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• ffmpeg lossless mp4 to image sequence conversion (and back to mp4 again) [closed]

  2 juin 2021, par Cinderella Costallas

  I've browsed google for hours now and cant find anything about this.
I'm really struggling to extract the frames of an mp4 to an image sequence without any quality loss.
I need to be able to convert the image sequence back to an mp4 again also with no quality loss.
My purpose for this is to essentially drop half of all frames, making a 60fps mp4 into 30fps.
Previously the only other way I've found of doing this was to create a rawbitstream which takes up an absurd amount of disk space, and I don't want that. You can find that post here. Anything that can help me achieve this, I would greatly appreciate if you could share it.

  


• 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 ?

  


• Loss voice while re stream with ffmpeg

  20 février 2020, par mehregan

  I’m trying to receive Stream from a VLC and send it to an HLS server.
  But some times (Ex, After one day or some hours) i have No Voice on HLS Server.
  this is the command i use :

  ffmpeg  -nostdin -i rtsp://127.0.0.1:8554/  -vb 600k -maxrate 600k -aspect "852:480" -s "852x480" -c:v libx264 -profile:v "Main" -level "3.1" -preset veryfast -r 30 -keyint_min 50 -x264opts "keyint=50:min-keyint=50:no-scenecut" -c:a copy -f flv rtmp:/HLSSERVER/live2/

  According to This i Added -analyzeduration 1G -probesize 50 But it didnt solve my problem