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• Prevent ffmpeg from changing the intensity of colors while downscaling the resolution of the video

  29 août 2022, par dravit

  I have a use case where I need to downscale a 716x1280 mp4 video to 358x640 (half of the original). Command that I used is

  


  ffmpeg -i ./input.mp4 -vf "scale=640:640:force_original_aspect_ratio=decrease,pad=ceil(iw/2)*2:ceil(ih/2)*2" ./output.mp4


  


  Out of 10 sample videos, 2 of the them suffered impact on colors. Below I have attached a comparison from the one which was impacted the most.

  


  

  


  NOTE : The one on the right is a frame from the original video and the frame on the left is the one from the processed (down scaled) video. Notice the colors red and green in the image (even the skin color and hair color were changed).

  


  What I am looking for is

  


  

  • Is there any way I can prevent changes like these happening ? Probably some flag on saturation, brightness, contrast or any other parameter.

  


  • I am assuming that ffmpeg uses some default settings while downscaling a video. What made ffmpeg change colors only for these two videos ? If it made similar changes for the rest of the videos as well, how to predict this behaviour before hand ?

  


  


  EDIT :

  


  What I already have Tried ?

  


  

  • -crf with values 0 and 18.

  


  • -preset veryslow as mentioned here

  


  


  None helped

  


  Mediainfo input V/S output

  


  





  


  


  


  


  


  



  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  param	input	output
  color range	Limited	NA (attribute not in description)
  color primaries	BT.2020	NA (attribute not in description)
  transfer characteristics	HLG	NA (attribute not in description)
  matrix coefficients	BT.2020 non-constant	NA (attribute not in description)
  bit deapth	8	8

  


  


  Logs of the ffmpeg command

  


  ffmpeg -i ./input.mp4 -vf "scale=640:640:force_original_aspect_ratio=decrease,pad=ceil(iw/2)*2:ceil(ih/2)*2" -movflags +faststart ./output.mp4
ffmpeg version 4.3.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with Apple clang version 12.0.0 (clang-1200.0.32.28)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.1_9 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from './input.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
  Duration: 00:00:30.05, start: 0.000000, bitrate: 10366 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt2020nc/bt2020/arib-std-b67), 716x1280, 10116 kb/s, 30 fps, 30 tbr, 19200 tbn, 38400 tbc (default)
    Metadata:
      handler_name    : Core Media Video
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 245 kb/s (default)
    Metadata:
      handler_name    : Core Media Audio
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 0x7faab4808800] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7faab4808800] profile High, level 3.0, 4:2:0, 8-bit
[libx264 @ 0x7faab4808800] 264 - core 161 r3027 4121277 - H.264/MPEG-4 AVC codec - Copyleft 2003-2020 - 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=12 lookahead_threads=2 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 './output.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
    Stream #0:0(und): Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 358x640, q=-1--1, 30 fps, 15360 tbn, 30 tbc (default)
    Metadata:
      handler_name    : Core Media Video
      encoder         : Lavc58.91.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : Core Media Audio
      encoder         : Lavc58.91.100 aac
[mp4 @ 0x7faab5808800] Starting second pass: moving the moov atom to the beginning of the file
frame=  901 fps=210 q=-1.0 Lsize=    3438kB time=00:00:30.02 bitrate= 938.0kbits/s speed=7.01x
video:2933kB audio:472kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.974633%
[libx264 @ 0x7faab4808800] frame I:6     Avg QP:22.60  size: 20769
[libx264 @ 0x7faab4808800] frame P:228   Avg QP:24.84  size:  7657
[libx264 @ 0x7faab4808800] frame B:667   Avg QP:27.59  size:  1697
[libx264 @ 0x7faab4808800] consecutive B-frames:  0.9%  0.9%  1.0% 97.2%
[libx264 @ 0x7faab4808800] mb I  I16..4:  9.5% 64.6% 26.0%
[libx264 @ 0x7faab4808800] mb P  I16..4:  2.5% 12.2%  2.5%  P16..4: 37.2% 20.6% 11.2%  0.0%  0.0%    skip:13.7%
[libx264 @ 0x7faab4808800] mb B  I16..4:  0.4%  2.1%  0.2%  B16..8: 42.2%  7.1%  1.2%  direct: 1.8%  skip:44.9%  L0:39.4% L1:52.8% BI: 7.8%
[libx264 @ 0x7faab4808800] 8x8 transform intra:72.2% inter:74.2%
[libx264 @ 0x7faab4808800] coded y,uvDC,uvAC intra: 61.8% 67.2% 20.2% inter: 16.7% 13.9% 1.3%
[libx264 @ 0x7faab4808800] i16 v,h,dc,p: 24% 19%  7% 50%
[libx264 @ 0x7faab4808800] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 21% 16% 15%  6%  9% 11%  7% 10%  6%
[libx264 @ 0x7faab4808800] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 16% 13%  7%  9% 10%  7%  9%  4%
[libx264 @ 0x7faab4808800] i8c dc,h,v,p: 53% 16% 26%  5%
[libx264 @ 0x7faab4808800] Weighted P-Frames: Y:3.9% UV:1.8%
[libx264 @ 0x7faab4808800] ref P L0: 57.8% 19.5% 14.8%  7.8%  0.1%
[libx264 @ 0x7faab4808800] ref B L0: 90.7%  7.2%  2.1%
[libx264 @ 0x7faab4808800] ref B L1: 95.3%  4.7%
[libx264 @ 0x7faab4808800] kb/s:799.80
[aac @ 0x7faab2036a00] Qavg: 189.523


