[Libav-user] libavformat RTP management

[William MANCON]

The output with ffplay :

[sdp @ 0x1313800] All info found
[sdp @ 0x1313800] Estimating duration from bitrate, this may be inaccurate
Input #0, sdp, from 'sdp.foo':
  Metadata:
    title           : No Name
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0.0, 21, 1/90000: Video: vp8, yuv420p, 640x480, 1/90000, 30
tbr, 90k tbn, 90k tbc

It seems to detect the resolution and codec config. It's strange that the
screen display a black video.

On Fri, Oct 23, 2015 at 7:24 PM, William MANCON <wmancon at gmail.com> wrote:

> I used av_sdp_create to get the correct SDP. this function gave me :
> 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 53.21.1
> m=video 5000 RTP/AVP 96
> b=AS:128
> a=rtpmap:96 VP8/90000
>
> And after that i tried to write the stream to a file using :
>
> ffmpeg -i sdp.foo  -c:v copy  output.webm -loglevel debug
>
> This is the output :
>
> Applying option loglevel (set logging level) with argument debug.
> Successfully parsed a group of options.
> Parsing a group of options: input file sdp.foo.
> Successfully parsed a group of options.
> Opening an input file: sdp.foo.
> [sdp @ 0x442a320] Format sdp probed with size=2048 and score=50
> [sdp @ 0x442a320] video codec set to: vp8
> [udp @ 0x4431780] end receive buffer size reported is 131072
> [udp @ 0x4431580] end receive buffer size reported is 131072
> [NULL @ 0x4430e20] setting jitter buffer size to 500
> [sdp @ 0x442a320] Before avformat_find_stream_info() pos: 143 bytes
> read:143 seeks:0
> [sdp @ 0x442a320] Received no start marker; dropping frame
>
>
> It look likes ffmpeg do not read data on the line ?!
>
> After launching the command It seems to wait for something, I wait few
> minutes and I do a Ctrl+c
>
> then the output is :
>
> [sdp @ 0x442a320] Could not find codec parameters for stream 0 (Video:
> vp8, 1 reference frame, yuv420p): unspecified size
> Consider increasing the value for the 'analyzeduration' and 'probesize'
> options
> [sdp @ 0x442a320] After avformat_find_stream_info() pos: 143 bytes
> read:143 seeks:0 frames:0
> sdp.foo: could not find codec parameters
> Input #0, sdp, from 'sdp.foo':
>   Metadata:
>     title           : No Name
>   Duration: N/A, bitrate: N/A
>     Stream #0:0, 0, 1/90000: Video: vp8, 1 reference frame, yuv420p, 90k
> tbr, 90k tbn, 90k tbc
> Successfully opened the file.
> Parsing a group of options: output file output.webm.
> Applying option c:v (codec name) with argument copy.
> Successfully parsed a group of options.
> Opening an output file: output.webm.
> Output #0, webm, to 'output.webm':
> Output file #0 does not contain any stream
> [AVIOContext @ 0x4432da0] Statistics: 143 bytes read, 0 seeks
>
> I do not understant "sdp.foo: could not find codec parameters"
>
> Someone have an idea of what append ?
>
> If I try with ffplay : ffplay sdp.foo
> A windows apprear but the video is a black screen. Nothing else.
>
> Do someone understand what's happening ?
>
> On Fri, Oct 23, 2015 at 3:02 PM, William MANCON <wmancon at gmail.com> wrote:
>
>>
>> Just to make sure: On this mailing list, only the
>>> libraries from the FFmpeg project are supported.
>>>
>>
>> > Yes,
>>
>> I suspect the payload descriptor is not added by
>>> the encoder function (which is in libavcodec) but
>>> by the muxer (in libavformat).
>>>
>>> You should be able to use ffmpeg (the command line
>>> tool) to test.
>>>
>>> >I tried but  without the correct sdp it fail. I Maybe need to set the
>> correct payload type in the code.
>> I tried with this 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 55.22.100
>> m=video 1234 RTP/AVP 96
>> b=AS:200
>> a=rtpmap:96 VP8/90000
>> a=fmtp:96 apt=100
>>
>> with no luck. the stream is outputted at rtp://127.0.0.1:5000 do i need
>> the port to the sdp ?
>>
>> Thanks Carl for your comment.
>>
>> William.
>> _______________________________________________
>> Libav-user mailing list
>> Libav-user at ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/libav-user
>>
>>
>
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