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• FFMpeg is writing a matplotlib animation with diminishing quality

  3 mars 2017, par Bryan Stafford

  I am trying to create a bunch of animations that follow the paths National Hockey League teams travel during the current season. Currently, my animation looks like this.

  As you can see, the animation begins decently sharp but within 2 seconds the quality bottoms out and everything is grainy.

  The relevant code is this :

  ani = animation.FuncAnimation(fig, update, frames=len(all_x + 20), 
  
                                interval=75, repeat=False)
  
  filepath =  map_team + '.mp4'
  
  ani.save(filepath, writer='ffmpeg', fps=30)
  
  plt.tight_layout()
  
  plt.show()

  I have chosen FFMpeg as my writer because I hope to put about 30 graphics online and the MP4 format keeps each file around 1.5MB. If there’s a way to keep the graphics sharp, with low file sizes, and able to be uploaded onto Imgur, I would love to do that with my project.

  Thanks.

• FFmpeg per stream metadata change with more audio streams

  22 août 2014, par tomasb

  I’m trying to change audio stream title for a movie which was originally with DTS sound. I have added AC3 version using -map parameter, want to keep both. My problem is that the AC3 audio stream bears DTS stream metadata. I am using FFmpeg 1.2

  Tried :

  ffmpeg -i movie.mkv -c copy \
  
  -metadata:s:1 title="AC3 5.1 640 kb/s" -y movie.temp.mkv 

  this partially works, but output file contains only 1 of each stream type, i.e. 1 video, 1 audio and 1 subtitle stream. When i try to get all the streams contained in my mkv like this :

  ffmpeg -i movie.mkv -map 0 \
  
  -metadata:s:1 title="AC3 5.1 640 kb/s" -y movie.temp.mkv 

  i am getting strange output :

  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 -> libx264)
  
    Stream #0:1 -> #0:1 (ac3 -> libvorbis)
  
    Stream #0:2 -> #0:2 (subrip -> ass)
  
    Stream #0:3 -> #0:3 (dca -> libvorbis)
  
    Stream #0:4 -> #0:4 (ac3 -> libvorbis)
  
    Stream #0:5 -> #0:5 (subrip -> ass)
  
  Press [q] to stop, [?] for help
  
  [libvorbis @ 0x12e5a40] Queue input is backward in time
  
      Last message repeated 19 times
  
  Queue input is backward in time      20kB time=00:00:01.05 bitrate= 156.8kbits/s    
  
  [libvorbis @ 0x12e5a40] Queue input is backward in time
  
      Last message repeated 17 times
  
  Queue input is backward in time      20kB time=00:00:01.99 bitrate=  83.0kbits/s    
  
  [libvorbis @ 0x12e5a40] Queue input is backward in time
  
      Last message repeated 5 times
  
  Queue input is backward in time=      20kB time=00:00:02.38 bitrate=  69.5kbits/s    
  
  [libvorbis @ 0x12e5a40] Queue input is backward in time
  
      Last message repeated 6 times
  
  Queue input is backward in time=      20kB time=00:00:02.87 bitrate=  57.5kbits/s    
  
  [libvorbis @ 0x12e5a40] Queue input is backward in time
  
  ...

  I have found information that FFmpeg’s attributes under linux are inconsistent when manipulating per stream metadata and doesn’t work as expected so I am looking for some alternative way how to proceed. (preferably with ffmpeg)

  Thanks for any help.

• Air and ffmpeg with NativeProcess

  16 mai 2013, par Pierre

  I´trying to create an Air application that can generate a movie file via ffmpeg. I´m using NativeProcess and it all works fine if (and only if) I add an ffmpeg that is compiled on my computer to the native installer. Whenever I try to use a precompiled build the process fails like this :

  NSTask : Task create for path 'mypathto/ffmpeg' failed : 22, "Invalid argument". Terminating temporary process.

  If I was the only user I wouldn´t have a problem. But I want other people to use my application so I really need to bundle the ffmpeg with my native installer.

  I have tried several different builds with the same result. Here is the argument string before I put in the process arguments Vector : "-y -f image2 -i seq%04d.png movie.mpg".

  Please help !