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• ffmpeg : avfilter's anull says "Rematrix is needed between stereo and 0 channels but there is not enough information to do it"

  12 juillet 2017, par kuanyui

  I’m trying to write a transcoder according to FFMpeg’s official example with ffmpeg 3.2.4 (official prebuild Win32), and try to transcode a video with stereo audio stream source (from avformat’s dshow).

  In the example code, which passes anull into avfilter_graph_parse_ptr() for audio stream, and "time_base=1/44100:sample_rate=44100:sample_fmt=s16:channels=2:channel_layout=0x3" is passed into avfilter_graph_create_filter(), occurs error in the following avfilter_graph_config() :

  [auto-inserted scaler 0 @ 32f77600] w:iw h:ih flags:'bilinear' interl:0
  
  [Parsed_null_0 @ 2e9d79a0] auto-inserting filter 'auto-inserted scaler 0' between the filter 'in' and the filter 'Parsed_null_0'
  
  [swscaler @ 3331bfe0] deprecated pixel format used, make sure you did set range correctly
  
  [auto-inserted scaler 0 @ 32f77600] w:1920 h:1080 fmt:yuvj422p sar:1/1 -> w:1920 h:1080 fmt:yuv420p sar:1/1 flags:0x2
  
  [libmp3lame @ 2e90a360] Channel layout not specified
  
  [in @ 3866e8a0] tb:1/44100 samplefmt:s16 samplerate:44100 chlayout:0x3
  
  [Parsed_anull_0 @ 330e8820] auto-inserting filter 'auto-inserted resampler 0' between the filter 'in' and the filter 'Parsed_anull_0'
  
  [auto-inserted resampler 0 @ 330e8dc0] [SWR @ 3809b620] Rematrix is needed between stereo and 0 channels but there is not enough information to do it
  
  [auto-inserted resampler 0 @ 330e8dc0] Failed to configure output pad on auto-inserted resampler 0

  I’ve googled for days but didn’t find any clue for it. Doesn’t what anull do is only "Pass the audio source unchanged to the output", why libav want to resample stereo to 0 channel ? What’s going wrong ?

• Shaking/trembling in video slideshow generated by frames from an image

  18 mai 2017, par raziel

  I have a PHP program which is used to generate a video slideshow from the series of images. Basically, I just need to smoothly ‘move’ from one image area to the another one according to the specified top/left coordinates and width/height area of the image. In order to do smooth movement, I use easing functions during the coordinates calculations for the each of video frame. I make an jpeg image frame based on these calculations using PHP’s Imagick library, then I combine all the generated frames into a single video using ffmpeg command.

  <?php
  
  const TEMP_FRAMES_DIR = __DIR__;
  
  const VIDEO_WIDTH = 1080;
  
  const VIDEO_HEIGHT = 720;
  
  const FPS = 30;
  
  const MOVEMENT_DURATION_SECONDS = 3;
  
  
  
  const IMAGE_PATH = __DIR__ . '/test_image.png';
  
  
  
  $start_coords = [
  
      'x' => 100,
  
      'y' => 100,
  
      'width'  => 480,
  
      'height' => 270
  
  ];
  
  $end_coords = [
  
      'x' => 400,
  
      'y' => 200,
  
      'width'  => 480,
  
      'height' => 270
  
  ];
  
  
  
  $timeline = make_timeline($start_coords, $end_coords);
  
  render_frames(IMAGE_PATH, $timeline);
  
  render_video_from_frames();
  
  
  
  function make_timeline($start_coords, $end_coords) {
  
      $timeline = [];
  
  
  
      $total_frames = MOVEMENT_DURATION_SECONDS * FPS;
  
  
  
      $x_change      = $end_coords['x']      - $start_coords['y'];
  
      $y_change      = $end_coords['y']      - $start_coords['y'];
  
      $width_change  = $end_coords['width']  - $start_coords['width'];
  
      $height_change = $end_coords['height'] - $start_coords['height'];
  
