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• How to convert fisheye-video into an equirectangular video to use with 360°-video viewers ?

  11 juin 2017, par P. Dee

  Actioncams like GoPro put a wider fov into a standard 1920 x 1080 or higher resolution at the expense of distortion.

  How do I use ffmpeg to convert this fov-encoded format into an equirectangular video to use with 360°-video viewers ?

• FFMpeg is slow on Android [duplicate]

  28 juin 2017, par Oleg Filimonov

  This question already has an answer here :

  • Precompiled FFmpeg for android versus building FFmpeg using android NDK
    
    2 answers
    
  • Fast Video Compression on Android
    
    2 answers
    

  I’m using this library : https://github.com/WritingMinds/ffmpeg-android

  Executing this command :

  ffmpeg -y -i video.mp4 -ignore_loop 0 -i overlay.gif -filter_complex `
  
  >> "[0][1]overlay=x=mod((1080/4 + sin(t)*1080/4)\,1920):y=mod(t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*1 + 1080/4 - sin(2*t)*1080/4)\,1920):y=mod(100 + t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*2 + 1080/4 - sin(-90 + t/2)*1080/4)\,1920):y=mod(150 + t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*3 + 1080/4 - sin(90 + 3*t)*1080/4)\,1920):y=mod(200 + t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*4 + 1080/4 - sin(180 + t)*1080/4)\,1920):y=mod(t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*5 + 1080/4 - sin(-180 + t)*1080/4)\,1920):y=mod(t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*6 + 1080/4 - sin(2*t)*1080/4)\,1920):y=100 + mod(100 + t*300\,1080):shortest=1[res]`
  
  >> " -map "[res]" -preset ultrafast out.mp4

  (Basically add a bunch of animated overlays to the video)

  On PC this command takes about a second to execute (render speed is about 278 fps). But on Android device with Snapdragon 821 it takes about 10 seconds (about 30 fps).

  The curious thing is that whenever command is executing on PC, CPU load is around 90%, but on Android it’s less than 1% (see screenshot : initial spike is UI stuff plus loading binaries, afterwards ffmpeg was executing until 10 second mark)

  

  I tried executing the same command, but writing to /dev/null
  instead of the file :

  ffmpeg -y -i video.mp4 -ignore_loop 0 -i overlay.gif -filter_complex `
  
  >> "[0][1]overlay=x=mod((1080/4 + sin(t)*1080/4)\,1920):y=mod(t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*1 + 1080/4 - sin(2*t)*1080/4)\,1920):y=mod(100 + t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*2 + 1080/4 - sin(-90 + t/2)*1080/4)\,1920):y=mod(150 + t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*3 + 1080/4 - sin(90 + 3*t)*1080/4)\,1920):y=mod(200 + t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*4 + 1080/4 - sin(180 + t)*1080/4)\,1920):y=mod(t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*5 + 1080/4 - sin(-180 + t)*1080/4)\,1920):y=mod(t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*6 + 1080/4 - sin(2*t)*1080/4)\,1920):y=100 + mod(100 + t*300\,1080):shortest=1[res]`
  
  >> " -map "[res]" -preset ultrafast -f null /dev/null

  This reduced time by 3 seconds.

  I also tried replacing gif overlay with png overlay, but speed didn’t improve significantly.

  Here’s log of the command execution on Android :

  ffmpeg version n3.0.1 Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 4.8 (GCC)
  
    configuration: --target-os=linux --cross-prefix=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/bin/arm-linux-androideabi- --arch=arm --cpu=cortex-a8 --enable-runtime-cpudetect --sysroot=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/sysroot --enable-pic --enable-libx264 --enable-libass --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-fontconfig --enable-pthreads --disable-debug --disable-ffserver --enable-version3 --enable-hardcoded-tables --disable-ffplay --disable-ffprobe --enable-gpl --enable-yasm --disable-doc --disable-shared --enable-static --pkg-config=/home/vagrant/SourceCode/ffmpeg-android/ffmpeg-pkg-config --prefix=/home/vagrant/SourceCode/ffmpeg-android/build/armeabi-v7a --extra-cflags='-I/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/include -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fno-strict-overflow -fstack-protector-all' --extra-ldflags='-L/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/lib -Wl,-z,relro -Wl,-z,now -pie' --extra-libs='-lpng -lexpat -lm' --extra-cxxflags=
  
    libavutil      55. 17.103 / 55. 17.103
  
    libavcodec     57. 24.102 / 57. 24.102
  
    libavformat    57. 25.100 / 57. 25.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 31.100 /  6. 31.100
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/data/user/0/com.example.user.proofofconcept/files/in_10s.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      creation_time   : 2017-06-27 18:07:54
  
