mono.  Provided no additional parameters are needed, this parameter
   may be omitted for mono material, hence its default value is 1.

[Alexey Tsarev]

There is the solution:

result += format("a=rtpmap:96 mpeg4-generic/%"PRIu32"/%u\r\n",
pInfo->_samplingRate, pInfo->_channelsCount);

пятница, 25 марта 2016 г., 15:30:20 UTC+3 пользователь Alexey Tsarev написал: