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• Giving Thanks For VP8

  25 novembre 2010, par Multimedia Mike — VP8

  It’s the Thanksgiving holiday here in the United States. I guess that’s as good a reason as any to release a first cut of my VP8 encoder. In order to remind people that they shouldn’t expect phenomenal quality from it — and to discourage inexperienced people from trying to create useful videos with it — I have hardcoded the quantizers to their maximum settings. For those not skilled in the art, this is the setting that yields maximum compression and worst quality. When compressing the Big Buck Bunny logo image, the resulting file is only 2839 bytes but observe the reconstructed quality :

  
  
  It really just looks like a particularly stormy day in the forest.
  

  First VP8 File From An Independent Encoder
  I found a happy medium on the quantizer scale and encoded the first 30 seconds of Big Buck Bunny for your inspection. I guess this makes it the first VP8/WebM file from an independent encoder (using FFmpeg’s Matroska muxer as well).

  Download : bbb-360p-30sec-q40.webm ( 13 MBytes)

  I think the quality makes it look like it was digitized from an old VHS tape.

  For fun, here’s the version with the quantizer cranked to the max : bbb-360p-30sec-q127.webm ( 1.3 MBytes)

  Aside : I was going to encapsulate the video in this post using a bare HTML5 <video> tag for the benefit of the small browsing population who could view that (indeed, it works fine in Chrome). But that would be insane due to the fact that supporting browsers preload the video with no easy (read : without the help of JavaScript) method for overriding this unacceptable default.

  The Code
  I’m still trying to get over my fear of git. To that end, I have posted the code on Github :

  https://github.com/multimediamike/ffvp8enc

  I still don’t like you, git. But I’m sure we’ll find some way to make this work.

  Other required code changes in the basic FFmpeg tree :

  • Of course, copy vp8enc.c into libavcodec/
  • In libavcodec/allcodecs.c, ’REGISTER_DECODER (VP8, vp8);’ turns into ’REGISTER_ENCDEC (VP8, vp8);’
  • Add ’OBJS-$(CONFIG_VP8_ENCODER) += vp8enc.o’ to libavcodec/Makefile

  Further Work
  About the limitations and work yet to do :

  • it’s still intra-only, no interframes (which is where a lot of compression occurs)
  • no rate control or distortion optimization, obviously
  • no intra 4x4 coding (that’s close to working but didn’t my little T-day deadline)
  • no quantization control ; this should really be hooked up to the FFmpeg command line but I’m not sure how
  • encoder writes into a static-sized, 1/2 MB memory buffer ; this can overflow
  • code is a mess (what did you expect at this stage of the game ?)
  • lots and lots of other things, surely

• `ffmpet -f concat` don't work when all input streams appear to have the same spec

  9 mars 2023, par Roy

  My ffmpeg command :

  &#xA;

  ffmpeg -safe 0 -f concat -i list.txt -c copy out.mp4


  &#xA;

  My 1st input file :

  &#xA;

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'D:\Applications\ffmpeg_6.0_full\a.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf60.3.100
  Duration: 00:00:04.97, start: 0.000000, bitrate: 40 kb/s
  Stream #0:0[0x1](und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 2 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 27 kb/s, 30 fps, 30 tbr, 30k tbn (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : Lavc60.3.100 libx264


  &#xA;

  My 2nd input file :

  &#xA;

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'D:\Applications\ffmpeg_6.0_full\b.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp41isom
    creation_time   : 2023-03-08T06:47:13.000000Z
    artist          : Microsoft Game DVR
    title           : PUBG: BATTLEGROUNDS
  Duration: 00:10:00.16, start: 0.000000, bitrate: 20885 kb/s
  Stream #0:0[0x1](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 20739 kb/s, 30 fps, 30 tbr, 30k tbn (default)
    Metadata:
      creation_time   : 2023-03-08T06:47:13.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : AVC Coding
  Stream #0:1[0x2](und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 131 kb/s (default)
    Metadata:
      creation_time   : 2023-03-08T06:47:13.000000Z
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]


  &#xA;

  The above command outputs some warning signals :

  &#xA;

  [mov,mp4,m4a,3gp,3g2,mj2 @ 0000025239902d40] Auto-inserting h264_mp4toannexb bitstream filter
[mp4 @ 00000252396fe5c0] Non-monotonous DTS in output stream 0:1; previous: 218112, current: 150024; changing to 218113. This may result in incorrect timestamps in the output file.
...
a lot of them
...
frame=25992 fps=21754 q=-1.0 Lsize= 1519621kB time=00:14:49.39 bitrate=13996.8kbits/s speed= 744x
video:9649kB audio:1519216kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown


  &#xA;

  The resultant video can play the first part of the video correctly, then the video players either skips directly to the end of the video (MPC-HC), or don't render anything at all while timer passes as normal (VLC).