    Duration: 00:00:10.47, start: 0.000000, bitrate: 14043 kb/s
  
      Stream #0:0(eng): Video: h264 (Baseline) (avc1 / 0x31637661), yuvj420p(pc, smpte170m), 1280x720, 13971 kb/s, 29.86 fps, 30.01 tbr, 90k tbn, 180k tbc (default)
  
      Metadata:
  
        creation_time   : 2017-06-27 18:07:53
  
        handler_name    : VideoHandle
  
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 96 kb/s (default)
  
      Metadata:
  
        creation_time   : 2017-06-27 18:07:54
  
        handler_name    : SoundHandle
  
  Input #1, gif, from '/data/user/0/com.example.user.proofofconcept/files/overlay.gif':
  
    Duration: N/A, bitrate: N/A
  
      Stream #1:0: Video: gif, bgra, 130x98, 6.17 fps, 4.92 tbr, 100 tbn, 100 tbc
  
  [swscaler @ 0xeddb3000] deprecated pixel format used, make sure you did set range correctly
  
  [libx264 @ 0xee1fdc00] using cpu capabilities: none!
  
  [libx264 @ 0xee1fdc00] profile Constrained Baseline, level 3.2
  
  [libx264 @ 0xee1fdc00] 264 - core 148 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=0 intra_refresh=0 rc=crf mbtree=0 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0
  
  Output #0, mp4, to '/storage/emulated/0/temp/out.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.25.100
  
      Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x720, q=-1--1, 30.01 fps, 90k tbn, 30.01 tbc (default)
  
      Metadata:
  
        encoder         : Lavc57.24.102 libx264
  
      Side data:
  
        unknown side data type 10 (24 bytes)
  
  Stream mapping:
  
    Stream #0:0 (h264) -> overlay:main
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    overlay -> Stream #0:0 (libx264)
  
  Press [q] to stop, [?] for help
  
  frame=   16 fps=0.0 q=24.0 size=     227kB time=00:00:00.29 bitrate=6210.2kbits/s dup=2 drop=0 speed=0.56x    
  
  frame=   29 fps= 28 q=24.0 size=     451kB time=00:00:00.73 bitrate=5042.1kbits/s dup=2 drop=0 speed=0.707x    
  
  frame=   40 fps= 26 q=24.0 size=     637kB time=00:00:01.09 bitrate=4744.5kbits/s dup=2 drop=0 speed=0.71x    
  
  frame=   57 fps= 28 q=24.0 size=     903kB time=00:00:01.66 bitrate=4441.3kbits/s dup=2 drop=0 speed=0.812x    
  
  frame=   75 fps= 29 q=24.0 size=    1186kB time=00:00:02.26 bitrate=4288.0kbits/s dup=2 drop=0 speed=0.885x    
  
  frame=   94 fps= 31 q=24.0 size=    1456kB time=00:00:02.89 bitrate=4113.4kbits/s dup=2 drop=0 speed=0.945x    
  
  frame=  113 fps= 32 q=25.0 size=    1780kB time=00:00:03.53 bitrate=4127.3kbits/s dup=2 drop=0 speed=0.985x    
  
  frame=  131 fps= 32 q=24.0 size=    2101kB time=00:00:04.13 bitrate=4165.9kbits/s dup=2 drop=0 speed=1.01x    
  
  frame=  150 fps= 33 q=24.0 size=    2461kB time=00:00:04.76 bitrate=4231.2kbits/s dup=2 drop=0 speed=1.03x    
  
  frame=  165 fps= 32 q=24.0 size=    2721kB time=00:00:05.26 bitrate=4234.1kbits/s dup=2 drop=0 speed=1.03x    
  
  frame=  185 fps= 33 q=24.0 size=    3028kB time=00:00:05.93 bitrate=4182.4kbits/s dup=2 drop=0 speed=1.05x    
  
  frame=  205 fps= 33 q=24.0 size=    3329kB time=00:00:06.59 bitrate=4133.3kbits/s dup=2 drop=0 speed=1.07x    
  
  frame=  224 fps= 34 q=24.0 size=    3610kB time=00:00:07.23 bitrate=4089.7kbits/s dup=2 drop=0 speed=1.08x    
  
