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• How to create thumbnails from HDR video with FFmpeg ?

  22 juin 2022, par schneikai

  I using FFmpeg to create thumbnails from HDR videos recorded with an iPhone but the colors of the generated JPG file look washed out. Here is a screenshot I took while running the video in a player and the other picture is a JPG generated with FFmpeg.

  


  Screenshot from Movie :

  


  

  


  Thumbnail from FFmpeg :

  


  

  


  Here´s a link to the mov-file : https://www.dropbox.com/s/udowplvfspxq6ag/IMG_8357.MOV?dl=1

  


  I use the standard command to generate the thumbnails : ffmpeg -i IMG_8357.MOV -vframes 1 output.jpg

  


  My FFmpeg Version is

  


  ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
built with Apple clang version 13.1.6 (clang-1316.0.21.2.5)
configuration: --prefix=/usr/local/Cellar/ffmpeg/5.0.1_1 --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-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --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-videotoolbox
libavutil      57. 17.100 / 57. 17.100
libavcodec     59. 18.100 / 59. 18.100
libavformat    59. 16.100 / 59. 16.100
libavdevice    59.  4.100 / 59.  4.100
libavfilter     8. 24.100 /  8. 24.100
libswscale      6.  4.100 /  6.  4.100
libswresample   4.  3.100 /  4.  3.100
libpostproc    56.  3.100 / 56.  3.100


  


  Thanks so much for pointing me in the right direction.

  


• FFMPEG : How to get video encoded with transparency ? [duplicate]

  23 juin 2022, par mnse_so

  I've an issue on ffmpeg usage. Guess it's my fault, but I don't understand why. I tried to study the documentation and the mass of google stuff regarding ffmpeg, but I did not find any hints for it which would help.

  


  The issue is following.

  


  I'm using ffmpeg with a pipe input as rawvideo (ARGB 8x8x8x8 pixel data). In general, it works and produces a correct video like a charm.
  
But now I'm stuck to get video with transparency, so I've changed to webm which supports transparency.

  


  As I can see on the log it uses rawvideo ARGB input as expected and do the export as vp9/yuva420p which should provide alpha support also as expected.

  


  ffmpeg.exe -y -use_wallclock_as_timestamps 1 -f rawvideo -pix_fmt argb -r 60.0 -s 600x600 -i - -q:v 0 video.webm

ffmpeg version 5.0.1-full_build-www.gyan.dev Copyright (c) 2000-2022 the FFmpeg developers
...
Input #0, rawvideo, from 'pipe:':
  Duration: N/A, start: 1655899073.916667, bitrate: 691200 kb/s
  Stream #0:0: Video: rawvideo (ARGB / 0x42475241), argb, 600x600, 691200 kb/s, 60 tbr, 60 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> vp9 (libvpx-vp9))
[libvpx-vp9 @ 0000027775a49f80] v1.11.0-133-ga3afed22a
[libvpx-vp9 @ 0000027775a49f80] Neither bitrate nor constrained quality specified, using default CRF of 32
Output #0, webm, to 'video.webm':
  Metadata:
    encoder         : Lavf59.16.100
  Stream #0:0: Video: vp9, yuva420p(tv, progressive), 600x600, q=2-31, 60 fps, 1k tbn
    Metadata:
      encoder         : Lavc59.18.100 libvpx-vp9
...
frame= ...


  


  But if I view the video it has no alpha.

  


  So, then I checked the video with ffprobe and to my surprise it now tells me that the stream is encoded by yuv420p which not providing alpha support !

  


  ffprobe.exe -i video.webm
ffprobe version 5.0.1-full_build-www.gyan.dev Copyright (c) 2007-2022 the FFmpeg developers
...
Input #0, matroska,webm, from 'video.webm':
  Metadata:
    ENCODER         : Lavf59.16.100
  Duration: N/A, start: 0.000000, bitrate: N/A
  Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv, progressive), 600x600, SAR 1:1 DAR 1:1, 60 fps, 60 tbr, 1k tbn
    Metadata:
      alpha_mode      : 1
      ENCODER         : Lavc59.18.100 libvpx-vp9
  


  


  I've also tried many this and that options from several google research but non of them leads to the goal.

  


  Any hints are welcome to get the video encoded with transparency.

  


  PS : I also checked that the input pixels used for pipe input are containing correct alpha information.

  


• Process in c# freezes up

  12 juillet 2022, par Quicksoapy

  environment : Rider 2022.1.2, .NET 6.0, Windows 10

  


  The following piece of code should copy the musicFile that is given and add a cover to the copy, then place it as name : title - artist.extension in the same directory, for example never gonna give you up - rick astley.mp3

  


  When debugging, if i copy-paste what is saved in the variable p.StartInfo.Argumentsin a CMD terminal, it works perfectly, but in my c# code the program freezes up at p.WaitForExit();.

  


  What could i be doing wrong ?

  


   using (Process p = new Process())
    {
        p.StartInfo.UseShellExecute = false;
        p.StartInfo.CreateNoWindow = true;
        p.StartInfo.RedirectStandardOutput = true;
        p.StartInfo.FileName = "CMD.exe";
        p.StartInfo.Arguments = "ffmpeg -i \""+ musicFile +"\" -i  \""+  albumInfo.Image.Uri.ToString() +"\" -map 0:a -map 1 -codec copy -metadata:s:v title=\"Album cover\" -metadata:s:v comment=\"Cover (front)\" -disposition:v attached_pic \"" + directoryFile + "\\" + title + " - " + artist + "." + formatName + "\"";
        p.Start();
        p.WaitForExit();
    }