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• Is there a set of working P/Invoke declarations for FFMpeg, libavutil, libavformat and libavcodec in .NET ?

  11 février 2014, par casperOne

  I'm currently looking to access libavutil, libavformat and libavcodec (all part of FFMpeg) from .NET.

  Currently, I'm getting the libraries from the automated builds of the shared FFMpeg package performed every night for Windows 32-bit.

  I am also using the code from the ffmpeg-sharp project. In that project, I have removed a number of classes that were not compiling (they are wrapper classes not the P/Invoke declarations).

  The code compiles fine, but I am running into a few issues.

  First, it appears that the build of av*.dll uses the cdecl calling convention, as I was receiving a number of PInvokeStackImbalanceException when trying to call av_open_input_file. This was easy enough to change to get it to work right. The AVFormatContext structure is populated.

  After that, I want to call av_find_stream_info to get information about the streams in the file. However, when calling that with the AVFormatContext retrieved from the call to av_open_input_file, an AccessViolationException is thrown indicating that I am trying to read or write from protected memory.

  Has anyone used P/Invoke to access the libavutil, libavformat and libavcodec dll libraries through P/Invoke and have gotten it to work ?

  I should mention that working with the command-line version of FFMpeg, while a solution, is not a viable solution in this case, access needs to occur through the libraries. The reason for this is that I'd have to thrash the disk way too much to do what I need to do (I have to do a frame-by-frame analysis of some very high definition video) and I want to avoid the disk as much as possible.

• ffmpeg command not working with Windows XP when files have spaces

  25 février 2014, par user1665130

  I have a wpf application program for video audio merging using a command line tool ffmpeg.
  I can successfully merge files in Windows 7. But when I try to run my program on Windows XP it shows errors.

  Here I include my command line code.

   ffmpeg -i C:\Users\vishnu.aravind\Desktop\SUNP.AVI -i C:\Users\vishnu.aravind\Desktop\Alarm03.wav -c:v copy -c:a aac -strict experimental C:\Users\vishnu.aravind\Desktop\ Vishnu Aravind\new.avi

  I made some research on this and i find out that if the input filenames and output filenames contain extra spaces in them, normally ffmpeg won't take it. Suppose if I edit my above code to

   ffmpeg -i C:\Users\vishnu.aravind\Desktop\SUNP.AVI -i C:\Users\vishnu.aravind\Desktop\Alarm03.wav -c:v copy -c:a aac -strict experimental C:\Users\vishnu.aravind\Desktop\VishnuAravind\new.avi 

  this will successfully execute.

  How to solve if I want the output to be saved to a folder whose folder name contains an extra space ?

• Revision e890c2579b : add a context tree structure to encoder This patch sets up a quad_tree structur

  17 avril 2014, par Jim Bankoski

  Changed Paths :
   Modify /vp9/encoder/vp9_block.h

  
   Add /vp9/encoder/vp9_context_tree.c

  
   Add /vp9/encoder/vp9_context_tree.h

  
   Modify /vp9/encoder/vp9_encodeframe.c

  
   Modify /vp9/encoder/vp9_firstpass.c

  
   Modify /vp9/encoder/vp9_onyx_if.c

  
   Modify /vp9/vp9cx.mk

  
  
  add a context tree structure to encoder

  This patch sets up a quad_tree structure (pc_tree) for holding all of
  pick_mode_context data we use at any square block size during encoding
  or picking modes. That includes contexts for 2 horizontal and 2 vertical
  splits, one none, and pointers to 4 sub pc_tree nodes corresponding
  to split. It also includes a pointer to the current chosen partitioning.

  This replaces code that held an index for every level in the pick
  modes array including : sb_index, mb_index,
  b_index, ab_index.

  These were used as stateful indexes that pointed to the current pick mode
  contexts you had at each level stored in the following arrays

  array ab4x4_context[][][],
  sb8x4_context[][][], sb4x8_context[][][], sb8x8_context[][][],
  sb8x16_context[][][], sb16x8_context[][][], mb_context[][], sb32x16[][],
  sb16x32[], sb32_context[], sb32x64_context[], sb64x32_context[],
  sb64_context

  and the partitioning that had been stored in the following :
  b_partitioning, mb_partitioning, sb_partitioning, and sb64_partitioning.

  Prior to this patch before doing an encode you had to set the appropriate
  index for your block size ( switch statement), update it ( up to 3
  lookups for the index array value) and then make your call into a recursive
  function at which point you'd have to call get_context which then
  had to do a switch statement based on the blocksize, and then up to 3
  lookups based upon the block size to find the context to use.

  With the new code the context for the block size is passed around directly
  avoiding the extraneous switch statements and multi dimensional array
  look ups that were listed above. At any level in the search all of the
  contexts are local to the pc_tree you are working on (in ?).

  In addition in most places code that used to call sub functions and
  then check if the block size was 4x4 and index was > 0 and return
  now don't preferring instead to call the right none function on the inside.

  Change-Id : I06e39318269d9af2ce37961b3f95e181b57f5ed9