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• ffmpeg : nvidia gpu performance sub-optimal

  3 août 2021, par david furst

  the problem seems fairly basic : i'd like to create thumbnails from incoming video in the shortest time possible, and i'm trying to do this by offloading processing to an nvidia gpu.

  


  while i run ffmpeg, i'm monitoring the gpu usage with the nvidia-smi utility. gpu usage never goes above 15% and the amount of time to encode the thumbnails with gpu is only 10% less than the time required without the gpu. these performance levels are very disappointing.

  


  my question : am i going about this the wrong way (and if so, how should i go about it), or is this gpu performance 'normal'/'reasonable' ?

  


  SYSTEM INFORMATION

  


  the machine is a desktop pc running windows 10, 8gb ram, intel i7-7700. the gpu is an nvidia quadro pro 4000 with cuda 11.4 installed. ffmpeg is version N-101372-gb5cb8c8767-g2fc309e699+4 (2021) running under mingw, with --enable-cuda --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-libnpp --enable-nvdec and --enable-nvenc.

  


  a typical ffmpeg command line i've used is :

  


   1 ffmpeg -hide_banner \
 2     -init_hw_device cuda=cuda:0 -filter_hw_device cuda \
 3     -hwaccel_output_format cuda \
 4     -i "$infile" \
 5     -vf "hwupload_cuda,scale_npp=w=200:h=150:format=yuv420p:interp_algo=lanczos,fps=1/1,hwdownload,format=yuv420p" \
 6     -y "$outdir/%08d.png"


  


  i've varied the above by supplementing some cuda-related parameters according to posts i've read here on stackoverflow and on the nvidia transcoding guide, but haven't been able to improve performance. adding any of -hwaccel cuda, -hwaccel cuvid, -hwaccel nvenc at the beginning of line 3 results in the error :
Impossible to convert between the formats supported by the filter 'graph 0 input from stream 0:0' and the filter 'auto_scaler_0'

  


  any pointers appreciated.

  


• ffmpeg creating mpeg-dash chunk files too slowly resulting in 404 errors

  17 juillet 2021, par Danny

  I have a hardware encoder feeding FFmpeg to create a MPEG-DASH Low Latency stream. It works well for a while, but after letting FFmpeg run for a while and reloading the page there are many 404 errors.

  


  When that happens, the dash.js player tries to fetch the segment file on the "live edge" but the file has not been created yet by FFmpeg. For example, after running for 20-30 minutes and loading the web page player, debug code in the web server shows :

  


  2021-07-16 16:46:30.64 : GET REQUEST : /data/ott/chunk-stream0-00702.m4s
2021-07-16 16:46:30.67 : NOT FOUND. Latest files on filesystem:
    chunk-stream0-00699.m4s.tmp
    chunk-stream0-00698.m4s
    chunk-stream0-00697.m4s
    chunk-stream0-00696.m4s
    ...


  


  So you can see the browser requested chunk 702 but the latest on the server is (part of) 699. With 2 second chunks, that is 3-5 seconds of content not yet available.

  


  To analyze, I modified FFmpeg's dashenc.c to add a timestamp every time a file is opened which displays like :

  


  [dash @ 0x9b17c0] 21:48:52.935 1626443332.935  : dashenc_io_open() - opened /data/ott/chunk-stream0-00060.m4s.tmp


  


  And loaded the timestamps into Excel.

  


  Despite a segment duration of 2.000 seconds, the average time between file opens is 2.011 seconds. Over two hours this accumulated to a 45 second difference between the calculated live edge and the latest file on the server.

  


  The HW encoder is set to 25 fps and a GOP size of 5. I've confirmed both by analyzing the H.264 NALUs output by the HW encoder.

  


  My Question : Is this a bug in FFmpeg or can I avoid this problem by adjusting the settings of either the HW encoder and/or FFmpeg options ?

  


  REFERENCE

  


  FFmpeg: Version 4.4 
Centos 8 
Apache 2.4.37


  


  FFmpeg command line (pipe is fed by process reading HW encoder)

  


  ffmpeg -re -loglevel verbose -an -f h264 -i pipe:17 -c:v copy \
-f dash -dash_segment_type mp4 -b:v 1000000 -seg_duration 2.000000 \
-frag_type duration -frag_duration 0.200000 -target_latency 1 \
-window_size 10 -extra_window_size 5 -remove_at_exit 1 -streaming 1 \
-ldash 1 -use_template 1 -use_timeline 0 -write_prft 1 -avioflags direct \
-fflags +nobuffer+flush_packets -format_options movflags=+cmaf \
-utc_timing_url /web/be/time.php /data/ott/master.mpd


  


  Modified dash_io_open() from dashenc.c

  


  static int 
dashenc_io_open(AVFormatContext *s, AVIOContext **pb, char *filename, AVDictionary **options)
{
    DASHContext *c = s->priv_data;
    int http_base_proto = filename ? ff_is_http_proto(filename) : 0;
    int err = AVERROR_MUXER_NOT_FOUND;
    if (!*pb || !http_base_proto || !c->http_persistent)
    {
        err = s->io_open(s, pb, filename, AVIO_FLAG_WRITE, options);

        // My Debug
        {
            char buf[20], milli[60];
            struct timeb tp;

            ftime(&tp); // sec + ms
            struct tm *tmInfo = localtime(&tp.time);

            // 2020-05-15 21:15:12.123
            strftime(buf, sizeof(buf), "%H:%M:%S", tmInfo);
            snprintf(milli, 59, "%s.%03d %d.%03d ", buf, tp.millitm, tp.time, tp.millitm);

            av_log(s, AV_LOG_INFO, "%s : dashenc_io_open() - opened %s\n", milli, filename);
        }
    }
    return err;
}


  


• Error while adding RTSP stream to Ant media server

  28 juillet 2021, par Jacob

  I have successfully remotely viewed the stream using ffplay -rtsp_transport tcp rtsp ://streamurl.

  


      ffplay version 4.4 Copyright (c) 2003-2021 the FFmpeg developers
  built with Apple clang version 12.0.5 (clang-1205.0.22.9)
  configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/4.4_2 --enable-shared --enable-pthreads --enable-version3 --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-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-avresample --enable-videotoolbox
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, rtsp, from 'rtsp://admin:lyne1234@74.65.209.152:554/11/stream1':
  Metadata:
    title           : 10
  Duration: N/A, start: 0.050000, bitrate: N/A
  Stream #0:0: Video: hevc (Main), yuvj420p(pc, bt709), 1920x1080, 20 fps, 20 tbr, 90k tbn, 20 tbc
[swscaler @ 0x160330000] deprecated pixel format used, make sure you did set range correctly
   5.69 M-V:  0.014 fd=   0 aq=    0KB vq=   97KB sq=    0B f=0/0   


  


  However, when playing the stream the a VCL player or trying to add the stream to my AWS instance of Ant media server. The stream does not go through. On ant media server there is no errors the stream connects but its just a black screen. On the VCL player I am getting the error :

  


  VLC is unable to open the MRL 'rtsp://{streamurl}'


  


  I currently have an identical camera setup the exact same way working fine. The only difference is there on different LAN's with different ISP's.