  


• http: restructure http_connect error handling path

  21 mars 2014, par wm4

  http: restructure http_connect error handling path
  The authstr memory allocations make it annoying to error in the middle
  
  of the header setup code, so apply the usual C error handling idiom to
  
  make it easier to error at any point.
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavformat/http.c

• Implementing a chained overlay filter with the Libavfilter library in Android NDK

  14 mars 2014, par gookman

  I am trying to use the overlay filter with multiple input sources, for an Android app. Basically, I want to overlay multiple video sources on top of a static image.
  I have looked at the sample that comes with ffmpeg and implemented my code based on that, but things don't seem to be working as expected.

  In the ffmpeg filtering sample there seems to be a single video input. I have to handle multiple video inputs and I am not sure that my solution is the correct one. I have tried to find other examples, but looks like this is the only one.

  Here is my code :

  AVFilterContext **inputContexts;
  
  AVFilterContext *outputContext;
  
  AVFilterGraph *graph;
  
  
  
  int initFilters(AVFrame *bgFrame, int inputCount, AVCodecContext **codecContexts, char *filters)
  
  {
  
      int i;
  
      int returnCode;
  
      char args[512];
  
      char name[9];
  
      AVFilterInOut **graphInputs = NULL;
  
      AVFilterInOut *graphOutput = NULL;
  
  
  
      AVFilter *bufferSrc  = avfilter_get_by_name("buffer");
  
      AVFilter *bufferSink = avfilter_get_by_name("buffersink");
  
  
  
      graph = avfilter_graph_alloc();
  
      if(graph == NULL)
  
          return -1;
  
  
  
      //allocate inputs
  
      graphInputs = av_calloc(inputCount + 1, sizeof(AVFilterInOut *));
  
      for(i = 0; i <= inputCount; i++)
  
      {
  
          graphInputs[i] = avfilter_inout_alloc();
  
          if(graphInputs[i] == NULL)
  
              return -1;
  
      }
  
  
  
      //allocate input contexts
  
      inputContexts = av_calloc(inputCount + 1, sizeof(AVFilterContext *));
  
      //first is the background
  
      snprintf(args, sizeof(args), "video_size=%dx%d:pix_fmt=%d:time_base=1/1:pixel_aspect=0", bgFrame->width, bgFrame->height, bgFrame->format);
  
      returnCode = avfilter_graph_create_filter(&inputContexts[0], bufferSrc, "background", args, NULL, graph);
  
      if(returnCode < 0)
  
          return returnCode;
  
      graphInputs[0]->filter_ctx = inputContexts[0];
  
      graphInputs[0]->name = av_strdup("background");
  
      graphInputs[0]->next = graphInputs[1];
  
  
  
      //allocate the rest
  
      for(i = 1; i <= inputCount; i++)
  
      {
  
          AVCodecContext *codecCtx = codecContexts[i - 1];
  
          snprintf(args, sizeof(args), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
  
                      codecCtx->width, codecCtx->height, codecCtx->pix_fmt,
  
                      codecCtx->time_base.num, codecCtx->time_base.den,
  
                      codecCtx->sample_aspect_ratio.num, codecCtx->sample_aspect_ratio.den);
  
          snprintf(name, sizeof(name), "video_%d", i);
  
  
  
          returnCode = avfilter_graph_create_filter(&inputContexts[i], bufferSrc, name, args, NULL, graph);
  
          if(returnCode < 0)
  
              return returnCode;
  
  
  
          graphInputs[i]->filter_ctx = inputContexts[i];
  
          graphInputs[i]->name = av_strdup(name);
  
          graphInputs[i]->pad_idx = 0;
  
          if(i < inputCount)
  
          {
  
              graphInputs[i]->next = graphInputs[i + 1];
  
          }
  
          else
  
          {
  
              graphInputs[i]->next = NULL;
  
          }
  
      }
  
  
  
      //allocate outputs
  
      graphOutput = avfilter_inout_alloc();   
  
      returnCode = avfilter_graph_create_filter(&outputContext, bufferSink, "out", NULL, NULL, graph);
  
      if(returnCode < 0)
  
          return returnCode;
  
      graphOutput->filter_ctx = outputContext;
  
      graphOutput->name = av_strdup("out");
  
      graphOutput->next = NULL;
  
      graphOutput->pad_idx = 0;
  
  
  
      returnCode = avfilter_graph_parse_ptr(graph, filters, graphInputs, &graphOutput, NULL);
  
      if(returnCode < 0)
  
          return returnCode;
  
  
  
      returnCode = avfilter_graph_config(graph, NULL);
  
          return returnCode;
  
  
  
      return 0;
  
  }

  The filters argument of the function is passed on to avfilter_graph_parse_ptr and it can looks like this : [background] scale=512x512 [base]; [video_1] scale=256x256 [tmp_1]; [base][tmp_1] overlay=0:0 [out]

  The call breaks after the call to avfilter_graph_config with the warning :
  Output pad "default" with type video of the filter instance "background" of buffer not connected to any destination and the error Invalid argument.

  What is it that I am not doing correctly ?