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• MPEG-4 and alpha transparency - the ongoing saga

  6 décembre 2022, par OrangeDog

  I'd like to reach some sort of definitive answer for the following questions :

  



  

  1. Is alpha transparency supported in MPEG-4-based codecs ?

  


  2. Is there any way to be reasonably certain that there is no alpha-channel from the output of ffprobe ?

  


  



  Some links I've found on the subject :

  



  

  • https://stackoverflow.com/a/5057631/476716

  


  



  


  Also, transparent alpha layers, an optional part of the H.264 specification, are now supported in H.264-based QuickTime movies.

  


  



  

  • http://software.intel.com/en-us/articles/alpha-channel-support-in-the-h264-decoder-in-ipp/

  


  



  


  The support for alpha channel in the H.264 decoder is now available in Intel® Integrated Performance Primitives 6.0 version.

  


  



  

  • http://forums.creativecow.net/readpost/335/30475

  


  



  


  The MPEG4 Simple Studio Profile supports auxiliary channels, which could be used for alpha or depth — and presumably even displacement, motion vectors, normals, etc.

  


  



  However, I've never seen a concrete example, or indeed any details on how you use these announced features.

  


• How to convert png images to a HEVC(h265) video with alpha

  20 décembre 2022, par ImWH

  I want to convert a sequence of png images to a HEVC video with alpha, I would like to use ffmpeg to do this work and find the following command(images name are p01.png, p02.png...) :

  


  ffmpeg -framerate 10 -i p%02d.png -c:v hevc_videotoolbox -require_sw 1 -allow_sw 1 -alpha_quality 0.5 -vtag hvc1 hevc.mov


  


  the print is here :

  


  ffmpeg version 5.1.2 Copyright (c) 2000-2022 the FFmpeg developers
  built with Apple clang version 14.0.0 (clang-1400.0.29.202)
  configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/5.1.2_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 --enable-neon
  libavutil      57. 28.100 / 57. 28.100
  libavcodec     59. 37.100 / 59. 37.100
  libavformat    59. 27.100 / 59. 27.100
  libavdevice    59.  7.100 / 59.  7.100
  libavfilter     8. 44.100 /  8. 44.100
  libswscale      6.  7.100 /  6.  7.100
  libswresample   4.  7.100 /  4.  7.100
  libpostproc    56.  6.100 / 56.  6.100
Input #0, image2, from 'p%02d.png':
  Duration: 00:00:09.60, start: 0.000000, bitrate: N/A
  Stream #0:0: Video: png, rgba(pc), 375x812 [SAR 3779:3779 DAR 375:812], 10 fps, 10 tbr, 10 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (png (native) -> hevc (hevc_videotoolbox))
Press [q] to stop, [?] for help
[1]    16348 trace trap  ffmpeg -framerate 10 -i p%02d.png -c:v hevc_videotoolbox -require_sw 1  1  0.


  


  It seems like there is no error and the video has been generated but the size of video is always 0kb, I try to change the parameter for command but nothing changed, so is there something working with the command ? or Is there is a simple way to create the HEVC video using png image ? Thanks

  


  My Environment :
Apple silicon(MacBook with M1 Pro clip) Mac OS 13.0
ffmpeg : 5.1.2

  


• Ffmpeg : How to transition 2 videos together with a custom alpha channel video

  9 janvier 2023, par Daniel Enrico Botta

  I have these files :

  


  

  • 1.mp4, 2.mp4 (video files)

  


  • wipe.mov (alpha channel wipe)

  


  


  I want to use the wipe.mov as a transition between 1.mp4 and 2.mp4
The wipe.mov should replicate the same feeling as the xfade=transition=wipeleft with the only difference that it should use wipe.mov as input

  


  I have tried to use alphaextract to extract the alphachannel from the wipe.mov and this seems to work well.

  


  The problem is I can't figure out how to overlay and make transparent the correct portions in order to make this.

  


  Unfortunately xfade does not accept a video as input... I had tried something like this :

  


  ffmpeg -y -hide_banner -i 1.mp4 -i 2.mp4 -i wipe.mov -filter_complex \ "[0:v]settb=AVTB,setpts=PTS-STARTPT[v0];[1:v]settb=AVTB,setpts=PTS-STARTPTS\[v1]; \ [v1]scale=1280x720,format=yuva420p,alphaextract[alpha]; \ [v0][alpha]xfade=transition=custom:duration=1[out]" -map "[out]" output.mp4

  


  Does anyone know a way to make this work ?

  


  I have also been looking into lumakey...

  


  UPDATE :

  


  this is what I want to achieve :

  


  https://drive.google.com/file/d/1fBu3bVmtbu5DtxEWAzADRmoVCeCg—tD/view?usp=share_link

  


  this is the wipe.mov :

  


  https://drive.google.com/file/d/1z83chzDe0Iw-oTEduWXBpueIAoZezODD/view?usp=share_link