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• How to losslessly compress a sequence of slowly-changing images into a video ?

  26 juillet 2023, par Claude C

  I have a sequence of jpeg images captured like a timelapse, with the same dimension and changing slowly in order. I want to compress the size of the whole sequence while still able to recover each individual image with their raw pixel information unchanged.

  


  I googled and found that a possible solution is to compress it into a video, which exploits the strong temporal correlation (inter-frame redundancy) between consecutive frames, as suggested here. I tried ffmpeg libx264 but none of the option combinations seem to preserve frame quality and compress total size at the same time (-crf 0 keeps the quality but the size of the video is even larger than the input sequence).

  


  So my questions is,

  


  

  • What is the correct way to losslessly compress a sequence of slowly-changing images ?

  


  


  I can accept using softwares other than ffmpeg (as long as it is on windows or linux), doing color space conversion on raw images (if necessary). It is OK if a the compression is done without converting to videos. Thank you.

  


• avfilter/vf_unsharp : Don't dereference NULL

  1er décembre 2019, par Andreas Rheinhardt

  avfilter/vf_unsharp : Don't dereference NULL
  The unsharp filter uses an array of arrays of uint32_t, each of which is
  
  separately allocated. These arrays also need to freed separately ; but
  
  before doing so, one needs to check whether the array of arrays has
  
  actually been allocated, otherwise one would dereference a NULL pointer.
  
  This fixes #8408.
  Furthermore, the array of arrays needs to be zero-initialized so that
  
  no uninitialized pointer will be freed in case an allocation of one of
  
  the individual arrays fails.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavfilter/vf_unsharp.c

• RuntimeException on FFmpegMediaMetaDataRetriever setDataSource (status = 0xFFFFFFFF)

  27 septembre 2017, par LaVieEnRoux

  I am attempting to load a .mp4 video from assets. I am getting the following error at the top of the stack trace if I access either via URI or FileDescriptor :

  java.lang.RuntimeException : setDataSource failed : status = 0xFFFFFFFF
  at wseemann.media.FFmpegMediaMetadataRetriever.setDataSource(Native
  Method)

  A little snippet of code that causes the exception :

  mmr = new FFmpegMediaMetadataRetriever();
  
  AssetManager assets = getAssets();
  
  AssetFileDescriptor afd = assets.openFd(TEST_VIDEO);
  
  mmr.setDataSource(afd.getFileDescriptor(), afd.getStartOffset(), afd.getLength());

  I’m using version 1.0.14 in Android Studio. I’ve tried using either the pre-built AAR or the compile ’com.github.wseemann:FFmpegMediaMetadataRetriever:1.0.14’ link in the build.gradle dependences, and both give the same result.

  The curious thing is that this loads perfectly fine when I use MediaMetadataRetriever on the same video in place of FFmpegMediaMetadataRetriever. One of the videos with which the error was happening is available at the following link : https://drive.google.com/open?id=0B_r_uzvCTCgsS2xVMUk4TW13YUE

  Anyone have suggestions ? I’d be using MediaMetadataRetriever instead but I need to be able to grab every individual frame of the video and it doesn’t appear to be capable.