  frame=  243 fps= 34 q=24.0 size=    3901kB time=00:00:07.86 bitrate=4063.3kbits/s dup=2 drop=0 speed=1.09x    
  
  frame=  264 fps= 34 q=24.0 size=    4297kB time=00:00:08.56 bitrate=4110.6kbits/s dup=2 drop=0 speed=1.11x    
  
  frame=  284 fps= 35 q=24.0 size=    4601kB time=00:00:09.23 bitrate=4083.5kbits/s dup=2 drop=0 speed=1.12x    
  
  frame=  304 fps= 35 q=24.0 size=    4886kB time=00:00:09.89 bitrate=4044.4kbits/s dup=2 drop=0 speed=1.14x    
  
  frame=  314 fps= 35 q=-1.0 Lsize=    5138kB time=00:00:10.46 bitrate=4022.4kbits/s dup=2 drop=0 speed=1.16x    
  
  video:5135kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.040961%
  
  [libx264 @ 0xee1fdc00] frame I:2     Avg QP:20.50  size: 84700
  
  [libx264 @ 0xee1fdc00] frame P:312   Avg QP:24.06  size: 16310
  
  [libx264 @ 0xee1fdc00] mb I  I16..4: 100.0%  0.0%  0.0%
  
  [libx264 @ 0xee1fdc00] mb P  I16..4:  7.7%  0.0%  0.0%  P16..4: 54.9%  0.0%  0.0%  0.0%  0.0%    skip:37.4%
  
  [libx264 @ 0xee1fdc00] coded y,uvDC,uvAC intra: 62.7% 22.9% 3.4% inter: 26.1% 8.4% 0.9%
  
  [libx264 @ 0xee1fdc00] i16 v,h,dc,p: 13% 14% 59% 13%
  
  [libx264 @ 0xee1fdc00] i8c dc,h,v,p: 47% 24% 22%  6%
  
  [libx264 @ 0xee1fdc00] kb/s:4020.26
  
   Success
  
  time used: 9843

  So what could be the reason of such low CPU load ?

• FFmpeg filtergraph memory leak

  5 juillet 2017, par Leif Andersen

  I have an FFmpeg program that :

  1. Demuxes and decodes a video file.
  2. Passes it through a filtergraph
  3. encodes and muxes the new video.

  The filtergraph itself is rather complex, and can be run directly from the command line as such :

  ffmpeg -i demo.mp4 -filter_complex \
  
   "[audio3]atrim=end=30:start=10[audio2];\
  
    [video5]trim=end=30:start=10[video4];[audio2]anull[audio6];\
  
    [video4]scale=width=1920:height=1080[video7];[audio6]anull[audio8];\
  
    [video7]fps=fps=30[video9];[audio8]anull[audio10];\
  
    [video9]format=pix_fmts=yuv420p[video11];\
  
    [audio10]asetpts=expr=PTS-STARTPTS[audio12];\
  
    [video11]setpts=expr=PTS-STARTPTS[video13];\
  
    [audio15]concat=v=0:a=1:n=1[audio14];\
  
    [video17]concat=v=1:a=0:n=1[video16];\
  
    [audio12]afifo[audio15];[video13]fifo[video17];\
  
    [audio14]afifo[audio18];[video16]fifo[video19];\
  
    [audio18]anull[audio20];\
  
    [video19]pad=width=1920:height=1080[video21];\
  
    [audio20]anull[audio22];[video21]fps=fps=25[video23];\
  
    [audio22]aformat=sample_fmts=fltp:sample_rates=44100:channel_layouts=stereo[fa];\
  
    [video23]format=pix_fmts=yuv420p[fv];[0:a]afifo[audio3];\
  
    [0:v]fifo[video5]" \
  
  -map "[fv]" -map "[fa]" out.mp4

  I realize this is a massive filtergraph with a lot of no-op filters, it was autogenerated rather than being hand written. Here is a more cleaner version of the graph. (Its a graphviz file, you can run it in the command line or here.)

  Anyway, when I run the program that uses this filtergraph my memory usage spikes. I end up using about 7 GB of RAM for a 30 second clip. However, when I run the program using the ffmpeg command above, it peaks out at about 600 MB of RAM. This causes me to believe that the problem is not the ungodly size of the filtergraph, but a problem with how my program is using it.