  
  
      for ($i = 0; $i < $total_frames; $i++) {
  
          $timeline[$i] = [
  
              'x'      => easingOutExpo($i, $start_coords['x'], $x_change, $total_frames),
  
              'y'      => easingOutExpo($i, $start_coords['y'], $y_change, $total_frames),
  
              'width'  => easingOutExpo($i, $start_coords['width'], $width_change, $total_frames),
  
              'height' => easingOutExpo($i, $start_coords['height'], $height_change, $total_frames)
  
          ];
  
      }
  
      return $timeline;
  
  }
  
  
  
  function render_frames($image_path, $timeline) {
  
      $image = new Imagick($image_path);
  
      //remove frames from the previous render
  
      array_map('unlink', glob( TEMP_FRAMES_DIR . "/frame*" ));
  
  
  
      foreach ($timeline as $frame_number => $frame) {
  
          $frame_img = clone $image;
  
          $frame_img->cropImage($frame["width"],$frame["height"], $frame["x"],$frame["y"]);
  
          $frame_img->resizeImage(VIDEO_WIDTH, VIDEO_HEIGHT, imagick::FILTER_LANCZOS, 0.9);
  
          $frame_img->writeImage(TEMP_FRAMES_DIR. "/frame$frame_number.jpg");
  
      }
  
  }
  
  
  
  function render_video_from_frames() {
  
      $fps = FPS;
  
      $frames_dir = TEMP_FRAMES_DIR;
  
      $SEP = DIRECTORY_SEPARATOR;
  
  
  
      $video_file = $frames_dir. $SEP . 'video.mp4';
  
  
  
      if (file_exists($video_file)) unlink($video_file);
  
  
  
      system("ffmpeg -framerate $fps -i $frames_dir{$SEP}frame%01d.jpg $video_file");
  
  }
  
  
  
  function easingOutExpo($t, $b, $c, $d) {
  
      return $c * ( -pow( 2, -10 * $t/$d ) + 1 ) + $b;
  
  }

  The problem is that I have annoying shaking/trembling when I need to move at a low speed (like at the end of easing out expo function).
  Here you can get the test video with the problem, the test image which was used and the PHP script :
  https://drive.google.com/drive/u/1/folders/0B9FOrF6IlWaGeHJCS1h6djhVZ28

  You can see this shaking starting from the middle of the test video ( 1.5 sec).

  How can I avoid shaking in such kind of situations ? Thanks in advance !

• FFMPEG being killed when processing H264 video

  4 mai 2017, par Stuart Clarke

  I have a program that when given a video (video.mp4), extracts the audio, a thumbnail image and the video into separate files, adds some background music to the audio file to create a new file (combined.mp3), increases the resolution of the video to 1080p and saves to a new file (videoHD.mp4), adds intro and credits to the start and end (already in 1080p) and saves that to a new file (merged.mp4) and finally combines the processed video and audio into an output file (videoExt.mp4). I’m using ffmpeg through python and subprocess.call to do all this but the raw ffmpeg commands are as follows.

  ffmpeg -y -i video.mp4 -acodec mp3 audioTrack.mp3
  
  
  
  ffmpeg -y -ss 00:00:00 -i video.mp4 -vframes 1 -q:v 2 thumb.jpg
  
  
  
  ffmpeg -y -i video.mp4 -an videoTrack.mp4
  
  
  
  ffmpeg -y -i audioTrack.mp3 -i musicTrack.mp3 -filter_complex amerge -c:a libmp3lame -q:a 4 combined.mp3
  
  
  
  ffmpeg -y -i videoTrack.mp4 -vf 'scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:x=(1920-iw)/2:y=(1080-ih)/2:color=black' videoHD.mp4
  
  
  
  ffmpeg -y -f concat -i vids.ini -an merged.mp4
  
  
  
  ffmpeg -y -i merged.mp4 -i combined.mp3 -strict -2 -shortest videoExt.mp4

  Between extracting the audio and combining with the music I add a silent period matching the intro length to the beginning for the audio and lower the volume of the music for the duration of the video section and crop the music to the length of the combined intro, video and credits. This is all done with AudioSegment and works well.

