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• Compressing videos from a smartphone

  21 septembre 2019, par fejesjoco

  I have a Nexus 6p with the stock camera. It’s set to record at 1080p, 30fps. Here’s a 5 second sample (11 MB).

  Videos from this phone come out at about 17 Mbps on average. I tried to compress it with ffmpeg with -c:v libx264 -crf 23 -preset veryslow, the result comes out at about 5.5 MB, which is about 9 Mbps.

  I think this bitrate is a bit too much. When I look at torrent file listings, I can see high quality videos at 3 GB in size on average, and if such a movie is 90 minutes long on average, that is about 4-5 Mbps which sounds okay.

  I’m wondering, why the big difference ? I can notice that my video is noisy/grainy (which is expected from a phone), and that might reduce compressibility. I tried a few ffmpeg filters, like hqdn3d and atadenoise, but the noise mostly remained (maybe I didn’t play with it enough). Then I figured, the video is also shaky (which is also expected), and that might reduce compressibility too (and even makes temporal noise filtering less effective). I tried to stabilize it with the deshake filter, but that didn’t help either.

  I know I could just limit the bandwidth to whatever I like, but there must be a reason why ffmpeg thinks it needs a high bandwidth to maintain a certain quality, and a lower bandwidth would just decrease the quality.

  Why do these videos have such a high bitrate ? What’s the best way to compress them more while keeping or even increasing their quality ?

• Compressing videos from a smartphone

  9 novembre 2016, par fejesjoco

  I have a Nexus 6p with the stock camera. It’s set to record at 1080p, 30fps. Here’s a 5 second sample (11 MB).

  Videos from this phone come out at about 17 Mbps on average. I tried to compress it with ffmpeg with -c:v libx264 -crf 23 -preset veryslow, the result comes out at about 5.5 MB, which is about 9 Mbps.

  I think this bitrate is a bit too much. When I look at torrent file listings, I can see high quality videos at 3 GB in size on average, and if such a movie is 90 minutes long on average, that is about 4-5 Mbps which sounds okay.

  I’m wondering, why the big difference ? I can notice that my video is noisy/grainy (which is expected from a phone), and that might reduce compressibility. I tried a few ffmpeg filters, like hqdn3d and atadenoise, but the noise mostly remained (maybe I didn’t play with it enough). Then I figured, the video is also shaky (which is also expected), and that might reduce compressibility too (and even makes temporal noise filtering less effective). I tried to stabilize it with the deshake filter, but that didn’t help either.

  I know I could just limit the bandwidth to whatever I like, but there must be a reason why ffmpeg thinks it needs a high bandwidth to maintain a certain quality, and a lower bandwidth would just decrease the quality.

  Why do these videos have such a high bitrate ? What’s the best way to compress them more while keeping or even increasing their quality ?

• ffmpeg : unable to cut avi movie

  10 mars 2016, par ird

  I am using ffmpeg to cut video file :

  ffmpeg -<inputfile> -ss 00:00:00 -t 00:00:30 <outputfile>
  
  </outputfile></inputfile>

  It’s OK for different file formats exclude *.avi format. For avi movies ffmpeg shows that video is truncated, but output file contains full video (without truncating).
  Does anybody know possible ways for problem troubleshooting ?

  Here converting command output for avi file :

  FFmpeg version SVN-r26402, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on Feb  1 2011 02:54:36 with gcc 4.4.5
  
    configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
  
    libavutil     50.36. 0 / 50.36. 0
  
    libavcore      0.16. 1 /  0.16. 1
  
    libavcodec    52.108. 0 / 52.108. 0
  
    libavformat   52.93. 0 / 52.93. 0
  
    libavdevice   52. 2. 3 / 52. 2. 3
  
    libavfilter    1.74. 0 /  1.74. 0
  
    libswscale     0.12. 0 /  0.12. 0
  
    libpostproc   51. 2. 0 / 51. 2. 0
  
  [mpeg4 @ 0x91e7e10] Invalid and inefficient vfw-avi packed B frames detected
  
  
  
  Seems stream 0 codec frame rate differs from container frame rate: 30000.00 (30000/1) -> 25.00 (25/1)
  
  Input #0, avi, from '/home/mightymeeting/Videos/tam-19.avi':
  
    Duration: 00:04:43.32, start: 0.000000, bitrate: 564 kb/s
  
      Stream #0.0: Video: mpeg4, yuv420p, 352x208 [PAR 1:1 DAR 22:13], 25 fps, 25 tbr, 25 tbn, 30k tbc
  
      Stream #0.1: Audio: mp3, 32000 Hz, 2 channels, s16, 80 kb/s
  
  [buffer @ 0x91e6ed0] w:352 h:208 pixfmt:yuv420p
  
  Output #0, avi, to 'out.avi':
  
    Metadata:
  
      ISFT            : Lavf52.93.0
  
      Stream #0.0: Video: mpeg4, yuv420p, 352x208 [PAR 1:1 DAR 22:13], q=2-31, 200 kb/s, 25 tbn, 25 tbc
  
      Stream #0.1: Audio: mp2, 32000 Hz, 2 channels, s16, 64 kb/s
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
    Stream #0.1 -> #0.1
  
  Press [q] to stop encoding
  
  [mpeg4 @ 0x91e7e10] Invalid and inefficient vfw-avi packed B frames detected
  
  frame= 7082 fps=999 q=2.0 Lsize=    7513kB time=30.02 bitrate=2049.8kbits/s dup=0 drop=1    
  
  video:7079kB audio:235kB global headers:0kB muxing overhead 2.718192%