  &#xA;

  My impression of the concat is that it requires all videos to have the same spec, which I think my input achieved (all the "Steam #0:0", etc, line matches). I only see the following difference, which I assumed that should be okay :

  &#xA;

  &#xA;
  1. Metadata are different both for the whole input (e.g. "major_brand") and for each stream (e.g. "encoder"). I assumed that metadata won't affect the processing.

  &#xA;

  2. The order of video/audio streams are different in the two inputs : the 1st input file has audio then video ; the 2nd input file has video then audio. I assumed that ffmpeg knows the difference and won't concat a video stream to an audio stream.

  &#xA;

  &#xA;

  The full output of the command can be found in this pastebin : https://pastebin.com/Z5q97Uyg

  &#xA;

• `ffmpeg -f concat` don't work when all input streams appear to have the same spec

  2 octobre 2024, par Roy

  My ffmpeg command :

  &#xA;

  ffmpeg -safe 0 -f concat -i list.txt -c copy out.mp4


  &#xA;

  My 1st input file :

  &#xA;

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'D:\Applications\ffmpeg_6.0_full\a.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf60.3.100
  Duration: 00:00:04.97, start: 0.000000, bitrate: 40 kb/s
  Stream #0:0[0x1](und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 2 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 27 kb/s, 30 fps, 30 tbr, 30k tbn (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : Lavc60.3.100 libx264


  &#xA;

  My 2nd input file :

  &#xA;

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'D:\Applications\ffmpeg_6.0_full\b.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp41isom
    creation_time   : 2023-03-08T06:47:13.000000Z
    artist          : Microsoft Game DVR
    title           : PUBG: BATTLEGROUNDS
  Duration: 00:10:00.16, start: 0.000000, bitrate: 20885 kb/s
  Stream #0:0[0x1](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 20739 kb/s, 30 fps, 30 tbr, 30k tbn (default)
    Metadata:
      creation_time   : 2023-03-08T06:47:13.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : AVC Coding
  Stream #0:1[0x2](und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 131 kb/s (default)
    Metadata:
      creation_time   : 2023-03-08T06:47:13.000000Z
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]


  &#xA;

  The above command outputs some warning signals :

  &#xA;

  [mov,mp4,m4a,3gp,3g2,mj2 @ 0000025239902d40] Auto-inserting h264_mp4toannexb bitstream filter
[mp4 @ 00000252396fe5c0] Non-monotonous DTS in output stream 0:1; previous: 218112, current: 150024; changing to 218113. This may result in incorrect timestamps in the output file.
...
a lot of them
...
frame=25992 fps=21754 q=-1.0 Lsize= 1519621kB time=00:14:49.39 bitrate=13996.8kbits/s speed= 744x
video:9649kB audio:1519216kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown


  &#xA;

  The resultant video can play the first part of the video correctly, then the video players either skips directly to the end of the video (MPC-HC), or don't render anything at all while timer passes as normal (VLC).

  &#xA;

  My impression of the concat is that it requires all videos to have the same spec, which I think my input achieved (all the "Steam #0:0", etc, line matches). I only see the following difference, which I assumed that should be okay :

  &#xA;

  &#xA;
  1. Metadata are different both for the whole input (e.g. "major_brand") and for each stream (e.g. "encoder"). I assumed that metadata won't affect the processing.

  &#xA;

  2. The order of video/audio streams are different in the two inputs : the 1st input file has audio then video ; the 2nd input file has video then audio. I assumed that ffmpeg knows the difference and won't concat a video stream to an audio stream.

  &#xA;

  &#xA;

  The full output of the command can be found in this pastebin : https://pastebin.com/Z5q97Uyg

  &#xA;