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• How to do precise frame cut with ffmpeg ?

  25 juillet 2020, par Menglun Li

  I tried to cut multiple big videos into many small pieces. I know I can cut and export the small pieces one by one with "Premiere Elements", however that takes a lot time to export them manually. I couldn't find a way to do batch export in "Premiere Elements".

  


  I wrote down the starting and ending points of the small videos from Premiere Elements' timeline viewer, then I created a batch file to use ffmpeg for batch cutting. Below is one of the cutting command in the batch file.

  


  ffmpeg -i input.mp4 -ss 00:20:45.09 -to 00:23:01.00 -c:v libx264 -c:a aac output5.mp4 


  


  I compared the video that was cut by ffmpeg and the video was exported by Premiere Elements. I found sometime they are not starting and ending at the same frame, and it is not consistent either. Both the starting and ending frame that was cut by ffmpeg can drift forward or backward 6-9 frames from the frame number showed in Premiere Elements.

  


  How do I make sure ffmpeg has the precise frame cut ? Thanks in advance.

  


• Seeking Guidance on Audio Development Libraries for Playing Various Music Formats on iOS [closed]

  3 décembre 2023, par FaiChou

  I am exploring audio development and am overwhelmed by the numerous libraries available :

  


  

  • AVFoundation

  


  • MediaPlayer

  


  • AVFAudio

  


  • Audio Engine

  


  • CoreAudio

  


  • AudioToolbox

  


  • Audio Unit

  


  


  Which of these should I use to play both network or local music files (flac/wav/mp3/aac/wma/ogg) ? What are their specific roles ?

  


  My understanding is that I should use ffmpeg for demuxing to unpackage, then decode the stream to get PCM samples, possibly using Audio Engine for playback. Is this a software decoding method ? For Apple-supported formats like mp3, can I bypass ffmpeg for decoding ? Which library would be most suitable in this case ?

  


  Additionally, how do I extract metadata (song name, artist, cover, lyrics, etc.) from music files ? Apple's own solutions seem to support only ID3 or iTunes tags. How should I handle other formats like wav/flac ?

  


  The two links below are the resources I've referenced, but they seem outdated. My search for newer, reliable explanations has been fruitless.

  


  

  • whats-the-difference-between-the-apple-audio-frameworks

  


  • Core Audio Essentials

  


  


• ffmpeg : stream copy from .mxf into NLE-compatible format

  9 juin 2013, par David

  Because my NLE software does not support the .mxf-files from Canon XF100 I need to convert them into a supported format.

  As far as I know, mxf-files are just another container format for mpeg2 streams, so it would be really nice to extract the streams and place them into another container (without reencoding).

  I think ffmpeg can do this – correct me if I'm wrong – by running the following command :

  ffmpeg -i in.mxf -vcodec copy out.m2ts (or .ts, .mts, ...)

  ffmpeg finishes without errors after about 2 seconds (in.mxf is abut 170mb) :

  c:\video>c:\ffmpeg\bin\ffmpeg -i in.MXF -vcodec copy out.m2ts
  
  ffmpeg version N-53680-g0ab9362 Copyright (c) 2000-2013 the FFmpeg developers
  
    built on May 30 2013 12:14:03 with gcc 4.7.3 (GCC)
  
    configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
  
  isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
  
  le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
  
  e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --ena
  
  ble-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-l
  
  ibopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libsp
  
  eex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-libvo-
  
  amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --
  
  enable-libxvid --enable-zlib
  
    libavutil      52. 34.100 / 52. 34.100
  
    libavcodec     55. 12.102 / 55. 12.102
  
    libavformat    55.  8.100 / 55.  8.100
  
    libavdevice    55.  2.100 / 55.  2.100
  
    libavfilter     3. 73.100 /  3. 73.100
  
    libswscale      2.  3.100 /  2.  3.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  3.100 / 52.  3.100
  
  Guessed Channel Layout for  Input Stream #0.1 : mono
  
  Guessed Channel Layout for  Input Stream #0.2 : mono
  
  Input #0, mxf, from 'in.MXF':
  
    Metadata:
  
      uid             : 1bb23c97-6205-4800-80a2-e00002244ba7
  
      generation_uid  : 1bb23c97-6205-4800-8122-e00002244ba7
  
      company_name    : CANON
  
      product_name    : XF100
  
      product_version : 1.00
  
      product_uid     : 060e2b34-0401-010d-0e15-005658460100
  
      modification_date: 2013-01-06 11:05:02
  
      timecode        : 01:42:14:22
  
    Duration: 00:00:28.32, start: 0.000000, bitrate: 51811 kb/s
  
      Stream #0:0: Video: mpeg2video (4:2:2), yuv422p, 1920x1080 [SAR 1:1 DAR 16:9
  
  ], 25 fps, 25 tbr, 25 tbn, 50 tbc
  
      Stream #0:1: Audio: pcm_s16le, 48000 Hz, mono, s16, 768 kb/s
  
      Stream #0:2: Audio: pcm_s16le, 48000 Hz, mono, s16, 768 kb/s
  
  Output #0, mpegts, to 'out.m2ts':
  
    Metadata:
  
      uid             : 1bb23c97-6205-4800-80a2-e00002244ba7
  
      generation_uid  : 1bb23c97-6205-4800-8122-e00002244ba7
  
      company_name    : CANON
  
      product_name    : XF100
  
      product_version : 1.00
  
      product_uid     : 060e2b34-0401-010d-0e15-005658460100
  
      modification_date: 2013-01-06 11:05:02
  
      timecode        : 01:42:14:22
  
      encoder         : Lavf55.8.100
  
      Stream #0:0: Video: mpeg2video, yuv422p, 1920x1080 [SAR 1:1 DAR 16:9], q=2-3
  
  1, 25 fps, 90k tbn, 25 tbc
  
      Stream #0:1: Audio: mp2, 48000 Hz, mono, s16, 128 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
    Stream #0:1 -> #0:1 (pcm_s16le -> mp2)
  
  Press [q] to stop, [?] for help
  
  frame=  532 fps=0.0 q=-1.0 size=  143511kB time=00:00:21.25 bitrate=55314.1kbits
  
  frame=  561 fps=435 q=-1.0 size=  151254kB time=00:00:22.42 bitrate=55242.0kbits
  
  frame=  586 fps=314 q=-1.0 size=  158021kB time=00:00:23.41 bitrate=55288.0kbits
  
  frame=  609 fps=255 q=-1.0 size=  164182kB time=00:00:24.34 bitrate=55235.4kbits
  
  frame=  636 fps=217 q=-1.0 size=  171463kB time=00:00:25.42 bitrate=55235.1kbits
  
  frame=  669 fps=194 q=-1.0 size=  180133kB time=00:00:26.72 bitrate=55226.3kbits
  
  frame=  699 fps=173 q=-1.0 size=  188326kB time=00:00:27.92 bitrate=55256.6kbits
  
  frame=  708 fps=169 q=-1.0 Lsize=  190877kB time=00:00:28.30 bitrate=55233.6kbit
  
  s/s
  
  video:172852kB audio:442kB subtitle:0 global headers:0kB muxing overhead 10.1461
  
  18%

  Unfortunately the output file turns out to be displayed correctly only by vlc player.
  My NLE-software (Cyberlink Power Director) is able to open the file but most of the picture is green. Only a few pixels on the left edge show the original video :

  output file

  Any ideas how to solve that problem ? Is there a better way to use .mxf-files in NLE-software without native support ?

  thanks in advance