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• Crash in ffmpeg avcodec_free_context in one application but not in other

  5 novembre 2017, par geekowl

  I am building an application in C++ on Windows 10 using Microsoft Visual Studio 2012 Professional.

  I have created a wrapper library around ffmpeg (libavcodec) to encode video in H.264 format using libx264. This wrapper contains following functions :

  Initialize()
  
  Open()
  
  EncodeFrame()
  
  Close()
  
  Uninitialize()

  I created a test application to test the wrapper library. The test application works perfectly fine.

  When I use the wrapper library in my actual main application, the main application crashes in Close() API. Inside close, it crashes in avcodec_free_context(). The difference between the main application and the test application is that the main application links with some more dependent libraries that test application does not link with.

  To debug the problem in the main application, I put avcodec_free_context() in Open() after the context is allocated. The crash occurs if avcodec_free_context() is put at a certain point as shown below.

  pCodecContext = avcodec_alloc_context3(pCodec);
  
  
  
  // <---- No crash here.
  
  
  
  pCodecContext->bit_rate = 200000;
  
  pCodecContext->width = 320;
  
  pCodecContext->height = 240;
  
  .
  
  .
  
  .
  
  if (pCodec->id == AV_CODEC_ID_H264)
  
  {
  
      av_opt_set(pCodecContext->priv_data, "preset", "slow", 0);
  
      av_opt_set(pCodecContext->priv_data, "tune", "zerolatency", 0);
  
  }
  
  
  
  pCodecContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
  
  
  // <-- No crash here
  
  
  
  if (avcodec_open2(pCodecContext, pCodec, NULL) < 0)
  
  {
  
      return -1;
  
  }
  
  
  
  // <-- Crash here [avcodec_free_context(&pCodecContext);]

  What is a correct approach to identify and resolve this problem ?

  Thanks in advance.

  Update

  I found out that ffmpeg was built using gcc. That was causing the crash. I rebuilt ffmpeg using Visual Studio. That solved problem.

• Museum of Multimedia Software, Part 1

  14 août 2010, par Multimedia Mike — Software Museum

  Many years ago, I found a boneyard of old software, much of it related to the creation and processing of multimedia. I was permitted to liberate anything of my choosing from this cache. This is the same pile where I found this Apple QuickTime format spec as well as this perfect form factor floppy disc box. So I have been sitting on the stuff for awhile.

  I thought I might get the chance to study it a bit more closely one day. But now I’m interested in getting rid of it. Before I do, it’s more or less traditional for me to photograph it and post it on one blog or another. Also, if you know of any software collection groups who would be interested in taking this stuff off my hands, do let me know.

  As usual, click a picture for a much larger image.

  Paracomp FilmMaker
  This is easily the most distinctive piece in this collection and it’s easy to see why— the software is packaged in a film cannister. Still sealed, and I don’t have a good reason to open it now.

  
  
  

  "The Professional Animation/Presentation Program for the Macintosh." No copyright date on the packaging, though the front does mention a 1990 award. System requirements : Mac OS 6.0.5, 5 MB RAM, 32-bit QuickDraw, math coprocessor.

  Strata VideoShop
  Version 4.5 (and not for resale), still shrink-wrapped. "The Digital Video Editor for Creative Professionals."

  
  
  

  System requirements : PowerMac with 5 MB RAM (8 MB recommended), Mac OS 7.5.

  BeatWare e-Picture
  "The Professional’s Choice for Designing Animated Web Graphics." Claims a best of show award for 1999 MacWorld New York Expo.

  
  
  

  System requirements : PowerMac with Mac OS 8, 32MB RAM, 10 MB of HD space and a 256-color adapter.

  BeatWare eZ-Motion
  Another offering from BeatWare. "The fastest and easiest way to create animations and graphics for the Web."

  
  
  

  This one is for either Mac or Windows. 32 MB RAM and 25 MB HD space required. Works with Mac OS 8.5, 8.6, or 9.0, or Windows 98, NT, or 2000.

  Much more to come...

• How to process video stream ?

  27 avril 2016, par sharpener

  I would like to ask some experienced multimedia professional how to proceed with following task :

  Given URL provides video stream and we would like to get access to decoded frames (byte stream in memory) in managed Win7+ application (C#). We don’t want to render/present the frames the standard way. The video format is known but not fixed (might get changed between two successive sessions, but we will know the parameters).

  So far, I have found there are several methods and I have build following picture in my mind :

  1. ffmpeg wrapper
     • Pros
       1. Self contained (no dependency to windows technologies)
       2. Powerful
     • Cons
       1. Little more complex to understand
       2. Lot of different wrapping variants (FFmpeg.NET, ffmpeg-sharp, ffmpeg-shard, FFmpeg.AutoGen, ...)
  2. DirectShow wrapper
     • Pros
       1. Widely used/supported technology (variaous filters freely available)
       2. Nice/detailed documentation on MSDN
     • Cons
       1. Quite old
       2. Considered obsolete from the point of author’s view (available only for desktop model on runtime >= Win8)
  3. MediaFoundation wrapper
     • Pros
       1. Theoretical successor of DirectShow, so should be available in the future
     • Cons
       1. Seems to be not as good as DirectShow
       2. Not very popular, limited "community" support
  4. FFmpegInterop wrapper
     • Pros
       1. Microsoft’s open source wrapper alternative
     • Cons
       1. Not available for runtime < Win8