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• 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 ?

• 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 ?

• FFmpeg image2pipe write buffer wait until done

  20 décembre 2020, par Michael Joseph Aubry

  I'm extracting frames from an external source and passing it in as a buffer to FFMPEG using image2pipe and -i -

  


  const childProcess = spawn(ffmpeg, [
  "-y",
  "-f",
  "image2pipe",
  "-i",
  "-",
  "-vcodec",
  "libx264",
  "-pix_fmt",
  "yuv420p",
  output
]);


  


  Then I have a loop that does the job.

  


  for (let i = 0; i < 250; i++) {
  // ...await
}


  


  Inside the promise

  


  // ... do the job to get buffer

childProcess.stdin.write(frame); // frame === buffer

// frame done
resolve("success!");


  


  The problem is in some videos the frames jump and is janky. This is because FFmpeg is not fully done writing to the file before moving onto the next frame.

  


  Is there a way to write a buffer to a file through FFmpeg and make sure the frame is done writing before moving on ?

  


  Some more information

  


  Here is the source file https://s3.us-west-2.amazonaws.com/storycreator.v2.uploads/ckigi4kro00160vlfjmt74afp

  


  Here is the rendered file https://s3.us-west-2.amazonaws.com/storycreator.testing/607715f0-3ab9-11eb-a139-3bb84618c6c5.mp4?t=1607585343922

  


  Here are logs

  


  2020-12-10T07:28:48.942Z    0ae0c435-54d3-416f-9d1a-8ddf595a7e83    INFO    frame=  130 fps= 16 q=-1.0 Lsize=      83kB time=00:00:05.08 bitrate= 133.6kbits/s speed=0.641x    video:80kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.928688%


  


  2020-12-10T07:28:48.942Z    0ae0c435-54d3-416f-9d1a-8ddf595a7e83    INFO    [libx264 @ 0x640d6c0] frame I:1     Avg QP:15.47  size: 68227[libx264 @ 0x640d6c0] frame P:33    Avg QP:15.07  size:   246[libx264 @ 0x640d6c0] frame B:96    Avg QP:18.75  size:    56[libx264 @ 0x640d6c0] consecutive B-frames:  1.5%  0.0%  0.0% 98.5%


  


  2020-12-10T07:28:48.943Z    0ae0c435-54d3-416f-9d1a-8ddf595a7e83    INFO    [libx264 @ 0x640d6c0] mb I  I16..4: 24.6% 60.5% 14.9%[libx264 @ 0x640d6c0] mb P  I16..4:  0.0%  0.2%  0.0%  P16..4:  0.8%  0.0%  0.0%  0.0%  0.0%    skip:98.9%[libx264 @ 0x640d6c0] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.3%  0.0%  0.0%  direct: 0.0%  skip:99.7%  L0:26.7% L1:73.3% BI: 0.0%[libx264 @ 0x640d6c0] 8x8 transform intra:62.0% inter:83.6%[libx264 @ 0x640d6c0] coded y,uvDC,uvAC intra: 49.2% 44.3% 32.1% inter: 0.0% 0.2% 0.0%[libx264 @ 0x640d6c0] i16 v,h,dc,p: 53% 38%  7%  2%[libx264 @ 0x640d6c0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 26% 24% 29%  3%  3%  3%  5%  3%  4%[libx264 @ 0x640d6c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 37% 26% 14%  3%  4%  5%  4%  4%  3%[libx264 @ 0x640d6c0] i8c dc,h,v,p: 57% 27% 13%  3%[libx264 @ 0x640d6c0] Weighted P-Frames: Y:0.0% UV:0.0%[libx264 @ 0x640d6c0] ref P L0: 95.1%  1.2%  3.1%  0.6%[libx264 @ 0x640d6c0] ref B L0: 48.1% 51.3%  0.7%[libx264 @ 0x640d6c0] ref B L1: 97.3%  2.7%[libx264 @ 0x640d6c0] kb/s:125.75


  


  2020-12-10T07:28:48.944Z    0ae0c435-54d3-416f-9d1a-8ddf595a7e83    INFO    [cache @ 0x5f57940] Statistics, cache hits:0 cache misses:3551