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• 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

  


• Audio and Video not synced after ffmpeg filter_complex select between

  2 février 2024, par RadekJ

  I am trying to trim a video shoot on an iPhone.

  


  When I execute :

  


  ffmpeg -i IMG_8555.MOV \
-filter_complex " \
[0:v] select='between(t,448.856,1279.240)', setpts=N/FR/TB; \
[0:a] aselect='between(t,448.856,1279.240)', asetpts=N/SR/TB \ 
" \ 
output.mov


  


  the output audio is out of sync - audio is faster (noticeable towards the end of the output video).

  


  I noticed that the outputs frame rate is 29.97 while the inputs is 29.98.

  


  So I did some experimenting and changed setpts to setpts=N/29.98/TB; but still the video is falling behind.
So I changed it even more to setpts=N/30.00/TB; - then it feels almost ok.

  


  I tired adding -vsync 1 - no luck

  


  I tried adding -async 1 - no luck

  


  I tried adding -async 7000 - no luck

  


  edit : If i put setpts=N/29.99/TB then it is ideal.

  


  Any ideas how can I make it always synced (no matter what is the input) ?

  


• Scenecut detection and consistent GOP size - adaptive streaming

  24 mars 2014, par Tarun

  Sample Command :

  -map 0:0 -f mp4 -vcodec libx264 -preset slow -profile:v main -vf scale="640:trunc(ow/a/2)*2" -vb 700k -minrate 650k -maxrate 750k -bufsize 10000k -an -g 48 -x264opts keyint=48:min-keyint=10:scenecut=40 -flags +cgop -sc_threshold 40 -pix_fmt yuv420p -threads 0 -y

  There is as such no error in encoding, But I wanted to understand following points-

  1) the above command will ensure that range of GOP size is 10,48, and if any scene change value (frame1 to fame2) is >40%, then a keyframe is introduced there ?

  2) So that means in a 3 hours of source video, there is no guarantee that GOP size will remain same

  3) No consider, I am creating 7 MP4 files each with different bitrate and resolution. (These Mp4s will be encoded to smooth in later stage). Hence i am targeting adaptive streaming. But when I did that, I found that if GOP sizes were not consistent across each bitrates. What I mean by this is, for ex : if in Bitrate1 - GOP size is like 10, 20, 48 and so on, in other bitrates it wasnt in the same sequence. I hope my question makes sense.

  So is there a way to ensure that GOP size may vary across one single output. But it should be consistent across each bitrate provided that the source is same ?

  Also for adaptive streaming Is scenecut detection advisable ?