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• ffmpeg inconsistent speed results by version breaking large audio file into multiple pieces with -ss/-to positional parameters [closed]

  2 novembre 2024, par BenH

  I am trying to chop a large (12 hour+) audio file up into multiple segments using multiple -ss/-to positional operations.

  


  ffmpeg.exe -loglevel error -stats -i "C:\data\chapters\joined_output.mp3" -ss -1 -to 1159 -c copy "C:\data\chapters\001 - Chapter 1.mp3" -ss 1159 -to 1800 -c copy "C:\data\chapters\002 - Chapter 2.mp3" -ss 1800 -to 3181 -c copy "C:\data\chapters\003 - Chapter 3.mp3" ... output.mp3


  


  The '...' indicates that I have more than 20 of such repeated statements to break up into 20 or more chapter files.

  


  I arrived on this because using individual command were processing the entire file each time to parse out the section I wanted. I realize there is an option to place -ss/-to prior to the input file, and have since discovered that this appears to work quicker, but I have not found syntax to use this in a single command and therefore must create a separate command for each chapter.

  


  The above syntax appears to work fine, but was taking about 4 minutes to process. When I reverted to older versions this operation completes much quicker. About 20 seconds with version 6.1 and about 10 seconds on version 5.

  


  There is some discrepancy with how the old versions report the length of the file (it appears to show only about 6.5 hours processed in "out_time" value), but the resulting output files appear to be correct. I think it might be reporting out_time of only the longest section it is processing as the 6.5 hours appear to match the length of that output section.

  


  To be clear, version 5 using my above syntax appears to create all my output files correctly in 10 seconds.

  


  If I split them up into individual commands with -ss/-to before the input, then it actually takes longer with ffmpeg version 5/6 (about 45 seconds compared to 10-20 seconds).
With the latest version 7 it takes about 1 min, 15 secs. Much better than the 4 minutes using my syntax above but still well slower than using version 5/6 with that same syntax.

  


  So, in short, why am I able to (apparently) properly split this 12 hour file into about 25 different segments in about 10 seconds using the syntax above on version 5, but it takes 2x that long on 6, and 30x that long on 7 ? I assume there are just syntax changes I can't figure out or some changes to default behavior ?

  


• Revision 085f76e535 : Add experimental VBR adaptation method. Add code to monitor over and under spen

  15 avril 2014, par Paul Wilkins

  Changed Paths :
   Modify /vp9/encoder/vp9_firstpass.c

  
   Modify /vp9/encoder/vp9_onyx_if.c

  
   Modify /vp9/encoder/vp9_ratectrl.c

  
   Modify /vp9/encoder/vp9_ratectrl.h

  
  
  Add experimental VBR adaptation method.

  Add code to monitor over and under spend and
  apply limited correction to the data rate of subsequent
  frames. To prevent the problem of starvation or overspend
  on individual frames (especially near the end of a clip) the
  maximum adjustment on a single frame is limited to a %
  of its un-modified allocation.

  Change-Id : I6e1ca035ab8afb0c98eac4392115d0752d9cbd7f

• ffmpeg-next how can I enable multithreading on a decoder ?

  14 décembre 2022, par Brandon Piña

  I'm using the rust crate ffmpeg-next to decode some video into individual frames for usage in another library. Problem is when I run my test it only seems to use a single core. I've tried modifying the threading configuration for my decoder as you can see below, but It doesn't seem to be do anything

  


          let context_decoder =
            ffmpeg_next::codec::context::Context::from_parameters(input_stream.parameters())?;
        let mut decoder = context_decoder.decoder().video()?;
        let mut threading_config = decoder.threading();
        threading_config.count = num_cpus::get();
        threading_config.kind = ThreadingType::Frame;

        decoder.set_threading(threading_config);