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• cbs : Describe allocate/free methods in tabular form

  27 juillet 2020, par Mark Thompson

  cbs : Describe allocate/free methods in tabular form
  Unit types are split into three categories, depending on how their
  
  content is managed :
  
  * POD structure - these require no special treatment.
  
  * Structure containing references to refcounted buffers - these can use
  
    a common free function when the offsets of all the internal references
  
    are known.
  
  * More complex structures - these still require ad-hoc treatment.
  For each codec we can then maintain a table of descriptors for each set of
  
  equivalent unit types, defining the mechanism needed to allocate/free that
  
  unit content.  This is not required to be used immediately - a new alloc
  
  function supports this, but does not replace the old one which works without
  
  referring to these tables.
  

  • [DH] libavcodec/cbs.c
  • [DH] libavcodec/cbs.h
  • [DH] libavcodec/cbs_internal.h

• avfilter/vf_alphamerge : Fix double-free of AVFilterFormats on error

  7 août 2020, par Andreas Rheinhardt

  avfilter/vf_alphamerge : Fix double-free of AVFilterFormats on error
  The query_formats function of the alphamerge filter tries to allocate
  
  two lists of formats which on success are attached to more permanent
  
  objects (AVFilterLinks) for storage afterwards. If attaching a list
  
  to an AVFilterLink succeeds, the link becomes one of the owners of
  
  the list. Yet if attaching a list to one of its links succeeds and
  
  an error happens lateron, both lists were manually freed, which is wrong
  
  if the list is already owned by one or more links ; these links' pointers
  
  to their lists will become dangling and there will be a double-free/use-
  
  after-free when these links are cleaned up automatically.
  This commit fixes this by removing the custom freeing code ; this will
  
  temporarily add a leaking codepath (if attaching a list not already
  
  owned by a link to a link fails, the list will leak), but this will
  
  be fixed soon by making sure that an AVFilterFormats without owner will
  
  be automatically freed when attaching it to an AVFilterLink fails.
  
  At most one list leaks because as of this commit a new list is only
  
  allocated after the old list has been successfully attached to a link.
  Reviewed-by : Nicolas George <george@nsup.org>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavfilter/vf_alphamerge.c

• how do I fix the permission problem so ffmpeg can write when run from a cgi-script ?

  7 juillet 2022, par NewtownGuy

  I have a shell script in Linux that runs ffmpeg for the purpose of converting video to a series snapshots in response to a command from apache2. The shell script is run from a perl script in /var/www/cgi-bin that is called by apache2. The conversion works fine when I run the shell script from the command line when I login as root. The problem is that ffmpeg cannot write its output when it's run from the cgi-script. With the exception of ffmpeg writing files, the shell script runs from the cgi-script just fine because I enabled it in /etc/sudoers and I run it with sudo. I have read several posts on the use of ffmpeg and setting permissions, and have tried the following without success :

  


  


  1. The full path to the snapshot files being written is given in the ffmpeg command

     


  


  2. I tried placing the shell script that runs ffmpeg into a root folder instead of the same folder, /var/www/cgi-bin, as the perl cgi script

     


  


  3. I gave the folder, /var/www/html/userName/video, where ffmpeg is to write its snapshots, www-data:root ownership instead of the original root:root, and I tried changing its write permission from 755 to 777.

     


  


  4. ffmpeg is installed in the default location, /use/bin

     


  


  


  How do I fix this ?

  


  Thank you in advance.