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• Creating thumbnails with FFmpeg

  3 janvier 2012, par Calin-Andrei Burloiu

  I am using FFmpeg to extract thumbnails from specific positions of video files.

  I found on the web two approaches to do this :

  1. With -ss (seek) parameter before -i (input) parameter :

     ffmpeg -y -ss $SEEK_POINT -i input.ogv -vcodec mjpeg -vframes 1 -an -s 120x90 -f rawvideo output.jpg

  2. With -ss (seek) parameter after -i (input) parameter :

     ffmpeg -y -i input.ogv -vcodec mjpeg -ss $SEEK_POINT -vframes 1 -an -s 120x90 -f rawvideo output.jpg

  The first method generates a bad thumbnail with gray spots, but works very fast. The error returned is [theora @ 0x8097240] vp3: first frame not a keyframe.

  The second method always works but show an error which cause the extraction to take a lot of time. This amount of time is not fixed and it depends on the seek point as I noticed. Sometimes it takes a few seconds and other times several minutes to extract a thumbnail. I get the error Buffering several frames is not supported. Please consume all available frames before adding a new one. in the following output :

  Input #0, ogg, from 'input.ogv':
  
    Duration: 00:21:52.76, start: 0.000000, bitrate: 844 kb/s
  
      Stream #0.0: Video: theora, yuv420p, 800x600 [PAR 4:3 DAR 16:9], 25 fps, 25 tbr, 25 tbn, 25 tbc
  
      Stream #0.1: Audio: vorbis, 44100 Hz, stereo, s16, 192 kb/s
  
      Metadata:
  
        ENCODER         : Lavf52.102.0
  
  Incompatible pixel format 'yuv420p' for codec 'mjpeg', auto-selecting format 'yuvj420p'                                                                         
  
  [buffer @ 0x9250840] w:800 h:600 pixfmt:yuv420p                                 
  
  [scale @ 0x92508a0] w:800 h:600 fmt:yuv420p -> w:120 h:90 fmt:yuvj420p flags:0x4
  
  Output #0, rawvideo, to 'output.jpg':
  
    Metadata:
  
      encoder         : Lavf53.2.0
  
      Stream #0.0: Video: mjpeg, yuvj420p, 120x90 [PAR 4:3 DAR 16:9], q=2-31, 200 kb/s, 90k tbn, 25 tbc
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
  Press ctrl-c to stop encoding
  
  [buffer @ 0x9250840] Buffering several frames is not supported. Please consume all available frames before adding a new one.                                    
  
  frame=    0 fps=  0 q=0.0 size=       0kB time=10000000000.00 bitrate=   0.0kbit
  
  Last message repeated 15448 times
  
  frame=    1 fps=  0 q=3.4 Lsize=       3kB time=0.04 bitrate= 598.8kbits/s    
  
  video:3kB audio:0kB global headers:0kB muxing overhead 0.000000%

  How can I extract thumbnails without any problems using FFmpeg from a custom position of a video regardless of the input format ?

• Mixing a FLV audio stream with a WAV background track, and converting to MP3 with SoX and FFmpeg

  7 septembre 2012, par tubbo

  I'm building a Flash-based recording application for a contracted web site. It streams the recorded voice (via SWF) to a Red5 server, then uses a combination of FFmpeg and SoX to compile the vocal audio with a lower-in-volume background music track. This all has to happen on-demand, that is, when a user "saves" his or her vocal recording.

  Here is an example command I will be running. Names have been changed to protect the innocent. The filenames describe their role in the final file :

  sox --combine mix -p --no-show-progress --norm "|ffmpeg -i /usr/share/red5/webapps/audiorecorder/stream/SPOKEN_VOICE.flv -t wav pipe:1" /var/www/ufiles/music/BACKGROUND_MUSIC.wav - | ffmpeg -i pipe:1 /var/www/ufiles/recordings/COMPILED_AUDIO_RECORDING.mp3

  When I run this command in the shell, this is what happens :

  $ sox --combine mix -p --no-show-progress --norm "|ffmpeg -i audioStream_1321399534128_21.flv -ar 44100 -ac 2 -t wav pipe:1" wrong.wav - | ffmpeg -i pipe:1 ~/www/trauma101.com/compiled.mp3
  
  ffmpeg version N-34884-g7575980, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on Nov 15 2011 14:06:49 with gcc 4.4.5
  
    configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libx264 --enable-x11grab --enable-libspeex
  
    libavutil    51. 25. 0 / 51. 25. 0
  
    libavcodec   53. 34. 0 / 53. 34. 0
  
    libavformat  53. 20. 0 / 53. 20. 0
  
    libavdevice  53.  4. 0 / 53.  4. 0
  
    libavfilter   2. 48. 1 /  2. 48. 1
  
    libswscale    2.  1. 0 /  2.  1. 0
  
    libpostproc  51.  2. 0 / 51.  2. 0
  
  ffmpeg version N-34884-g7575980, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on Nov 15 2011 14:06:49 with gcc 4.4.5
  
    configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libx264 --enable-x11grab --enable-libspeex
  
    libavutil    51. 25. 0 / 51. 25. 0
  
    libavcodec   53. 34. 0 / 53. 34. 0
  
    libavformat  53. 20. 0 / 53. 20. 0
  
    libavdevice  53.  4. 0 / 53.  4. 0
  
    libavfilter   2. 48. 1 /  2. 48. 1
  
    libswscale    2.  1. 0 /  2.  1. 0
  
    libpostproc  51.  2. 0 / 51.  2. 0
  
  [libspeex @ 0x1e36b20] Missing Speex header, assuming defaults.
  
  Input #0, flv, from 'audioStream_1321399534128_21.flv':
  
    Metadata:
  
      novideocodec    : 0
  
      server          : Red5 Server 1.0.0 RC2 Rev: 4295
  
      creationdate    : Tue Nov 15 15:25:41 PST 2011
  
      canSeekToEnd    : true
  
    Duration: 00:00:06.77, start: 0.000000, bitrate: 43 kb/s
  
      Stream #0:0: Audio: speex, 16000 Hz, 1 channels, s16
  
  Invalid duration specification for t: wav
  
  sox FAIL formats: can't open input pipe `|ffmpeg -i audioStream_1321399534128_21.flv -ar 44100 -ac 2 -t wav pipe:1': premature EOF

  I think the issue is stemming from the conversion from FLV to WAV in FFmpeg, and since it's being piped in it causes the whole process to fail. I always get that duration warning, but when FFmpeg outputs to a .wav file and the SoX command is run separately, I can still get a WAV from SoX and convert that to MP3 manually. I'd like to do all this in one line, piping the data between applications.

  What do I do ?

• FFmpeg / Create video / Add caption (timestamp) of each jpg file to generate mp4

  17 août 2012, par low

  I've got some pictures, as screenshot-1.jpg, ..., screenshot-345.jpg, cycle of automatic capture from my computer (cycle of 30 seconds). I use FFmpeg to generate a video mp4 format, but, I want to add on the video the timestamp of each jpg file.

  This is my command line of FFmpeg :

  ffmpeg.exe -f image2 -r 4 -i screenshot-%0d.jpg -b 512000 -s 3840x1200 -sameq video.mp4

  In this case, I can show the date/time during de video play.

  Thanks.
  Low