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• rtsp stream capturing

  12 avril 2016, par ДМИТРИЙ МАЛИКОВ

  I’m looking for some universal way to dump rtsp stream. I want to figure out, that some rtsp stream is working well and server is sending some watchable video.

  openRTSP

  At first, google recommends me openRTSP tool.

   openRTSP -4 ${stream_link} > ${output_file}

  But output video file dumped by that tool is not really correct. Video decoder (ffdec) returns many errors like "Failed to decode video packet" and "[h264] no frame !", which don’t suit me.

  ffmpeg

  Then I’ve tried to dump rtsp stream with ffmpeg tool.

  ffmpeg -loglevel debug -i "${stream_link}" -s 640x480 -vcodec copy -acodec copy -y ${output_file}

  But streaming process was interrupted often by error :

  Application provided invalid, non monotonically increasing dts to muxer in stream 0: 730672 >= 730672
  
  av_interleaved_write_frame(): Invalid argument

  I’m trying to use --fflags igndts but ffmpeg doesn’t ignore these errors. It doesn’t make any sense, because that error actually means that audio and video streams are sending asynchronously. The worst thing is that dumped file, resulted by that interrupted dump, is not correct too. Ffdec return some error :

  ERROR [mov,mp4,m4a,3gp,3g2,mj2] moov atom not found
  
  ERROR [ffdec] av_open_input_file: Operation not permitted

  After a nice cup of googling I’ve found, that it’s really old ffmpeg’s muxer bug.

  mplayer

  Than I’ve tried to use mplayer with LIVE_555 lib.

  mplayer -noframedrop -dumpfile ${output_file} -dumpstream ${stream_link}

  But I’ve got some errors too.

  Stream not seekable!
  
  Core dumped ;)

  Question

  I think I’m doing something wrong. It’s sounds really ridiculous, that there is no way to save rtsp stream in correct and playable video-file.

  Maybe there are some another tools which can help with that task ? Actually, I will be grateful for any advice for all kind of libs and languages. But that process should be automatic and have cli.

  Refinements

  Something about 50% experiments I’ve done on the localhost with vlc-streamer that emulates rtsp-broadcaster. Here is a manual which I try to follow.

  I have really fresh and latest ffmpeg with x264 support, that I’ve installed by that useful thread.

• FFmpeg static keyframe rate

  7 novembre 2011, par 2di

  I have a question about ffmpeg usage. Every time when I trying to convert video files into
  some different format, output file getting static keyframe sequence.

  What I mean is that keyframes appear at the distance of 12 frames. I know that its controllerd by parameter -g that you can change to any other number.

  ffmpeg -i 1.avi -vcodec mpeg4 -b 2000000  out.avi

  I believe there should be some way to make keyframes appear on uneven intervals. These interval should be calculated by codec, and it should be based on image changes in the video file. So keyframes should be inserted only when they needed, but not consistently after N frames.

  Can somebody please explain to me how this "smart" encoding can be done with ffmpeg ?
  Thank you

  SOLUTION : ok what I'ev been looking for has very simple solution. If you set -g to zero, ffmpeg will choose keyframes based on the video shots and bitrate

• Trying to determine h.264 profile & level pragmatically

  23 juin 2012, par kryptobs2000

  Ideally the solution would be in python and cross platform, but that's probably not too likely, so all I require is it work in linux, and I can use a c extension to interface w/python if necessary. I see there is a python binding for ffmpeg which I was thinking about using, however I can't figure out how to determine the profile and level as it is, with fmmpeg or anything else, much less do it pragmatically. Google is not much help on the matter either.

  I've been able to determine what features I'd be looking for if I needed to determine the profile and levels manually then I can do that, but then that leads to the question, can ffmpeg then determine if the video was encoded with that feature set ? I guess what I'm wondering to that effect is, is it perhaps not possible to fully determine the level and specific profile after encoding ? I would think you'd have to know in order to decode it, but maybe not ; that would explain why I can't find any information on it. I've been toying with this on and off for awhile, but recently decided to consider a project I'd been thinking about, but this is one of this big things holding me back.