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• avcodec/exr : preserve half-float NaN bits and add fate test

  23 novembre 2020, par Mark Reid

  avcodec/exr : preserve half-float NaN bits and add fate test
  Handles NaNs more like the official implementation handles them, preserving
  
  the original bits.
  

  • [DH] libavcodec/exr.c
  • [DH] tests/fate/image.mak
  • [DH] tests/ref/fate/exr-rgb-scanline-zip-half-0x0-0xFFFF

• Encoding MJPEG from webcam in UWP development with C#

  24 avril 2018, par Federico Parra

  this is my first question in StackOverflow.

  How can I encode video being captured from webcam as a MJPEG using C# in UWP enviroment (Visual Studio 2017) ?
  Perhaps using FFMPEG or DirectShow ? Any particular bindings required to use them in UWP ?

  I’ve been through these walk-throughs trying to go the official way using MediaCapture :

  https://docs.microsoft.com/en-us/windows/uwp/audio-video-camera/basic-photo-video-and-audio-capture-with-mediacapture
  https://docs.microsoft.com/en-us/uwp/api/windows.media.capture.mediacapture

  According to Microsoft though, there is no MJPEG encoder included in MediaEncoder (only decoder) : https://docs.microsoft.com/en-us/windows/uwp/audio-video-camera/supported-codecs

  About FFMPEG UWP integration, I found this :
  https://github.com/Microsoft/FFmpegInterop
  https://blogs.windows.com/buildingapps/2015/06/05/using-ffmpeg-in-windows-applications/#HHYbWAVcM7LhkvYZ.97

  But it’s geared towards decoding, and I want to encode.

  Just in case someone is wondering, I want to use MJPEG for Two reasons :
  1) less CPU intensive (much less) because it doesn’t do inter-frame compression, means my Surface Pro (and other similar computers) will keep quiet without fans running like crazy
  2) I need all frames (i.e. not one every 30) to be crystal clear because of an algorithm I need to run on each of them after

  Any pointers would be greatly appreciated.

  Thank you,
  Federico

• ffmpeg HLS multisize with no audio

  29 août 2021, par Konstantin

  I need to implement HLS video conversion and I've found a shell script that works almost perfectly. Here it is :

  


  VIDEO_IN=test.mov
VIDEO_OUT=master
HLS_TIME=4
FPS=25
GOP_SIZE=100
PRESET_P=veryslow
V_SIZE_1=960x540
V_SIZE_2=416x234
V_SIZE_3=640x360
V_SIZE_4=768x432
V_SIZE_5=1280x720
V_SIZE_6=1920x1080

# HLS
ffmpeg -i $VIDEO_IN -y \
    -preset $PRESET_P -keyint_min $GOP_SIZE -g $GOP_SIZE -sc_threshold 0 -r $FPS -c:v libx264 -pix_fmt yuv420p \
    -map v:0 -s:0 $V_SIZE_1 -b:v:0 2M -maxrate:0 2.14M -bufsize:0 3.5M \
    -map v:0 -s:1 $V_SIZE_2 -b:v:1 145k -maxrate:1 155k -bufsize:1 220k \
    -map v:0 -s:2 $V_SIZE_3 -b:v:2 365k -maxrate:2 390k -bufsize:2 640k \
    -map v:0 -s:3 $V_SIZE_4 -b:v:3 730k -maxrate:3 781k -bufsize:3 1278k \
    -map v:0 -s:4 $V_SIZE_4 -b:v:4 1.1M -maxrate:4 1.17M -bufsize:4 2M \
    -map v:0 -s:5 $V_SIZE_5 -b:v:5 3M -maxrate:5 3.21M -bufsize:5 5.5M \
    -map v:0 -s:6 $V_SIZE_5 -b:v:6 4.5M -maxrate:6 4.8M -bufsize:6 8M \
    -map v:0 -s:7 $V_SIZE_6 -b:v:7 6M -maxrate:7 6.42M -bufsize:7 11M \
    -map v:0 -s:8 $V_SIZE_6 -b:v:8 7.8M -maxrate:8 8.3M -bufsize:8 14M \
    -map a:0 -map a:0 -map a:0 -map a:0 -map a:0 -map a:0 -map a:0 -map a:0 -map a:0 -c:a aac -b:a 128k -ac 1 -ar 44100\
    -f hls -hls_time $HLS_TIME -hls_playlist_type vod -hls_flags independent_segments \
    -master_pl_name $VIDEO_OUT.m3u8 \
    -hls_segment_filename HLS/stream_%v/s%06d.ts \
    -strftime_mkdir 1 \
    -var_stream_map "v:0,a:0 v:1,a:1 v:2,a:2 v:3,a:3 v:4,a:4 v:5,a:5 v:6,a:6 v:7,a:7 v:8,a:8" HLS/stream_%v.m3u8


  


  It works as expected when test.mov has an audio track. But if it is, e.g. a screencast recorded with Quick Time with no audio track it will fail with this error :

  


  Stream map 'a:0' matches no streams.
To ignore this, add a trailing '?' to the map.


  


  I tried to do what it recommends and add ? to all audio mappings like :

  


  -map a:0?


  


  In this case it failed on -var_stream_map because it doesn't allow optional parameters.

  


  I've also found how to add an empty audio track here adding silent audio in ffmpeg

  


  But I had no luck trying to combine it with the script above.
Can anyone help me change the script so it could accept any files with and without audio ?

  


  p.s. I honestly read the official docs of ffmpeg but it didn't help at all