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• avformat/matroskadec : Improve invalid length error handling

  17 mai 2019, par Andreas Rheinhardt

  avformat/matroskadec : Improve invalid length error handling
  1. Up until now, the error message for EBML numbers whose length exceeds
  
  the limits imposed upon them because of the element's type did not
  
  distinguish between known-length and unknown-length elements. As a
  
  consequence, the numerical value of the define constant
  
  EBML_UNKNOWN_LENGTH was emitted as part of the error message which is
  
  of course not appropriate. This commit changes this by adding error
  
  messages designed for unknown-length elements.
  2. We impose some (arbitrary) sanity checks on the lengths of certain
  
  element types ; these checks were conducted before the checks depending
  
  on whether the element exceeds its containing master element. Now the
  
  order has been reversed, because a failure at the (formerly) latter
  
  check implies that the file is truly erroneous and not only fails our
  
  arbitrary length limit. Moreover, this increases the informativeness of
  
  the error messages.
  3. Furthermore, the error message in general has been changed by replacing
  
  the type of the element (something internal to this demuxer and
  
  therefore suitable as debug output at best, not as an error message
  
  intended for ordinary users) with the element ID. The element's position
  
  has been added, too.
  4. Finally, the length limit for EBML_NONE elements has been changed so
  
  that all unknown-length elements of EBML_NONE-type trigger an error.
  
  This is done because unknown-length elements can't be skipped and need
  
  to be parsed, but there is no syntax to parse available for EBML_NONE
  
  elements. This is done in preparation for a further patch which allows
  
  more unknown-length elements than just clusters and segments.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskadec.c

• Is it possible to fetch some key-frames of a video by using the HTTP Range header

  9 décembre 2020, par pvd

  I've read the SO problem , and it seems not applying to my specific case.

  


  Is it possible to fetch some key-frames of a video from web server by the HTTP Range header ? For example, for a 30 seconds duration video, we'd like to analysis the I-frame around 00:00:02, 00:00:15, 00:00:28.

  


  I need to analysis the videos from internal web server to detect if there's specific watermarks in it and some other analysis.

  


  Since the first I-frame might be invalid sometimes(Logo for example), we were planning to extract the I-frame from the 00:00:02, the middle I-frame, and the last 2nd second I-frame.

  


  For example, for a 30 seconds duration video, we'd like to analysis the I-frame around 00:00:02, 00:00:15, 00:00:28.

  


  We could make it works while download the whole video, since most of the data we downloaded from the server are not being used. I was wondering if maybe we could only use the HTTP Range header to download partial data and analysis it ?

  


• swscale/utils : override forced-zero formats back to full range

  10 octobre 2020, par Jan Ekström

  swscale/utils : override forced-zero formats back to full range
  Fixes vf_scale outputting RGB AVFrames with limited range flagged
  
  in case either input or output specifically sets the range.
  This is the reverse of the logic utilized for RGB and PAL8 content
  
  in sws_setColorspaceDetails.
  

  • [DH] libswscale/utils.c