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• Can I use avcodec_free_context() on an opened context ?

  23 mars 2017, par Ashe the human

  The latest documentation says here that opening a context that’s closed again is not supported any more. I see why. Some codecs don’t work properly when they’re reopened. So after finding this bug, I decided to not use avcodec_close() and call avcodec_free_context() on the contexts right away instead.

  But I’m not sure if it’s safe to do so with 2.8.4, the version that I linked to my program. The documentation from that time doesn’t clarify. Does anyone know ? At least empirically ?

  ffmpeg version 2.8.4 Copyright (c) 2000-2015 the FFmpeg developers
  
  built with Microsoft (R) C/C++ 최적화 컴파일러 버전 18.00.31101(x64)
  
  configuration: --toolchain=msvc --enable-gpl --enable-nonfree --enable-nvenc --enable-libvorbis --enable-libmp3lame --enable-libtheora --enable-libx264 --enable-libx265 --enable-libxvid --enable-libopus --enable-libvpx --enable-static --disable-shared --disable-debug --extra-cflags=-MT --extra-cxxflags=-MT --extra-ldflags='/nodefaultlib:msvcrt.lib' --extra-libs='zlib.lib libogg_static.lib libvorbis_static.lib libmpghip-static.lib libmp3lame-static.lib libtheora_static.lib libx264.lib x265-static.lib libxvidcore.lib silk_fixed.lib silk_common.lib silk_float.lib celt.lib opus.lib vpxmt.lib'
  
  libavutil      54. 31.100 / 54. 31.100
  
  libavcodec     56. 60.100 / 56. 60.100
  
  libavformat    56. 40.101 / 56. 40.101
  
  libavdevice    56.  4.100 / 56.  4.100
  
  libavfilter     5. 40.101 /  5. 40.101
  
  libswscale      3.  1.101 /  3.  1.101
  
  libswresample   1.  2.101 /  1.  2.101
  
  libpostproc    53.  3.100 / 53.  3.100

  I know there’s a bunch of forums I could post on but I’d felt like to ask it here first.

• avconv / ffmpeg webcam capture while using minimum CPU processing

  10 septembre 2015, par user3585723

  I have a question about avconv (or ffmpeg) usage.

  My goal is to capture video from a webcam and saving it to a file.
  Also, I don’t want to use too much CPU processing. (I don’t want avconv to scale or re-encode the stream)

  So, I was thinking to use the compressed mjpeg video stream from the webcam and directly saving it to a file.

  My webcam is a Microsoft LifeCam HD 3000 and its capabilities are :

  ffmpeg -f v4l2 -list_formats all -i /dev/video0
  
  
  
  Raw: yuyv422 : YUV 4:2:2 (YUYV) : 640x480 1280x720 960x544 800x448 640x360 424x240 352x288 320x240 800x600 176x144 160x120 1280x800
  
  
  
  Compressed: mjpeg : MJPEG : 640x480 1280x720 960x544 800x448 640x360 800x600 416x240 352x288 176x144 320x240 160x120

  What would be the avconv command to save the Compressed stream directly without having avconv doing scaling or re-encoding.

  For now, I am using this command :

  avconv -f video4linux2 -r 30 -s 320x240 -i /dev/video0 test.avi

  I’m not sure that this command is CPU efficient since I don’t tell anywhere to use the mjpeg Compressed capability of the webcam.

  Is avconv taking care of the configuration of the webcam setting before starting to record the file ? Is it always working of raw stream and doing scaling and enconding on the raw stream ?

  Thanks for your answer

• fftools/ffmpeg_opt : Document VAAPI -device usage for DirectX Adapter

  14 avril 2023, par Sil Vilerino

  fftools/ffmpeg_opt : Document VAAPI -device usage for DirectX Adapter
  Initial review at https://github.com/intel-media-ci/ffmpeg/pull/619/
  Signed-off-by : Sil Vilerino <sivileri@microsoft.com>
  
  Reviewed-by : Dmitry Rogozhkin <dmitry.v.rogozhkin@intel.com>
  
  Reviewed-by : Wu, Tong1 <tong1.wu@intel.com>
  

  • [DH] doc/ffmpeg.texi
  • [DH] fftools/ffmpeg_opt.c