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• How to efficiently create H264 mpeg from two clips with known different motion intensity ?

  14 février 2017, par Serge

  Given an audio and an image we create a static image "video" and then append a short clip that has a rather intense motion.

  Audio and image varies from run to run. Appended animation is always the same. Rendering is done with ffmpeg on a remote server. Rendered file must be in h264 codec mpg.

  Speed of encoding is crucial. Is there a fast and effective way to generate and merge the two clips quickly ?

  Atm we use the following ffmpeg commands :

  // create first clip from image
  
  ffmpeg -loop 1 -r 24 -i $IMAGE -i $AUDIO -t $AUDIO_LENGTH -c:a aac -profile:a aac_low -ar 48000 -b:a 192k -bsf:a aac_adtstoasc -strict -2 -y -c:v libx264 -profile:v high -preset veryfast  -tune stillimage -crf 24 -x264opts bframes=2 -pix_fmt yuv420p -safe 0  clip1.mpg
  
  // . . .
  
  // then append the animation
  
  ffmpeg -f concat -safe 0 -i list.txt -c copy -y -safe 0 final.mpg 

  Intuition is that we can benefit form knowing exact timing of a first clip with a static image and the second one with intense animation – like it is determined in the 1-st pass of a 2-pass compression.

  Someone experienced in tech of h264 codec and mpeg please advice.

• ffmpeg multiple pipes with different filters and outputs

  3 janvier 2024, par diegoddox

  I'm trying to pipe multiple outputs to an s3 but so far it's only working if I tried with only one pipe as soon as I add more I get Could not write header (incorrect codec parameters ?): Broken pipe error.

  


  aws s3 cp s3://bucket-name/original.mp4 - | \
  ffmpeg -f mp4 -i pipe:0 \
  -vf "scale=1280x720:flags=lanczos" -c:a aac -b:a 96k -movflags frag_keyframe+empty_moov -f mp4 pipe:1 | aws s3 cp - s3://bucket-name/720.mp4 --region my-region \
  -vf "scale=854x480:flags=lanczos" -c:a aac -b:a 96k -movflags frag_keyframe+empty_moov -f mp4 pipe:2 | aws s3 cp - s3://bucket-name/480.mp4 --region my-region \
  -vf "scale=640x360:flags=lanczos" -c:a aac -b:a 96k -movflags frag_keyframe+empty_moov -f mp4 pipe:3 | aws s3 cp - s3://bucket-name/360.mp4 --region my-region \
  -ss 00:00:00 -t 3 -vf "fps=10,scale=720:-1" -movflags frag_keyframe+empty_moov -f gif pipe:4 | aws s3 cp - s3://bucket-name/thumbnail.gif --region my-region


  


  Thanks in advance

  


• How do I play back video on Android with custom playback speed ?

  13 novembre 2015, par guidow

  I want to play back a video in Android, rendering it to a SurfaceTexture or something else that is usable as an OpenGL ES texture, but I need very precise control over the playback speed of the video to synchronize it to a stream of external events. These events will happen at a roughly predictable speed, but the exact speed will depend on many small mechanical details, influenced by many small factors, including the weather (and possibly even the phase of the moon...).

  The android.media.MediaPlayer class provided by android allows rendering to a SurfaceTexture (and the 360Videos app from the Oculus Mobile SDK successfully uses that feature), but unfortunately does not seem to allow altering the playback speed, at least not as far as I could tell from the documentation here.

  I have tried pausing and resuming the playback using pause() and start() respectively, to influence the playback speed, but that leads to extremely choppy and slow playback. My idea here was to make the video have a higher framerate than would ever be needed, and to then manually retard every frame until it actually needs to be shown. From the messages in the log, it looks to me like the MediaPlayer class will release various needed resources on pause and rerequest them on resume, which obviously kills performance if you do that once per frame.

  Another option I am looking at is ffmpeg. This one seems like it will do what i want, it doesn’t do any timings itself, it just decodes frames whenever I tell it to to a buffer, leaving me to use it however I want, whenever I want. The obvious drawback is that ffmpeg, at least on android, doesn’t do hardware decoding and probably won’t be able to decode 4K media in realtime.

  Yet another thing I was looking at was OpenMAX AL. Unfortunately, OpenMax AL is pretty hard to get into. I haven’t found any good beginner’s documentation yet, only some old, maybe outdated, READMEs as well as the interface specification from Khronos. The latter is a very long and cumbersome read, though, and I couldn’t yet even figure out if OpenMAX AL will even allow me to do my own timings...