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• avformat/id3v2 : Don't reverse the order of id3v2 APICs

  13 avril 2021, par Andreas Rheinhardt

  avformat/id3v2 : Don't reverse the order of id3v2 APICs
  When parsing ID3v2 tags, special (non-text) metadata is not applied
  
  directly and unconditionally ; instead it is stored in a linked list
  
  in which elements are prepended. When traversing the list to add APICs
  
  (or private tags) at the end, the order is reversed. The same also
  
  happens for chapters and therefore the chapter parsing code already
  
  reverses the chapters.
  This commit changes this : By keeping pointers to both head and tail
  
  of the linked list one can preserve the order of the entries and
  
  remove the reordering code for chapters. Only the pointer to head
  
  will be exported : No current caller uses a nonempty list, so exporting
  
  both head and tail is unnecessary. This removes the functionality
  
  to combine the lists of special metadata read from different ID3v2 tags,
  
  but that doesn't make really much sense anyway (and would be trivial
  
  to implement if desired) and allows to remove the now unnecessary
  
  initializations performed by the callers.
  The FATE-reference for the id3v2-priv test had to be updated
  
  because the order of the tags read into the dict is reversed ;
  
  for id3v2-priv-remux only the md5 and not the ffprobe output
  
  of the remuxed file changes because the order of the private tags
  
  has up until now been reversed twice.
  The references for the aiff/mp3 cover-art tests needed to be updated,
  
  because the order of the attached pics is reversed upon reading.
  
  It is still not correct, because the muxers write the pics in the order
  
  in which they arrive at the muxer instead of the order given by
  
  pkt->stream_index.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavformat/aacdec.c
  • [DH] libavformat/aiffdec.c
  • [DH] libavformat/asf.c
  • [DH] libavformat/dsfdec.c
  • [DH] libavformat/id3v2.c
  • [DH] libavformat/id3v2.h
  • [DH] libavformat/iff.c
  • [DH] libavformat/omadec.c
  • [DH] libavformat/wavdec.c
  • [DH] tests/ref/fate/cover-art-aiff-id3v2-remux
  • [DH] tests/ref/fate/cover-art-mp3-id3v2-remux
  • [DH] tests/ref/fate/id3v2-priv
  • [DH] tests/ref/fate/id3v2-priv-remux

• Using FFMpeg with Asp .Net Core and video stream

  15 août 2022, par Gaetano Lenoci

  I'm implementing an API that allows the user to send a video stream and generate thumbnails. I'm using asp.net core and Azure Blob Storage. The interface of API is this :

  


      [HttpPost]
    [Route("test_upload")]
    public IActionResult TestUpload( IFormFile mediaFile ) {
        //->store mediaFile
        //->generate thumbnail
        //->save thumbnail
        return Ok();
    }


  


  I need to do two main things :

  


  

  1. Generate a thumbnail

  


  2. Get video information such as the duration

  


  


  I tried to use libraries from Nuget, but all of this needs the file path and I don't have the file path, just the video Stream or the Blob from the Blob Storage after saving. So, my question is, how can I manage video directly from the stream using FFmpeg or another tool ?

  


  I know Azure Media Services provide a lot of tools to manage media files such as videos and audio, but it's too slow for videos that are just 2Mb and 30 seconds long. And I don't need to encode the video, create streams or other things like that. I just need to take video information from a Stream and store the video on the Storage.

  


  Any idea ? Thanks !

  


  Update 1 :
I wrote a workaround by creating a folder for temporary videos, I just save the video in this folder, create the thumbnail and delete the temp file. But I don't know if this practice has some bad side effects.

  


• Export frames/images from compressed video

  24 mars 2015, par Jan Viehweger

  I have a compressed movie (mp4) and I want to extract every single frame / image from it. I know that each individual frame of the video only contains the changed pixels regarding to the last keyframe, because of the video compression. But that is exactly what I want. I just want to see those differences. I want to visualy see how the compressor works.

  Is there some tool like imagemagick out there what can things like that ?