[FFmpeg-devel] Fwd: Transcode VP8 RTP stream to mpeg1 video frames.

Ajay Choudary ajay6ft at gmail.com
Wed May 20 12:49:36 CEST 2015

Hi All,

Am trying to stream the MPEG video on html5 canvas tag.

I was able to stream my Web CAM video in browser (canvas video tag) with
below command. (No errors & good quality)
# ffmpeg -s 640x480 -f video4linux2 -i /dev/video0 -f mpeg1video -b 800k -r
30 *
I was also able to stream VP8 (webm) file in browser with below command.
ffmpeg -vcodec libvpx -i output2.webm -f mpeg1video -b: 400k -r 25

When i try to stream video from active RTP channel,
Transcode steps:
-> Read RTP from socket, decode from vp8 codec to native/raw rtp.
-> Encode it to mpeg1video frames.
-> And send the frame through socket (webserver).

Note: Here am handling video stream only, as i don't have other streams
like audio or data.

Am getting below errors,
*# ffmpeg -vcodec vp8 -i rtp://
<>  -f mpeg1video -b: 400k -r 25
ffmpeg version n2.5.6-3-ga2ad7fd Copyright (c) 2000-2015 the FFmpeg
  built on May  1 2015 13:18:01 with gcc 4.4.7 (GCC) 20120313 (Red Hat
  configuration: --enable-nonfree --enable-gpl --enable-libvpx
--enable-decoder=aac --enable-libx264 --enable-demuxer=mov --enable-x11grab
--enable-zlib --enable-protocol=http --enable-filter=aformat
--enable-filter=volume --enable-filter=aresample --prefix=/usr/
  libavutil      54. 15.100 / 54. 15.100
  libavcodec     56. 13.100 / 56. 13.100
  libavformat    56. 15.102 / 56. 15.102
  libavdevice    56.  3.100 / 56.  3.100
  libavfilter     5.  2.103 /  5.  2.103
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
[rtp @ 0x25cf0e0] Unable to receive RTP payload type 100 without an SDP
file describing it
Input #0, rtp, from 'rtp://':
  Duration: N/A, bitrate: N/A
Codec AVOption b (set bitrate (in bits/s)) specified for output file #0 ( has not been used for any stream.
The most likely reason is either wrong type (e.g. a video option with no
video streams) or that it is a private option of some encoder which was not
actually used for any stream.
Output #0, mpeg1video, to '':

ffmpeg is reading rtp and detecting payload value (VP8 = 100), i try to
provide sdp file with  *-sdp_file option * but it is invalid argument.

please suggest me, how to resolve these errors.

Thanks & Regards,

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