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• Change Audio pitch and add blur effect in video using ffmpeg Php

  29 mars 2012, par santosh yadav

  I have a video clip and i want to change Identity of person on Video,

  For That i want to change pitch of audio and add blur effect on video,

  I have use following things for change pitch but it is not provide better result,

  ffmpeg -i w.mpg -vcodec copy -an tmpVideo.mpg
  
  ffmpeg -i w.mpg tmpAudio.wav
  
  rubberband -p 6 tmpAudio.wav tmpAudioRB.wav
  
  ffmpeg -i tmpVideo.mpg -i tmpAudioRB.wav -vcodec copy finalVideow_6.mpg

  Any Better solution for Change pitch and add blur effect,

• aspect ratio is changed using ffmpeg sameq and codec copy

  21 mars 2012, par Vishal Parekh

  i am using ffmpeg to extract clip from mp4 video,

  i tried with "-acodec copy -vcodec copy" and "-sameq"

  in both, aspect ration of generated file is changed.

  (
  ffmpeg -sameq -i "input file" "output file"

   ffmpeg -i "input file" -acodec copy -vcodec copy "outputfile"

  )

  source file is of aspect ratio
  sar=4:3
  dar=4:3

  new file is has aspect ratio
  sar=4:3
  dar=1:1

  please help me to solve this problem,

  one weird thing is when i see details in another video tool, it shows me
  sar=4:3
  dar=4:3
  of source video

  but when i use command ffmpeg -i sourcefile, it shows me
  sar=300:400
  dar=1:1

  thanks

• h264 lossless coding

  29 septembre 2014, par cloudraven

  Is it possible to do completely lossless encoding in h264 ? By lossless, I mean that if I feed it a series of frames and encode them, and then if I extract all the frames from the encoded video, I will get the exact same frames as in the input, pixel by pixel, frame by frame. Is that actually possible ?
  Take this example :

  I generate a bunch of frames, then I encode the image sequence to an uncompressed AVI (with something like virtualdub), I then apply lossless h264 (the help files claim that setting —qp 0 makes lossless compression, but I am not sure if that means that there is no loss at any point of the process or that just the quantization is lossless). I can then extract the frames from the resulting h264 video with something like mplayer.

  I tried with Handbrake first, but it turns out it doesn’t support lossless encoding. I tried x264 but it crashes. It may be because my source AVI file is in RGB colorspace instead of YV12. I don’t know how to feed a series of YV12 bitmaps and in what format to x264 anyway, so I cannot even try.

  In summary what I want to know if that is there a way to go from

  Series of lossless bitmaps (in any colorspace) -> some transformation -> h264 encode -> h264 decode -> some transformation -> the original series of lossless bitmaps

  If there a way to achieve this ?

  EDIT : There is a VERY valid point about lossless H264 not making too much sense. I am well aware that there is no way I could tell (with just my eyes) the difference between and uncompressed clip and another compressed at a high rate in H264, but I don’t think it is not without uses. For example, it may be useful for storing video for editing without taking huge amounts of space and not losing quality and spending too much encoding time every time the file is saved.

  UPDATE 2 : Now x264 doesn’t crash. I can use as sources either avisynth or lossless yv12 lagarith (to avoid the colorspace compression warning). Howerver, even with —qp 0 and a rgb or yv12 source I still get some differences, minimal but present. This is troubling, because all the information I have found on lossless predictive coding (—qp 0) claims that the whole encoding should be lossless, but I am unable to verifiy this.