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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.

• installing yasm / nasm on heroku with vulcan

  21 novembre 2013, par scientiffic

  I'm trying to do a build of ffmpeg on Heroku, and I need to use libvpx. In order to install libvpx, I need to have nasm or yasm. I tried installing both using vulcan, but I keep getting the error Neither yasm not nasm has been found

  Here is what I did

  Installing Nasm

  • get nasm source from http://www.linuxfromscratch.org/blfs/view/svn/general/NASM.html
  • tar file using : tar -xJf nasm-2.10.09.tar.xz
  • build using : vulcan build -v -s . -c "./configure -prefix=/app/vendor/nasm && make && make install"
  • add the output of the tar file from vulcan to vendor/nasm
  • push to heroku

  Installing Yasm

  • get yasm source from http://www.linuxfromscratch.org/blfs/view/svn/general/yasm.html
  • extra tar file and build using : vulcan build -v -s . -c "./configure -prefix=/app/vendor/yasm && make && make install"
  • add the output of the tar file from vulcan to vendor/yasm
  • push to heroku

  Installing Libvpx

  • get libvpx source from http://www.linuxfromscratch.org/blfs/view/svn/multimedia/libvpx.html
  • build libvpx using : vulcan build -v -s . -c "./configure —enable-shared —disable-static —prefix=/app/vendor/llibvpx && make && make install"

  Attemping to build libvpx yields this error :

  Packaging local directory... /.rvm/gems/ruby-1.9.2-p320/gems/vulcan-0.8.2/lib/vulcan/cli.rb:49: warning: Insecure world writable dir /usr/local in PATH, mode 040777
  
  done
  
  Uploading source package... done
  
  Building with: ./configure --enable-shared --disable-static --prefix=/app/vendor/llibvpx && make && make install
  
  Configuring selected codecs
  
    enabling vp8_encoder
  
    enabling vp8_decoder
  
  Configuring for target 'x86_64-linux-gcc'
  
    enabling x86_64
  
    enabling pic
  
    enabling runtime_cpu_detect
  
    enabling mmx
  
    enabling sse
  
    enabling sse2
  
    enabling sse3
  
    enabling ssse3
  
    enabling sse4_1
  
  **Neither yasm nor nasm have been found**
  
  
  
  Configuration failed. This could reflect a misconfiguration of your
  
  toolchains, improper options selected, or another problem. If you
  
  don't see any useful error messages above, the next step is to look
  
  at the configure error log file (config.err) to determine what
  
  configure was trying to do when it died.

  How can I successfully build libvpx on heroku using vulcan ?

  The instructions I've been (loosely) following are from here :

  https://gist.github.com/czivko/4392472

  And the reason I need to use libvpx is that I'm using the carrierwave-video gem in my Rails app to convert videos, and it needs libvpx to convert to webm to support video playback in Firefox.

• FFmpeg Live streaming, capture card avisynth/graphedit

  19 décembre 2013, par diegonaranjo

  I´m stuck in a problem with a test doing multicast streaming from a Viewcast Osprey 700e HD using ffmpeg.
  The thing is that I´ve to use avisynth(with graphedit) for ffmpeg recognize the card. The streaming has no ending time,
  is a live channel for IPTV.
  The script is working well, but the problem is the avisynth config, because I have to specify the countframe option,
  i think this is for the duration of the clip, but I need an infinity streaming.

  The is script is :

  ffmpeg -i espnhd.avs -rtbufsize 100000k -r 30 -c:v mpeg2video -b:v 5120k -s 1280x720 -g 100 -q:v 2 -c:a ac3 -b:a 256k -f mpegts udp ://239.192.42.61:1234

  The espnhd.avs file is :

  v=directshowsource("espnhdv.GRF", pixel_type="YUV", framecount=1000000, fps=30, audio=False, convertfps=false)
  A=directshowsource("espnhda.GRF", fps=30, framecount=1000000, video=False, convertfps=false)
  AudioDub(V, A)
  loop()

  When i run the application, work fine but the streaming ends when 1000000 frames it´s encoded...
  If i dont specify framecount, ffmpeg doesn´t start with the following error, can´t determine the duration of the clip.

  Is there any way to specify an inifinity duration on avisynth ?

  The streaming stops at 1:57hs. I took the end fo the logs :

  frame=212014 fps= 30 q=4.0 size= 6957018kB time=01:57:54.13 bitrate=8056.4kbits/s dup=0 drop=211 
  
  frame=212029 fps= 30 q=4.0 size= 6958383kB time=01:57:54.64 bitrate=8057.4kbits/s dup=0 drop=211 
  
  frame=212044 fps= 30 q=4.0 size= 6959504kB time=01:57:55.13 bitrate=8058.1kbits/s dup=0 drop=211 
  
  frame=212060 fps= 30 q=4.0 size= 6960692kB time=01:57:55.66 bitrate=8058.9kbits/s dup=0 drop=211 
  
  espnhd.avs: Not enough space
  
  [output stream 0:0 @ 02f02220] EOF on sink link output stream 0:0:default.
  
  [output stream 0:1 @ 02f10c20] EOF on sink link output stream 0:1:default.
  
  No more output streams to write to, finishing.
  
  frame=212069 fps= 30 q=4.0 Lsize= 6961519kB time=01:57:56.00 bitrate=8059.5kbits/s dup=0 drop=211 
  
  
  
  video:6196482kB audio:221125kB subtitle:0 global headers:0kB muxing overhead 8.475312%
  
  424560 frames successfully decoded, 0 decoding errors
  
  [AVIOContext @ 02f8c3e0] Statistics: 0 seeks, 4977161 writeouts
  
  [AVIOContext @ 02f032a0] Statistics: 229 bytes read, 0 seeks

  I really appreciate some help.
  Thanks.