  My problem is that the ffmpeg process keeps being killed. It happens in various places at various times, but always when processing the video at 1080p. I’m sure it has something to do with the H264 codec but when I use mpeg4 the quality is terrible. The videos are always less than a minute (Instagram videos) and at most 25Mb, I’m using a VPS with Ubuntu Server 15.04 installed, it should be able to handle this surely. If not is there a way around it, processing the video in parts ?

  Here is an example of the error but as I said, it can happen in various places and sometimes will complete for one command but I have never had it complete for all.

  # ffmpeg -y -f concat -i vids.ini -an merged.mp4
  
  
  
  ffmpeg version 2.5.10-0ubuntu0.15.04.1 Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 4.9.2 (Ubuntu 4.9.2-10ubuntu13)
  
    configuration: --prefix=/usr --extra-version=0ubuntu0.15.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --shlibdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --enable-shared --disable-stripping --enable-avresample --enable-avisynth --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libshine --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libwavpack --enable-libwebp --enable-libxvid --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzvbi --enable-libzmq --enable-frei0r --enable-libvpx --enable-libx264 --enable-libsoxr --enable-gnutls --enable-openal --enable-libopencv --enable-librtmp --enable-libx265
  
    libavutil      54. 15.100 / 54. 15.100
  
    libavcodec     56. 13.100 / 56. 13.100
  
    libavformat    56. 15.102 / 56. 15.102
  
    libavdevice    56.  3.100 / 56.  3.100
  
    libavfilter     5.  2.103 /  5.  2.103
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Input #0, concat, from 'vids.ini':
  
    Duration: N/A, start: 0.000000, bitrate: 2999 kb/s
  
      Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 2996 kb/s, 29.97 fps, 29.97 tbr, 11988 tbn, 59.94 tbc
  
      Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 2 kb/s
  
  [libx264 @ 0x134fd00] using SAR=1/1
  
  [libx264 @ 0x134fd00] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
  
  [libx264 @ 0x134fd00] profile High, level 4.0
  
  [libx264 @ 0x134fd00] 264 - core 142 r2495 6a301b6 - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  Output #0, mp4, to 'merged.mp4':
  
    Metadata:
  
      encoder         : Lavf56.15.102
  
      Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=-1--1, 29.97 fps, 11988 tbn, 29.97 tbc
  
      Metadata:
  
        encoder         : Lavc56.13.100 libx264
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  
  Press [q] to stop, [?] for help
  
  frame=   13 fps=0.0 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A dup=1 dro
  
  frame=   28 fps= 27 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A dup=1 dro
  
  frame=   46 fps= 21 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A dup=1 dro
  
  frame=   51 fps= 16 q=29.0 size=     120kB time=00:00:00.-3 bitrate=N/A dup=1 dr
  
  frame=   55 fps= 15 q=29.0 size=     154kB time=00:00:00.10 bitrate=12574.5kbits
  
  frame=   60 fps= 14 q=29.0 size=     195kB time=00:00:00.26 bitrate=5981.0kbits/
  
  frame=   65 fps= 13 q=29.0 size=     254kB time=00:00:00.43 bitrate=4797.0kbits/
  
  frame=   69 fps= 12 q=29.0 size=     287kB time=00:00:00.56 bitrate=4142.1kbits/
  
  frame=   73 fps= 12 q=29.0 size=     375kB time=00:00:00.70 bitrate=4384.2kbits/
  
  frame=   76 fps= 11 q=29.0 size=     418kB time=00:00:00.80 bitrate=4278.4kbits/
  
  frame=   81 fps= 11 q=29.0 size=     441kB time=00:00:00.96 bitrate=3732.4kbits/
  
  frame=   85 fps= 10 q=29.0 size=     472kB time=00:00:01.10 bitrate=3511.0kbits/
  
  Killed1 drop=0 

  Any ideas or if anyone knows a better way to this please let me know.

  Cheers,

  Stu