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• How is video decoding corruption debugged ?

  20 novembre 2013, par TopGunCoder

  I just started working for a new company and my new role demands that I help debug the video corruption that they are receiving through decoding frames. As much as I intend on digging down deep into the code and looking into the specifics of my problem, it made me think about video debugging in general.

  Since handling videos is very new to me, the whole process seems pretty complex and it seems there are a lot of places for corruption to present itself. The way I see it there is at least three places where corruption could pop up (barring memory corruption from the machine) :

  • Transporting the data before it is decoded
  • decoding implementation that perpetuates corruption once it is encountered, or is all together incorrect (Which seems to be my problem)
  • Transportation to the monitor(which seems unlikely but possible)

  So what i'm really curious about is if/how people debug their video streams to determine the location of any potential corruption they are encountering. I'm sure there is no sure fire method but I am curious to see what problems are even possible and how they can be identified and triaged.

  P.S. - I'm not sure of the differences between different decoding methods but, if this question seems too vague maybe it helps to mention I am using ffmpeg and avcodec_decode_video2 for the decoding.

• Multiple Video Streams in one Feed ffmpeg

  1er février 2014, par trueblue

  We are trying to send live stream from two webcams as below :

  ffmpeg -f video4linux2 -i /dev/video0 -f video4linux2 -i /dev/video1 http://127.0.0.1:8090/feed1.ffm

  We want to play both the streams using any players available. When we use VLC, to open the stream, we get only one stream( from /dev/video0). The command is as below :

  vlc http://127.0.0.1:8090/test.mpg

  Here I am running ffserver in my machine and trying to access as localhost. My ffserver config is as below :

  Port 8090
  
  BindAddress 0.0.0.0
  
  MaxHTTPConnections 2000
  
  MaxClients 1000
  
  MaxBandwidth 1000
  
  CustomLog -
  
  NoDaemon
  
  
  
  <feed>
  
  File /tmp/feed1.ffm
  
  FileMaxSize 1G
  
  ACL allow 127.0.0.1
  
  </feed>
  
  
  
  <stream>
  
  
  
  # coming from live feed &#39;feed1&#39;
  
  Feed feed1.ffm
  
  Format mpeg
  
  VideoBufferSize 40000
  
  VideoSize 1280x720
  
  VideoCodec mpeg1video
  
  NoAudio
  
  ACL ALLOW 127.0.0.1
  
  </stream>
  
  
  
  <stream>
  
  Format status
  
  
  
  # Only allow local people to get the status
  
  ACL allow localhost
  
  ACL allow 192.168.0.0 192.168.255.255
  
  
  
  #FaviconURL http://pond1.gladstonefamily.net:8080/favicon.ico
  
  </stream>
  
  
  
  
  
  # Redirect index.html to the appropriate site
  
  
  
  <redirect>
  
  URL http://www.ffmpeg.org/
  
  </redirect>

  If we try the below command to save two streams onto the file, we are getting two instances of VLC player and both Streams can be seen :

  ffmpeg -f video4linux2 -i /dev/video0 -f video4linux2 -i /dev/video1 /home/2Streams.mpg

  Its a strange behavior I am able to save two Video Streams as a file but I am unable to send Two Video Streams in one Single feed. Kindly help me out in achieving the same.

  Regards

• ffmpeg unable to find encoder 'libvorbis'

  15 juillet 2014, par scientiffic

  I’m unable to transcode a video file to webm because my machine isn’t able to find libvorbis. When I run the following command :

  ffmpeg -y -i /public/uploads/tmp/1382112521-11953-7661/webm_Untitled.mov -vcodec libvpx -acodec libvorbis -s 640x360  -b 1500k -ab 160000 -f webm -g 30 -aspect 1.7777777777777777 /public/uploads/tmp/1382112521-11953-7661/tmpfile.webm

  I get the error

  Unknown encoder 'libvorbis'

  I already have libvorbis installed on my machine, though (When I try "brew install libvorbis, it tells me : Warning : libvorbis-1.3.3 already installed).

  How can I solve this problem ?

  Here is the full log :

  ffmpeg -y -i /public/uploads/tmp/1382112521-11953-7661/webm_Untitled.mov -vcodec libvpx -acodec libvorbis -s 640x360  -b 1500k -ab 160000 -f webm -g 30 -aspect 1.7777777777777777 /public/uploads/tmp/1382112521-11953-7661/tmpfile.webm
  
  ffmpeg version 1.2.1 Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Oct 18 2013 12:20:19 with Apple LLVM version 4.2 (clang-425.0.28) (based on LLVM 3.2svn)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/1.2.1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --enable-avresample --enable-vda --cc=cc --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid --enable-libvpx
  
    libavutil      52. 18.100 / 52. 18.100
  
    libavcodec     54. 92.100 / 54. 92.100
  
    libavformat    54. 63.104 / 54. 63.104
  
    libavdevice    54.  3.103 / 54.  3.103
  
    libavfilter     3. 42.103 /  3. 42.103
  
    libswscale      2.  2.100 /  2.  2.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  2.100 / 52.  2.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/public/uploads/tmp/1382112521-11953-7661/webm_Untitled.mov':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 0
  
      compatible_brands: qt  
  
      creation_time   : 2013-09-27 20:08:57
  
    Duration: 00:00:02.14, start: 0.000000, bitrate: 17460 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080, 17292 kb/s, 29.88 fps, 29.83 tbr, 90k tbn, 180k tbc
  
      Metadata:
  
        creation_time   : 2013-09-27 20:08:57
  
        handler_name    : Core Media Data Handler
  
      Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 123 kb/s
  
      Metadata:
  
        creation_time   : 2013-09-27 20:08:57
  
        handler_name    : Core Media Data Handler
  
  Please use -b:a or -b:v, -b is ambiguous
  
  Unknown encoder 'libvorbis'