  The program sets up the filtergraph (using av_filter_parse_ptr, giving the filtergraph string shown above), encoder, muxer, decoder, and demuxer, then spawns two threads, one that sends frames into the filtergraph, and one that receives them. The frame that sends them looks something like :

  void decode () {
  
      while(... more_frames ...) {
  
          AVFrame *frame = av_frame_alloc();
  
          ... fill next frame of stream ...
  
          av_buffersrc_write_frame(ctx, frame);
  
          av_frame_free(&frame);
  
      }
  
  }

  (I have elided the av_send_packet/av_receive_frame functions as they don’t seem to be leaking memory. I have also elided the process of flushing the buffersrc as that won’t happen until the end, and the memory spikes long before that.)

  And the encoder thread looks similar :

  void encode() {
  
      while(... nodes_in_graph ...) {
  
          AVFrame *frame = av_frame_alloc();
  
          av_buffersink_get_frame(ctx, frame);
  
          ... ensure frame actually was filled ...
  
          ... send frame to encoder ...
  
          av_frame_free(&frame);
  
      }
  
  }

  As with the decoder, I have elided the send_frame/receive_packet combo as they don’t seem to be leaking memory. Additionally I have elided the details of ensuring that the frame actually was filled. The code loops until the frame eventually does get filled.

  Every frame I allocate I fairly quickly deallocate. I additionally handled all of the error cases that the ffmpeg can give (Elided in the example).

  I have also tried having only one frame for the encoder and one for the decoder (and calling av_frame_unref in each iteration of the loop).

  Am I forgetting to free something, or am I just using the calls to libavfilter incorrectly such that it has to buffer all of the data ? I don’t think the leak is caused by the memory graph because running it from the command line doesn’t seem to cause the same memory explosion.

  FWIW, the actual code is here, although its written in Racket. I do have a minimal example that also seems to duplicate this behavior (modified from the doc/example/filtering_video.c file from the ffmpeg code :

  #include 
  
  
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libavfilter></libavfilter>avfiltergraph.h>
  
  #include <libavfilter></libavfilter>buffersink.h>
  
  #include <libavfilter></libavfilter>buffersrc.h>
  
  #include <libavutil></libavutil>opt.h>
  
  
  
  const char *filter_descr = "trim=start=10:end=30,scale=78:24,transpose=cclock";
  
  
  
  static AVFormatContext *fmt_ctx;
  
  static AVCodecContext *dec_ctx;
  
  AVFilterContext *buffersink_ctx;
  
  AVFilterContext *buffersrc_ctx;
  
  AVFilterGraph *filter_graph;
  
  static int video_stream_index = -1;
  
  static int64_t last_pts = AV_NOPTS_VALUE;
  
  
  
  static int open_input_file(const char *filename)
  
  {
  
      int ret;
  
      AVCodec *dec;
  
  
  
      if ((ret = avformat_open_input(&amp;fmt_ctx, filename, NULL, NULL)) &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
  
          return ret;
  
      }
  
  
  
      if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
  
          return ret;
  
      }
  
  
  
      /* select the video stream */
  
      ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &amp;dec, 0);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot find a video stream in the input file\n");
  
          return ret;
  
      }
  
      video_stream_index = ret;
  
  
  
      /* create decoding context */
  
      dec_ctx = avcodec_alloc_context3(dec);
  
      if (!dec_ctx)
  
          return AVERROR(ENOMEM);
  
      avcodec_parameters_to_context(dec_ctx, fmt_ctx->streams[video_stream_index]->codecpar);
  
      av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);
  
  
  
      /* init the video decoder */
  
      if ((ret = avcodec_open2(dec_ctx, dec, NULL)) &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot open video decoder\n");
  
          return ret;
  
      }
  
  
  
      return 0;
  
  }
  
  
  
  static int init_filters(const char *filters_descr)
  
  {
  
      char args[512];
  
      int ret = 0;
  
      AVFilter *buffersrc  = avfilter_get_by_name("buffer");
  
      AVFilter *buffersink = avfilter_get_by_name("buffersink");
  
      AVFilterInOut *outputs = avfilter_inout_alloc();
  
      AVFilterInOut *inputs  = avfilter_inout_alloc();
  
      AVRational time_base = fmt_ctx->streams[video_stream_index]->time_base;
  
      enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
  
  
  
      filter_graph = avfilter_graph_alloc();
  
      if (!outputs || !inputs || !filter_graph) {
  
          ret = AVERROR(ENOMEM);
  
          goto end;
  
