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• FFmpeg — Using hardware acceleration for video decoding

  5 novembre 2018, par Paul Belanger

  I have a project that uses FFmpeg to decode video streams and I want to make use of hardware decoding where available. According to this answer, the use of ff_find_hwaccel and friends is deprecated in newer FFmpeg builds.

  The answer states that ff_find_hwaccel is deprecated. I want to know how the new method for allocating a hardware accelerated decoder works. Is it done automatically ? Can I just pass hwaccel in an AvDictionary as the third option to avcodec_open2, or do I have to do something more involved ?

  Currently the code for allocating an AVCodecContext looks like this :

  auto video_codec = avcodec_find_decoder(codec_id);
  
  auto context = avcodec_alloc_context3(video_codec);
  
  auto retcode = avcodec_open2(context, video_codec, nullptr);

  with error checking, of course.

  I then push AVPackets into the decoder using avcodec_decode_video2.

• Ffmpeg hardware acceleration unsupported formats betwen transpose and auto_scaler_0

  11 août 2021, par Eduard6421

  I am trying to develop a transoding service which makes use of nvidia hardware acceleration capabilities ( The gpu used in this process is a Tesla T4) ; I want to generate a mpeg-dash playlist for my video so that i can stream it ;

  


  ffmpeg -y -hwaccel cuda -hwaccel_output_format cuda -i mobil1.mp4 -c:v h264_nvenc -c:a aac  \
-map v:0 -b:v:0 1000k -maxrate:0 1500k -bufsize:0 2500k -filter:v:0 "scale_npp=1920:1080:force_original_aspect_ratio=decrease" -map 0:a -b:a 128k \
-f dash dash.mpd


  


  But when mobile videos are uploaded ( which have rotation metadata ) I encounter the following error :

  


  Impossible to convert between the formats supported by the filter 'transpose' and the filter 'auto_scaler_0'
Error reinitializing filters!
Failed to inject frame into filter network: Function not implemented
Error while processing the decoded data for stream #0:0


  


  How can i solve this issue ? I am using the following docker image :
jrottenberg/ffmpeg:4.4-nvidia

  


• FFmpeg decode video to lossless frames hardware acceleration CUDA

  29 décembre 2020, par Seva Safris

  I have 1 second H.265-encoded videos at 30 fps coming into a server for processing. The server needs to decode the videos into individual frames (lossless). These videos are coming in very quickly, so performance is of utmost importance. The server has a H.265 compatible Nvidia GPU, and I have built ffmpeg with support for CUDA. The following is the configuration output from ffmpeg :

  


  ffmpeg version N-100479-gd67c6c7f6f Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 8 (Ubuntu 8.4.0-3ubuntu2)
  configuration: --enable-nonfree --enable-cuda-nvcc --enable-nvenc --enable-opencl --enable-shared
                 --enable-pthreads --enable-version3 --enable-avresample --enable-ffplay --enable-gnutls
                 --enable-gpl --disable-libaom --disable-libbluray --disable-libdav1d 
                 --disable-libmp3lame --enable-libopus --disable-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 --disable-libopenjpeg --enable-librtmp --enable-libspeex
                 --enable-libsoxr --disable-videotoolbox --disable-libjack --disable-indev=jack
                 --extra-cflags=-I/usr/local/cuda/include --extra-ldflags=-L/usr/local/cuda/lib64


  


  I decode the videos into PNGs, and am using the following command :

  


  ffmpeg -y -vsync 0 -hwaccel cuvid -hwaccel_output_format cuda -hwaccel_device 0 -c:v hevc_cuvid \
       -i 0.mp4 -vf hwdownload,format=nv12 -q:v 1 -qmin 1 -qmax 1 -start_number 0 f%d.png


  


  This command successfully leverages the hardware acceleration for the H.265 decode. But, the PNG encode is done by the CPU.

  


  Does CUDA have support for encoding of lossless images ? The format does not need to be PNG, but it does need to be lossless. CUDA has a nvJPEG Library, but JPEG is a lossy format. Is there a similar image encoding library in CUDA for a lossless format (that is also integrated with ffmpeg) ?

  


  Edit : Some more context....

  


  I am currently using PNGs because of their compression-ability. These images are 2560x1280 in size, btw. On one hand, it is this compression that costs the CPU cycles. On the other hand, I am also limited by the throughput of how fast (and how much aggregate data) can I upload these frames to the upstream consumer. So it's basically a tradeoff between :

  


  

  1. We want to extract these frames as quickly as possible.

  


  2. We want efficiency regarding the image size.