[FFmpeg-devel] RTP input stream blocks ffmpeg
Thu Sep 20 12:34:11 CEST 2007
Thank you for your answer, thank you for helping ffmpeg-newbies like me...
Luca Abeni a ?crit :
> I believe this question belongs to ffmpeg-users, anyway:
> Yohann Martineau wrote:
>> I'm trying to transcode a video stream sent over RTP from h263 to
>> mpeg2video, and to forward this transcoded stream over RTP.
> AFAIK, ffmpeg does not support receiving h.263 in RTP (support for the
> h.263 payload is not implemented).
Yes, it seems that it's not possible directly. But I made a capture of
my stream with wireshark, dumped the h263 payload in a raw file and
opened this raw file successfully with ffmpeg (and with ffplay), giving
the appropriated format/codec info:
$ ffmpeg.exe -f h263 -vcodec h263 -i h263.raw
Thus, I thought it was possible to open this raw stream from network
instead of file. I wrote a small application in java that takes my
RTP/H263 stream as input and dumps the raw payload on another port. But
I don't know if it's possible to specify ffmpeg a port on which it
should listen for incoming packets...
>> The following command gets stuck:
>> $ ffmpeg.exe -i rtp://192.168.1.45:10002
> I suspect this command line is wrong. You need to use an rtsp:// url, or
> to provide an SDP file.
You're right, I just discovered that it was possible to give a .sdp text
file as input to ffmpeg...
So I tried several commands to stream my video and receive it with ffmpeg.
Here is the first command I used to stream my video:
$ ffmpeg.exe -f h263 -vcodec h263 -i h263.raw -f rtp
This command gives me a session description:
o=- 0 0 IN IPV4 127.0.0.1
c=IN IP4 192.168.1.45
m=video 10002 RTP/AVP 34
I put this in a text file called test.sdp.
Then I provide this file as input for ffmpeg:
$ ffmpeg.exe -i test.sdp
And I launch my previous streaming command. ffmpeg then finds the video
stream and ask me for an output file. great.
But when I try to transcode and stream with the following command:
$ ffmpeg.exe -f h263 -vcodec h263 -i h263.raw -f rtp -vcodec mpeg2video
The ffmpeg instance that receives packets says nothing.
Diving into SDP, i saw that the media attribute of the sdp generated
without '-vcodec mpeg2video' gives a payload type of 35, which
corresponds to H263. This is ok. When I launch the command with '-vcodec
mpeg2video', the payload type is 96, which is a dynamic payload type.
But there is no a=rtpmap:96 ... in the sdp generated.
If I launch the command with '-vcodec mpeg4', here is the end of the SDP:
m=video 10002 RTP/AVP 96
This one is ok. The dynamic payload type is described in an attribute.
>> I try to get codec information from this command line. But I have
>> nothing on my console.
> Maybe you even wrote the wrong IP:port. Note that you likely need to
> specify "?local_port=..." in the url.
Once again: thank you.
Asterisk was "the future of telephony", but ffmpeg is "the future of
> ffmpeg-devel mailing list
> ffmpeg-devel at mplayerhq.hu
More information about the ffmpeg-devel