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

  30 août 2011, 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.

• Who Invented FLIC ?

  26 mai 2011, par Multimedia Mike — Multimedia History

  I have been reading through “All Your Base Are Belong To Us : How 50 Years of Video Games Conquered Pop Culture” by Harold Goldberg. Despite the title, Zero Wing has yet to be mentioned (I’m about halfway done).

  
  
  

  I just made it through the chapter describing early breakthrough CD-ROM games, including Myst, The 7th Guest, and The 11th Hour. Some interesting tidbits :

  The 7th Guest
  Of course, Graeme Devine created a new FMV format (called VDX, documented here) for The 7th Guest. The player was apparently called PLAY and the book claims that Autodesk was so impressed by the technology that it licensed the player for use in its own products. When I think of an Autodesk multimedia format, I think of FLIC. The VDX coding format doesn’t look too much like FLIC, per my reading.

  Here’s the relevant passage (pp 118-119) :

  Devine began working on creating software within the CD-ROM disk that would play full-motion video. Within days he had a robust but small ninety-kilobyte player called PLAY that was so good, it was licensed by Autodesk, the makers of the best 3-D animation program at the time. Then Devine figured out a way to compress the huge video files so that they would easily fit on two CD-ROMs.

  Googling for “autodesk trilobyte play program” (Trilobyte was the company behind 7th Guest) led me to this readme file for a program called PLAY73 (hosted at Jason Scott’s massive CD-ROM archive, and it’s on a disc that, incidentally, I donated to the archive ; so, let’s here it for Jason’s tireless archival efforts ! And for Google’s remarkable indexing prowess). The file — dated September 10, 1991 — mentions that it’s a FLICK player, copyright Trilobyte software.

  
  
  

  However, it also mentions being a Groovie Player. Based on ScummVM’s reimplementation of the VDX format, Groovie might refer to the engine behind The 7th Guest.

  So now I’m really interested : Did Graeme Devine create the FLIC file format ? Multimedia nerds want to know !

  I guess not. Thanks to Jim Leonard for digging up this item : “I developed the flic file format for the Autodesk Animator.” Jim Kent, Dr. Dobbs Magazine, March 1993.

  The PLAY73 changelog reveals something from the bad old days of DOS/PC programming : The necessity of writing graphics drivers for 1/2 dozen different video adapters. The PLAY73 readme file also has some vintage contact address for Graeme Devine ; remember when addresses looked like these ?

  If you have any comments, please send them to :
  	Compuserve : 72330,3276
  	Genie : G.DEVINE
  	Internet : 72330,3276@compuserve.com
  

  The 11th Hour
  The book didn’t really add anything I didn’t already know regarding the compression format (RoQ) used in 11th Hour. I already knew how hard Devine worked at it. This book took pains to emphasize the emotional toll taken on the format’s creator.

  I wonder if he would be comforted to know that, more than 15 years later, people are still finding ways to use the format.

• compress keynote compatible movie with alpha channel

  26 janvier 2015, par John Smith

  I am creating a movie with alpha channel by converting png-images with imagemagicks convert and then compiling the movie with ffmpeg :

  ffmpeg -i image%04d_t.png -vcodec png -q:v 1 -compression_level 100 transparent.mov

  I can import those movies into the latest (6.5.2) Apple Keynote, but they tend to be very large (560 frames of size 615x189, no sound, 22 sec. = 113 MB). Is there a way to convert the movie to a different format (that is also Keynote compatible) that uses less disk space ?

  A second option would be to use a lower framerate for the same length (=using less frames) - would that save on file size and if so, what command would I use for that ?