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• avformat/flacenc : Only update streaminfo if it has changed

  12 avril 2020, par Andreas Rheinhardt

  avformat/flacenc : Only update streaminfo if it has changed
  An AVStream's codecpar is supposed to be filled by the caller before
  
  avformat_write_header() ; if the CodecParameters change, the caller
  
  should signal this via packet side data, but not touch the AVStream's
  
  codecpar.
  The FLAC muxer checks for packet side data containing updated extradata,
  
  yet if nothing has arrived by the time the trailer is written, the
  
  already written extradata is overwritten by the very same extradata
  
  again, unless the output is unseekable, in which case a warning that the
  
  FLAC header can't be rewritten is emitted.
  This commit changes this by only trying to rewrite the extradata if a
  
  new streaminfo arrived via packet side data. Only then is a warning
  
  emitted in case the output is unseekable.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/flacenc.c

• hevcdec : properly export some side data with frame threading

  29 juin 2017, par wm4

  hevcdec : properly export some side data with frame threading
  I noticed this with mastering display data. If frame threading is
  
  enabled, this side data is exported only for some frames. It turns out
  
  it's not properly propagated to the worker threads.
  I didn't touch A53 captions, because that involves memory allocation and
  
  freeing the data as side data is exported.
  Micro bump so that API users can detect the bug fix.
  

  • [DH] libavcodec/hevcdec.c
  • [DH] libavcodec/version.h

• ffmpeg - How to resize frame collage (grid of images) to grid of different dimensions, while respecting frame order ?

  12 mars 2023, par JamesK

  I have an input of a "frame collage" (that is, frames extracted from a video, arranged in a certain grid). I want to rearrange the frames from a collage into a different grid shape. I can calculate the input coordinates (or bounds, e.g. x.min -> x.max, y.min -> y.max) and output coordinates for each frame. Basically, I want to resize a grid, while respecting the positioning of each element of the original grid.

  


  As an example, given a frame collage that is 9x2 (9 columns wide, 2 rows tall), with image resolution of 1080x240 (width x height), resize the frame collage to be 6x3 (6 columns wide, 3 columns tall), with an image resolution of 720x480 (width x height), while respecting the order of the frames in the input image (left to right, top to bottom).

  


  I generated the frame mappings (where the original frame was located, and where the new frame should be placed) for each frame, a table of that data is available here : https://pastebin.com/raw/a5UhKhek (posted on pastebin because discord would murder the formatting).

  


  Does anyone have any ideas on how I might be able to pull this off ?

  


  I've investigated the tile and untile filter, as well as looked into the select filter, although the syntax for the lattermost is a touch confusing to me.