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• Copying avcodec parameters

  4 juin 2020, par Ayxan

  I am trying to use libav to convert an MP4 file to an MP3 file. Basically trying to achieve what ffmpeg -i filename.mp4 filename.mp3 does. I've found this official example. But when I run it with an input MP4 and an output MP3 I get an error :

  



  


  Invalid audio stream. Exactly one MP3 audio stream is required.

  


  



  I am not at all familiar with this library but I think I have narrowed the problem down to this line :

  



  ret = avcodec_parameters_copy(out_stream->codecpar, in_codecpar);


  



  It seems to copy all streams for a video file but we only need one for the MP3 file ? I am not sure. There doesn't seem to be a function to copy only the parameters relevant to audio. I checked the sources, avcodec_parameters_copy does a simple memcpy.

  



  Questions :

  



  

  1. Is this the actual problem ?

  


  2. How do I solve it ?

  


  3. Am I on the right track to achieve the goal of extracting audio from a video file ? I've seen this question (and other similar questions like this and this) on here but none seem to have a complete code example. The C API documentation for this library is also a little lacking.

  


  


• using ffmpeg from macOS terminal for uploading youtube short from android just do nothing

  25 juin 2023, par Yogi Arif Widodo

  my component / recording is using blachole plugin on macOS.

  


  engine : 13" Macbook Pro M1 ( macOS 13.2 / Ventura )

  


  step to reproduce

  


  

  1. my output is screenRecordingAudio ( this name is custom name ).

  


  


  // screenRecordingAudio in audioMidi : 
BlackHole 16ch [mark as checked on use]
External Headphones [mark as checked on use]


  


  


  screenRecordingAudio is using on by click on right top of bar UI, click sound, click screenRecordingAudio.

  


  


  OR

  


  


  screenRecordingAudio is using on Settings ➡️ Sounds ➡️ Output ➡️ then choose screenRecordingAudio

  


  


  

  2. my input is quickTimeInput ( this name is custom name ).

  


  


  // quickTimeInput in audioMidi : 
BlackHole 16ch [mark as checked on use]


  


  

  3. then using ⌘ + shift + 5 , on option i use quickTimeInput

  


  4. i use these command to convert into mp4 and also purpose to get more small size video

  


  


  #!/bin/bash

# greet the user
function yoVideo() {
  ffmpeg -i $1.mov -c:v libx264 -preset medium -crf 23 -c:a aac -b:a 128k -movflags +faststart $1.mp4
}


  


  OR

  


  ffmpeg -i yogiarifwidodo.mov -c:v libx264 -preset medium -crf 23 -c:a aac -b:a 128k -movflags +faststart yogiarifwidodo.mp4


  


  

  5. then i move the video into my phone android.

  


  6. then when i tried to upload on youtube as short, its cannot be process to upload ( its just do nothing ) but when i upload on facebook reels its work also on instagram story its still working also for whatsapp story.

  


  


  when i didnt convert into mp4 its also happend and in any other case for example whatsapp story , its lagging to review video before upload . its happend to on instagram .
but when i force upload , the result video is good and smooth . then i re download my video its still best video and when try to upload my download video , there is no lagging in any condition.

  


  how to get ffmpeg perform into mp4 and also no lagging on editing while uploading at whatsapp story or instagram story or facebook , etc ?
by the way i dont know command ffmpeg , the code is copied from stackoverflow and i forgot where is it.

  


• FFmpeg is using more threads than I expect when using -threads

  7 décembre 2016, par Tom Peters

  The number of actual threads used by FFmpeg do not line up with the number I pass using the -threads argument.

  I’ve run tests on both my MacBook Air, which has 4 cores, and a VM I have which has 2 cores. The number of threads used are consistent across both machines.

  Using a single thread returns what I would expect : 1 thread is used.

  $ ffmpeg -threads 1 -i clip.mp4 -threads 1 -acodec libfdk_aac -vcodec libx264 -b:v 200k -vf scale=200:-2 -y clip-200.mp4
  
  
  
  $ cat /proc/$(pgrep ffmpeg)/status | grep Threads
  
  Threads:        1

  If I set the -threads option on the input, it increase the number of threads used to 3. This somewhat makes sense to me since the input would use 2 threads and the output would use a single thread.

  $ ffmpeg -threads 2 -i clip.mp4 -threads 1 -acodec libfdk_aac -vcodec libx264 -b:v 200k -vf scale=200:-2 -y clip-200.mp4
  
  
  
  $ cat /proc/$(pgrep ffmpeg)/status | grep Threads
  
  Threads:        3

  This is where I start to get confused. If instead, I leave the input -threads at 1 and set the output -threads to 2, it uses 8 threads (not 3 like I would expect).

  $ ffmpeg -threads 1 -i clip.mp4 -threads 2 -acodec libfdk_aac -vcodec libx264 -b:v 200k -vf scale=200:-2 -y clip-200.mp4
  
  
  
  cat /proc/$(pgrep ffmpeg)/status | grep Threads
  
  Threads:        8

  If I add a second output with -threads 1, it does not increase the number of threads used.

  $ ffmpeg -threads 1 -i clip.mp4 -threads 2 -acodec libfdk_aac -vcodec libx264 -b:v 200k -vf scale=200:-2 -y clip-200.mp4 \
  
                                  -threads 1 -acodec libfdk_aac -vcodec libx264 -b:v 250k -vf scale=250:-2 -y clip-250.mp4
  
  
  
  cat /proc/$(pgrep ffmpeg)/status | grep Threads
  
  Threads:        8

  However, if the second output also specifies two threads, the thread count jumps to 15.

  $ ffmpeg -threads 1 -i clip.mp4 -threads 2 -acodec libfdk_aac -vcodec libx264 -b:v 200k -vf scale=200:-2 -y clip-200.mp4 \
  
                                  -threads 2 -acodec libfdk_aac -vcodec libx264 -b:v 250k -vf scale=250:-2 -y clip-250.mp4
  
  
  
  cat /proc/$(pgrep ffmpeg)/status | grep Threads
  
  Threads:        15

  Every incremental bump beyond -threads 2 will use an additional 3 threads (e.g. threads 2 uses 8, threads 3 uses 11, threads 4 uses 14.

  So it seems like anytime you use -threads 2 the formula is something like :

  1 + [ (1 + (3 * output_n_threads)) + ... ]

  Ultimately my question is why do the number of actual threads used wildly differ from the options I’m specifying.

  Thanks.