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• avformat/rtsp : Fix timeout option

  30 mai 2021, par Andriy Gelman

  avformat/rtsp : Fix timeout option
  92c40ef882be115e72d2aa02f9032b7ce88f8537 added a listen_timeout option
  
  for sdp. This allowed a user to set variable timeout which was
  
  originally hard coded to 10 seconds.
  The commit used the initial_timeout variable to store the value. But
  
  this variable is shared with rtsp where it's used to infer a "listen"
  
  mode. Thus, the timeout value could not be set in rtsp, and the default
  
  value (initial_timeout = -1) would give 100ms timeout.
  This was attempted to be fixed in c8101aabee654f6d147a4d89f77fa73e18908610,
  
  which changed the meaning of initial_timeout = -1 to be an infinite
  
  timeout. However, it did not address the issue that the timeout could
  
  still not be set. Being able to set the timeout is useful because it
  
  allows to automatically reconfigure from a udp to tcp connection in the
  
  lower transport.
  In this commit this is fixed by using the stimeout variable to
  
  store the timeout value.
  Signed-off-by : Andriy Gelman <andriy.gelman@gmail.com>
  

  • [DH] libavformat/rtsp.c
  • [DH] libavformat/rtsp.h

• hevc : deobfuscate slice/tile boundary handling for DBF

  27 juillet 2014, par Anton Khirnov

  hevc : deobfuscate slice/tile boundary handling for DBF
  Use named constants instead of magic numbers, avoid using variables with
  
  inverse meaning from what their name implies.
  

  • [DH] libavcodec/hevc.c
  • [DH] libavcodec/hevc.h
  • [DH] libavcodec/hevc_filter.c

• Lossless compression of a sequence of similar grayscale images

  25 octobre 2020, par damien200

  I would like to have the best compression ratio of a sequence of similar grayscale images. I note that I need an absolute lossless solution (meaning I should be able to check it with an hash algorithm).

  


  What I tried

  


  I had the idea to convert my images into a video because there is a chronology between images. The encoding algorithm would compress using the fact that not all the scene change between 2 pictures. So I tried using ffmpeg but I had several problems due to sRGB -> YUV colorspace compression. I didn't understand all the thing but it's seems like a nightmare.

  


  Example of code used :

  


  ffmpeg -i %04d.png -c:v libx265 -crf 0 video.mp4 #To convert into video
ffmpeg -i video.mp4 %04d.png #To recover images



  


  My second idea was to do it by hand with imagemagik. So I took the first image as reference and create a new image that is the difference between image1 and image2. Then I tried to add the difference image with the image 1 (trying to recover image 2) but it didn't work. Noticing the size of the recreated picture, it's clear that the image is not the same. I think there was an unwanted compression during the process.

  


  Example of code used :

  


  composite -compose difference 0001.png 0002.png diff.png #To create the diff image
composite -compose difference 0001.png diff.png recover.png #To recover image 2


  


  Do you have any idea about my problem ?
And why I don't manage to do the perfect recover with iamgemagik ?

  


  Thanks ;)

  


  Here are 20 samples images : https://cloud.damien.gdn/d/f1a7954a557441989432/