[FFmpeg-trac] #8474(ffmpeg:new): rtcpport param doesn't add a=rtcp to SDP
FFmpeg
trac at avcodec.org
Wed Jan 15 20:47:10 EET 2020
#8474: rtcpport param doesn't add a=rtcp to SDP
----------------------------------+----------------------------------
Reporter: juannm | Type: defect
Status: new | Priority: normal
Component: ffmpeg | Version: 4.2
Keywords: rtp, sdp | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Summary of the bug:
It is possible to specify an RTCP port that is not the default RTP + 1.
For this, we just have to add the parameter "rtcpport" to the output URL:
{{{
rtp://127.0.0.1:5004?rtcpport=54321
}}}
However, FFmpeg is not adding the corresponding media-level attribute
"a=rtcp:54321" to the generated SDP file.
This seems like a bug to me instead of a missing feature, because in SDP,
the omission of the "a=rtcp" attribute is nominally equivalent to an
implicit presence of that attribute, where the value is RTP + 1.
So, in short, FFmpeg is generating an SDP where the RTCP port is wrong.
How to reproduce:
{{{
ffmpeg \
-re \
-i video.mp4 \
-an \
-c:v copy \
-f rtp \
-sdp_file video.sdp \
"rtp://127.0.0.1:5004?rtcpport=54321"
}}}
generates an SDP file, "video.sdp", with these contents:
{{{
SDP:
v=0
o=- 0 0 IN IP4 127.0.0.1
s=No Name
c=IN IP4 127.0.0.1
t=0 0
a=tool:libavformat 58.29.100
m=video 5004 RTP/AVP 96
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1; sprop-parameter-
sets=Z0LAH9kAUAW7ARAAAD6QAAu4CPGDJIA=,aMuMsg==; profile-level-id=42C01F
}}}
Expected SDP would NOT have the invalid first line "SDP:" (that's a
different bug: #7068), and also it would have the "a=rtcp" line:
{{{
v=0
o=- 0 0 IN IP4 127.0.0.1
s=No Name
c=IN IP4 127.0.0.1
t=0 0
a=tool:libavformat 58.29.100
m=video 5004 RTP/AVP 96
a=rtcp:54321
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1; sprop-parameter-
sets=Z0LAH9kAUAW7ARAAAD6QAAu4CPGDJIA=,aMuMsg==; profile-level-id=42C01F
}}}
Full, uncut console output generated with '-report' and provided in the
attached file.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/8474>
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