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• Revision fd44975bc8 : Make Rand8Extremes more extreme Previous code didn't do what was expected, we w

  19 avril 2013, par John Koleszar

  Changed Paths :
   Modify /test/acm_random.h

  
  
  Make Rand8Extremes more extreme

  Previous code didn't do what was expected, we want numbers within 16 of
  the extrema.

  Change-Id : I20c18627c482ec66e8405ddad74ca9276c0c65dc

• avformat_write_header produces invalid header (resulting MPG broken)

  24 janvier 2013, par TheSHEEEP

  I am rendering a video file from input pictures that come from a 3D engine at runtime (I don't pass an actual picture file, just RGB memory).
  This works perfectly when outputting MP4 using CODEC_ID_H264 as video codec.

  But when I want to create an MPG file using CODEC_ID_MPEG2VIDEO, the resulting file is simply broken. No player can play the video correctly and when I then want to concatenate that MPG with another MPG file, and transform the result MP4 in another step, the resulting .mp4 file has both videos, but many frames from the original MPG video (and only video ! Sound works fine) are simply skipped.

  At first I thought the MPG -> MP4 conversion was the problem, but then I noticed that the initial MPG, which comes from the video render engine, is already broken, which would speak for broken headers. Not sure if it is the system or sequence headers that are broken, though.
  Or if it could be something totally different.

  If you want to have a look, here is the file :
  http://www.file-upload.net/download-7093306/broken.mpg.html

  Again, the exact same muxing code works perfectly fine when directly creating an MP4 from the video render engine, so I'm pretty sure the input data, swscale(), etc. is correct. The only difference is that CODEC_ID_H264 is used and some additional variables (like qmin, qmax, etc.) are set, which are all specific to H264 so should not have an impact.

  Also, neither avformat_write_header nor av_write_trailer report an error.

  As an additional info, when viewing the codec data of the MPG in VLC player, it is not able to show the FPS, resolution and format (should show 640x360, 30 fps and 4:2:0 YUV).

  I am using a rather new (2-3 months old, maybe) FFmpeg version, which I compiled from sources with MinGW.

  Any ideas on how to resolve this would be welcome. Currently, I am out of those :)

• ffmpeg video streaming deep understanding

  14 novembre 2012, par Stefan Alexandru

  The main question is if it is possible to somehow go around the frame index checking that ffmpeg does when writing the frame to a file.

  Now I will explain my exact problem so you can understand better what I need or maybe think of an alternative solution.

  Problem n0.1 : I am getting video stream from two independent cameras and for some reason I want to save it in the same video file. First the frames from the first camera and then the frames from the second. When writing the frames from the second camera av_write_frame would return the error code -22 and will fail to add the frame. That's because the writing context is expecting a frame index following the index of the previously written frame (the last frame from camera 1) but he receives a frame with the index 0, the first frame from the second camera.

  Problem no.2 : Consider the following problem independently to the first one.
  I am trying to save a video stream to a file but the frame rate is double the real speed. So because I couldn't find any working solution to speed down the frame rate i thought to write every frame twice in the video file. But it won't make any difference to the frame rate.
  I also tried a different approach on the frame rate problem but it also failed(question here).

  Any kind of working solution would be highly appreciated.

  Also it's important that I can't use console commands, I need C code, as I need to integrate those functionalities in an Android application that is automated.