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• From Python, piping images to FFMPEG process with audio input, "-shortest" flag causes output file to contain only 1 frame of video and entire audio

  7 novembre 2023, par b_yang

  From Python, I run FFMPEG and write images to its stdin via pipe, the FFMPEG process has an audio file as input too. Everything works fine like this :

  


  cmd = ['ffmpeg', '-hide_banner', '-y', '-loglevel', 'error', '-f', 'rawvideo', 
'-pix_fmt', 'bgr24', '-video_size', '720x1280', '-r', '30.0', '-an', '-i', '-',
'-i', 'audio.aac', '-acodec', 'copy', 
'-crf', '14', '-pix_fmt', 'yuv420p', 'output.mp4']
proc = subprocess.Popen(cmd, **popen_params)


  


  Because the audio duration might be longer than the video duration, I added a '-shortest' flag (before '-crf') :

  


  cmd = ['ffmpeg', '-hide_banner', '-y', '-loglevel', 'error', '-f', 'rawvideo', 
'-pix_fmt', 'bgr24', '-video_size', '720x1280', '-r', '30.0', '-an', '-i', '-',
'-i', 'audio.aac', '-acodec', 'copy', 
'-shortest', '-crf', '14', '-pix_fmt', 'yuv420p', 'output.mp4']
proc = subprocess.Popen(cmd, **popen_params)


  


  However, with the '-shortest' flag, the resulting output.mp4 contains the entire audio, but only 1 frame of video data. What is going on here ?

  


• I keep having the message "MovieWriter ffmpeg unavailable ; using Pillow instead." I want to save as MP4 an animation

  6 décembre 2023, par Enrra

  I am doing an animation :

  


  animation = FuncAnimation(fig, update, frames=len(time_values), interval=250, repeat=False)
with a simple frame update function, I want it save it as a MP4 format :

  


  animation.save(f'{save_path}/heat_map.mp4', writer='ffmpeg', fps=10)

  


  I get the error message "MovieWriter ffmpeg unavailable ; using Pillow instead."

  


  I tried to do the following :

  


  plt.rcParams['animation.ffmpeg_path'] ='C:\\ProgramData\\Anaconda3\\LIB\\site-packages\\ffmpeg'
FFwriter = animation.FFMpegWriter()
animation.save(f'{save_path}/heat_map.mp4', writer = FFwriter, fps=10)


  


  This gets me an error message :

  


  Traceback (most recent call last):&#xA;  File "Graph_V1-8.py", line 406, in <module>&#xA;    FFwriter = animation.FFMpegWriter()&#xA;AttributeError: &#x27;FuncAnimation&#x27; object has no attribute &#x27;FFMpegWriter&#x27;&#xA;</module>

  


  and I also tried to do the following :
animation.save(f'{save_path}/heat_map.mp4', writer='ffmpeg', fps=10, codec='libx264')

  


  which also get me the error :
"MovieWriter ffmpeg unavailable ; using Pillow instead."

  


  When I write :

  


  pip install ffmpeg
Requirement already satisfied: ffmpeg in c:\programdata\anaconda3\lib\site-packages (1.4)


  


  Thank you in advance for your help

  


• How to "mimic" -c copy when using filters with ffmpeg ? Is there a built-in feature or I'll need some scripting ? [closed]

  29 décembre 2023, par Fabio Freitas

  I'm aware that any stream ffmpeg processes is decoded before applying any desired changes and then re-encoded, which means the stream in question can't simply be copied with -c copy.

  


  Still, I'm not yet very knowledgeable on dealing with media files. Currently, the single issue I'm addressing is cropping black bars from the sides when 4:3 is encoded as 16:9.

  


  That's fairly simple, and I quickly managed to get it going.

  


  Then I noticed some weird stuff via mediainfo and the explorer's side panel. Stream sizes, bitrates and some other details were different than expected.

  


  ---

  


  That's where -c copy comes in. Over the years, every time I tried to solve this, answers would stop at "-c copy can't be used if the stream will be decoded", which is good enough to stop noobs like me from wasting time.

  


  But since I don't know how to use advanced encoding settings, the -c copy I'm looking for is actually how can I re-encode my processed stream using the same (or most similar) settings used before I decoded it.

  


  Is there such an option in ffmpeg ? Are these settings I'm looking for even obtainable by any means ? And if "no" and "yes", could I use ffprobe to write a script for ffmpeg ?

  


  BTW, I'm on Windows 11, but I have Git's SCM tools available.