      }
  
  
  
      /* buffer video source: the decoded frames from the decoder will be inserted here. */
  
      snprintf(args, sizeof(args),
  
              "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
  
              dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,
  
              time_base.num, time_base.den,
  
              dec_ctx->sample_aspect_ratio.num, dec_ctx->sample_aspect_ratio.den);
  
  
  
      ret = avfilter_graph_create_filter(&amp;buffersrc_ctx, buffersrc, "in",
  
                                     args, NULL, filter_graph);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
  
          goto end;
  
      }
  
  
  
      /* buffer video sink: to terminate the filter chain. */
  
      ret = avfilter_graph_create_filter(&amp;buffersink_ctx, buffersink, "out",
  
                                         NULL, NULL, filter_graph);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
  
          goto end;
  
      }
  
  
  
      ret = av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts,
  
                                AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
  
          goto end;
  
      }
  
  
  
      outputs->name       = av_strdup("in");
  
      outputs->filter_ctx = buffersrc_ctx;
  
      outputs->pad_idx    = 0;
  
      outputs->next       = NULL;
  
      inputs->name       = av_strdup("out");
  
      inputs->filter_ctx = buffersink_ctx;
  
      inputs->pad_idx    = 0;
  
      inputs->next       = NULL;
  
  
  
      if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
  
                                      &amp;inputs, &amp;outputs, NULL)) &lt; 0)
  
          goto end;
  
  
  
      if ((ret = avfilter_graph_config(filter_graph, NULL)) &lt; 0)
  
          goto end;
  
  
  
  end:
  
      avfilter_inout_free(&amp;inputs);
  
      avfilter_inout_free(&amp;outputs);
  
  
  
      return ret;
  
  }
  
  
  
  int main(int argc, char **argv)
  
  {
  
      int ret;
  
      AVPacket packet;
  
      AVFrame *frame = av_frame_alloc();
  
      AVFrame *filt_frame = av_frame_alloc();
  
  
  
      if (!frame || !filt_frame) {
  
          perror("Could not allocate frame");
  
          exit(1);
  
      }
  
      if (argc != 2) {
  
          fprintf(stderr, "Usage: %s file\n", argv[0]);
  
          exit(1);
  
      }
  
  
  
      av_register_all();
  
      avfilter_register_all();
  
  
  
      if ((ret = open_input_file(argv[1])) &lt; 0)
  
          goto end;
  
      if ((ret = init_filters(filter_descr)) &lt; 0)
  
          goto end;
  
  
  
      /* read all packets */
  
      while (1) {
  
          if ((ret = av_read_frame(fmt_ctx, &amp;packet)) &lt; 0)
  
              break;
  
  
  
          if (packet.stream_index == video_stream_index) {
  
              ret = avcodec_send_packet(dec_ctx, &amp;packet);
  
              if (ret &lt; 0) {
  
                  av_log(NULL, AV_LOG_ERROR, "Error while sending a packet to the decoder\n");
  
                  break;
  
              }
  
  
  
              while (ret >= 0) {
  
                  ret = avcodec_receive_frame(dec_ctx, frame);
  
                  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
  
                      break;
  
                  } else if (ret &lt; 0) {
  
                      av_log(NULL, AV_LOG_ERROR, "Error while receiving a frame from the decoder\n");
  
                      goto end;
  
                  }
  
  
  
                  if (ret >= 0) {
  
                       frame->pts = av_frame_get_best_effort_timestamp(frame);
  
  
  
                      /* push the decoded frame into the filtergraph */
  
                      if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) &lt; 0) {
  
                          av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
  
                          break;
  
                      }
  
  
  
                      /* pull filtered frames from the filtergraph */
  
                      while (1) {
  
                          ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
  
                          if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
  
                              break;
  
                          if (ret &lt; 0)
  
                              goto end;
  
                          av_frame_unref(filt_frame);
  
                      }
  
                      av_frame_unref(frame);
  
                  }
  
              }
  
          }
  
          av_packet_unref(&amp;packet);
  
      }
  
  end:
  
      avfilter_graph_free(&amp;filter_graph);
  
      avcodec_free_context(&amp;dec_ctx);
  
      avformat_close_input(&amp;fmt_ctx);
  
      av_frame_free(&amp;frame);
  
      av_frame_free(&amp;filt_frame);
  
  
  
      return ret;
  
  }