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• Recording application output to video using FFmpeg (or similar)

  15 décembre 2011, par John

  We have a requirement to lets users record a video of our 3D application. I can already grab the individual rendered frames so this question is specifically about how to write frames into a video file.

  I don't think writing each frame as a separate file and post-processing is a workable option.

  I can look at options to record to a simple video file for later optimising/encoding, or writing directly to a sensibly encoded format.

  FFmpeg was suggested in another post but it looks a bit daunting to me. Is it the best option, if not what can be suggested ? We can work with LGPL but not full GPL.

  We're working on Windows (Win32 not MFC) in C++. Sample/pseudo code with your recommended library is very much appreciated... basically after how to do 3 functions :

  • startRecording() does whatever initialization is needed
  • recordFrame() takes pointer to frame data and encodes it, ideally with timing data
  • endRecording() finalizes the video file, shuts down video system, etc

• FFMPEG for iPhone recorded video encoding

  16 décembre 2011, par Sarah

  Hi found lots and lots of links for video encoding through ffmpeg 1,2,3,4 etc but they all start with using terminal commands but when i try to implement any on terminal like :

  git clone git ://github.com/lajos/iFrameExtractor.gitit says that-bash : git : command not found.

  Also as per my knowledge it is not possible to use terminal command on iPhone. Can anybody point out how to encode a video recorded through ffmpeg in mp4 format and also to reduce the size of the video ?Thanks in advance.

  EDIT :
  I am already implementing this method to resize my video and it successfully takes place and I am able to send the video on server but then on server side it's giving problem in retrieving the data and to use it.

  - (void)imagePickerController:(UIImagePickerController *)picker 
  
  didFinishPickingMediaWithInfo:(NSDictionary *)info
  
  {
  
      [self convertVideoToLowQuailtyWithInputURL:videoURL1 outputURL:[NSURL fileURLWithPath:videoStoragePath] handler:^(AVAssetExportSession *exportSession)
  
       {
  
           if (exportSession.status == AVAssetExportSessionStatusCompleted)
  
           {
  
               NSLog(@"%@",exportSession.error);
  
               printf("completed\n");
  
           }
  
           else
  
           {
  
               NSLog(@"%@",exportSession.error);
  
               printf("error\n");
  
           }
  
       }];
  
  }
  
  
  
  - (void)convertVideoToLowQuailtyWithInputURL:(NSURL*)inputURL 
  
                                     outputURL:(NSURL*)outputURL 
  
                                       handler:(void (^)(AVAssetExportSession*))handler
  
  {
  
      [[NSFileManager defaultManager] removeItemAtURL:outputURL error:nil];
  
      AVURLAsset *asset = [AVURLAsset URLAssetWithURL:inputURL options:nil];
  
      AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetLowQuality];
  
      exportSession.outputURL = outputURL;
  
      exportSession.outputFileType = AVFileTypeQuickTimeMovie;
  
      [exportSession exportAsynchronouslyWithCompletionHandler:^(void) 
  
       {
  
           handler(exportSession);
  
           [exportSession release];
  
       }];
  
  }

• Selecting a library / framework for video capture & recording

  21 décembre 2011, par Saurabh Gandhi

  In one of the project that we have undertaken we are looking for a video capture & recording library. Our groundwork (based on google search) shows that vlc (libvlc), ffmpeg (libavcodec) and gstreamer are the three popular free and open source libraries / multimedia frameworks available for the same. How do these libraries compare on the following parameters :

  1. Licensing policy to allow use within a commercial product without the need to open source any of the components of the product that is using the library
  2. Ability to be used effectively in a multi-threaded environment (library should be inherently thread-safe)
  3. Easy to use and maintain
  4. Documentation : API should be well documented...this is relative... :)

  Our primary intention is to be able to capture RTSP video streams (H.264/MPEG-2/MJPEG encoded), convert these streams to raw video / frames so that it can be used for analysis / processing and later on compress these frames and store it on the disk in the form of an MP4 file (using MPEG2 / H.264 encoding).

  P.S. We understand that FFmpeg is also one of the components of vlc since vlc uses libavcodec library. Is the same true for gstreamer as well ? Does it have any ffmpeg dependency ?

  Awaiting your responses.

  Regards,

  Saurabh Gandhi