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• ffmpeg library rotates video after compression Android

  14 septembre 2016, par Leo Wiki

  I’m using ffmpeg library for video file compression in my Android project.

  To implement ffmpeg I refereed this link. Compression is working fine but after compression process this library rotating my video 90 degree which I don’t want to be happen. I googled a lot but yet not reach to solution which can tell me how to stop rotating the video. For video compression I’m using the following command—

  ffmpeg -y -i /sdcard/videokit/in.mp4 -strict experimental -vf transpose=1 -s 160x120 -r 30 -aspect 4:3 -ab 48000 -ac 2 -ar 22050 -b 2097k /sdcard/videokit/out.mp4

  Please let me know if I can provide more information to you.

  Thank you.

• Playback : audio-video synchronization algorithm

  7 août 2016, par Rick77

  I’m in the process of creating a very basic video player with the ffmpeg libraries and I have all the decoding and re-encoding in place, but I’m stuck on audio video synchronization.

  My problem is, movies have audio and video streams muxed (intertwined) in a way that audio and video comes in "bursts" (a number of audio packets, followed by juxtaposed video frames), like this, where each packet has its own timestamp :

  A A A A A A A A V V V V A A A A A A A V V V V ...
  
  
  
  A: decoded and re-encoded audio data chunk
  
  V: decoded and re-encoded video frame

  supposedly in a way to prevent too much audio to be processed without video, and the other way around.

  Now I have to decode the "bursts" and send them to the audio/video playing components in a timely fashion, and I am a bit lost in the details.

  1. is there a "standard" strategy/paradigm/pattern to face this kind of problems ?
  2. are there tutorials/documentation/books around explaining the techniques to use ?
  3. how far can the muxing go in a well coded movie ?

  Because I don’t expect anything like this :

  AAAAAAAAAAA .... AAAAAAAAAAAAA x10000 VVVVVVVVVVVVVV x1000
  
  audio for the whole clip followed by video

  or this :

  VVVVVVVVVVVV x1000 AAAAAAAAAAA...AAAAAAAAA x1000    
  
  all video frames followed by the audio

  to happen in a well encoded video (after all, preventing such extremes is what muxing is all about...)

  Thanks !

  UPDATE : since my description might have been unclear, the issue is not with how the streams are, or about how to decode them : the whole audio/video demuxing, decoding, rescaling and re-encoding is set and sound, and each chunk of data has its own timestamp.

  My problem is what to do with the decoded data without incurring in buffer overrun and underrun and, generally, clogging my pipeline, so I guess it might be considered a "scheduling" problem.

• FFMPEG rotation issue [closed]

  28 février 2024, par pigfox

  I am trying to rotate a video using ffmpeg, the command I'm running is

  


  ffmpeg -i video.mp4 -vf "transpose=1" -acodec copy video.out.mp4


  


  The problem is that the processed video is rotated 180 degrees clockwise.
I need a 90 degree rotation.
According to some docs I found the flags are as follows.

  


  #0 – means rotate by 90 degrees counterclockwise and flip
#1 – means rotate by 90 degrees clockwise
#2 – means rotate by 90 degrees counterclockwise
#3 – means rotate by 90 degrees clockwise and flip


  


  Any idea how to rotate the video 90 degrees clockwise ?