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• ffmpeg Split And Zoom

  4 décembre 2019, par megaimd mega

  ffmpeg -i video.mp4 -c:v libx264 -crf 22 -map 0 -segment_time 3 -reset_timestamps 1 -g 10 -sc_threshold 0 -force_key_frames “expr:gte(t,n_forced*3)” -f segment out/output%03d.mp4

  As you can see, it is saved :

     output1.mp4
  
     output2.mp4
  
     output3.mp4
  
     output4.mp4

  and so on, it split every 3 seconds.
  Ho can I make, for exemple

     output1.mp4 zoom 2X
  
     output2.mp4 Normal
  
     output3.mp4 zoom 2X
  
     output4.mp4 Normal

  for one movie to zoom in and for another to not zoom

• Which decoder does ffmpeg actually use ? [closed]

  8 décembre 2024, par LTR

  How can I get ffmpeg to show exactly which decoder it uses ?

  


  Example 1

  


  In this example, I request Intel QuickSync decoding. However, QuickSync is not available because it's running on an AMD CPU. ffmpeg seems to fall back to CPU decoding, but doesn't say anything about that :

  


  > ffmpeg -hwaccel qsv -i "file.mp4" -f null -
...
(nothing in the output refers to choice of decoder)


  


  Example 2

  


  In this example, we request "auto" hardware acceleration.

  


  > ffmpeg -hwaccel auto -i "file.mp4" -f null -
...
[h264 @ 000001ed37d7a040] Using auto hwaccel type dxva2 with new default device.


  


  Ffmpeg says that it uses the DXVA2 API with the default device. This is better than nothing, but it would be helpful if it said the name of the device chosen.

  


  How can I instruct ffmpeg to always output this information ? I tried "-v verbose" but did not find anything in the output regarding the choice of decoder.

  


  Related : How do I know if ffmpeg is using a hardware decoder ?

  


• Fallback input for ffmpeg

  22 septembre 2018, par Daniel Cantarin

  I’m doing some transcoding from a third-party remote input stream that I do not control.

  This input stream has errors from time to time, that I would like to mitigate before sending the stream to my transcoding pipeline, avoiding this way some possible problems in the output.

  I have several ideas regarding different problems. But the most basic scenario I would like to set up is as follows : when the stream is down, or it somehow loses some frames, I want to fill that video gap with a secondary input (like a blank screen, for example).

  For this simple task, I would like to use ffmpeg. I know it can mix, let’s say, an input stream with a fullscreen black square static image. However, I have to deal with this other condition : ffmpeg would run in the same infraestructure for the actual transcoding pipeline. That infraestructure must use its computing power for rendering the output. So, whatever ffmpeg command I end up using should use the minimum possible computing power.

  My actual problem : if I use -vcodec copy, in order to use minimum CPU, I can’t alter the original stream. But if I alter the original stream (by mixing it with some other stream), the operation uses CPU.

  My question : Is there a way to use -vcodec copy, but with a fallback input (instead of a mixed one) for when there are video gaps in the primary stream ?

  Thanks in advance.