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• x86/tx_float : implement inverse MDCT AVX2 assembly

  3 septembre 2022, par Lynne

  x86/tx_float : implement inverse MDCT AVX2 assembly
  This commit implements an iMDCT in pure assembly.
  This is capable of processing any mod-8 transforms, rather than just
  
  power of two, but since power of two is all we have assembly for
  
  currently, that's what's supported.
  
  It would really benefit if we could somehow use the C code to decide
  
  which function to jump into, but exposing function labels from assebly
  
  into C is anything but easy.
  
  The post-transform loop could probably be improved.
  This was somewhat annoying to write, as we must support arbitrary
  
  strides during runtime. There's a fast branch for stride == 4 bytes
  
  and a slower one which uses vgatherdps.
  Zen 3 benchmarks for stride == 4 for old (av_imdct_half) vs new (av_tx) :
  128pt :
  
     2811 decicycles in         av_tx (imdct),16775916 runs,   1300 skips
  
     3082 decicycles in         av_imdct_half,16776751 runs,    465 skips
  256pt :
  
     4920 decicycles in         av_tx (imdct),16775820 runs,   1396 skips
  
     5378 decicycles in         av_imdct_half,16776411 runs,    805 skips
  512pt :
  
     9668 decicycles in         av_tx (imdct),16775774 runs,   1442 skips
  
    10626 decicycles in         av_imdct_half,16775647 runs,   1569 skips
  1024pt :
  
    19812 decicycles in         av_tx (imdct),16777144 runs,     72 skips
  
    23036 decicycles in         av_imdct_half,16777167 runs,     49 skips
  

  • [DH] libavutil/tx.c
  • [DH] libavutil/tx_priv.h
  • [DH] libavutil/x86/tx_float.asm
  • [DH] libavutil/x86/tx_float_init.c

• I would like to batch-trim mp4 videos in a folder with command line (ffmpeg ?), however the sound is delayed

  28 janvier 2023, par pdeli

  I found the following command line to batch-trim videos in a folder, however it delays the sound of all the videos by a few seconds (sound comes after the video) :

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -ss 00:00:08 -c copy -avoid_negative_ts 1 "${file%.*}_trimmed.mp4"; done

  


  These are the alternatives I found, however none of them solve the problem :

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -itsoffset -0.5 -ss 8 -c:v copy -c:a copy "${file%.*}_trimmed.mp4"; done

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -ss 8 -async 1 -c:v copy -c:a copy "${file%.*}_trimmed.mp4"; done

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -ss 8 -map 0:v -map 0:a -c:v copy -c:a copy "${file%.*}_trimmed.mp4"; done

  


  I have a hard time finding by how much time the sound is delayed.

  


  My questions :

  


  

  • what would be the command line to batch-trim the beginning of all the videos in a folder with the sound properly "aligned" to the video ?

  


  • in other words, can't the sound be by default trimmed by as much as the video in the first place ? If yes, how ?

  


  


  ---

  


  System used :

  


  

  • macOS Ventura (13.1, Intel)

  


  • Shell and version : zsh 5.8.1 (x86_64-apple-darwin22.0)

  


  • ffmpeg version 5.0 built with Apple clang version 13.0.0 (clang-1300.0.29.30)

  


  


• hevc_videotoolbox encoding failed

  19 avril, par TheCoderPro

  I have some downloaded My Hero Academia episodes, and I'm trying to put them on my iPad that hasn't got that much space. So, I decided to try convert them to HEVC. But, when I try to use hevc_videotoolbox for GPU acceleration. But, it doesn't work.

  


  input command : ffmpeg -i /Volumes/SSD\ STORAGE/MHA/S2/S02E00.mp4 -b:v 640k /Volumes/SSD\ STORAGE/MHA/S2/S02E00_0640.mp4

  


  Output :

  


  ffmpeg version 4.4.1 Copyright (c) 2000-2021 the FFmpeg developers
  built with Apple clang version 13.0.0 (clang-1300.0.29.3)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.4.1 --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-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --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-avresample --enable-videotoolbox
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/Volumes/SSD STORAGE/MHA/S2/S02E00.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.27.104
  Duration: 00:23:59.98, start: 0.000000, bitrate: 2018 kb/s
  Stream #0:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 1758 kb/s, 23.98 fps, 23.98 tbr, 11988 tbn, 47.95 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 253 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> hevc (hevc_videotoolbox))
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[hevc_videotoolbox @ 0x7fd88481bc00] Error encoding frame: -12905
[hevc_videotoolbox @ 0x7fd88481bc00] popping: -542398533
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
[aac @ 0x7fd88480d800] Qavg: 52341.500
[aac @ 0x7fd88480d800] 2 frames left in the queue on closing
Conversion failed!


  


  The file also gets created but it's empty (0 bytes)