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• How to do Slow Motion video in IOS

  17 janvier 2017, par 2vision2

  I have to do "slow motion" in a video file along with audio, in-between some frames and need to store the ramped video as a new video.

  Ref : http://www.youtube.com/watch?v=BJ3_xMGzauk (watch from 0 to 10s)

  From my analysis, I’ve found that AVFoundation framework can be helpful.

  Ref :
  http://developer.apple.com/library/ios/#documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/00_Introduction.html

  Copy and pasted from the above link :

  "
  Editing
  AV Foundation uses compositions to create new assets from existing pieces of media (typically, one or more video and audio tracks). You use a mutable composition to add and remove tracks, and adjust their temporal orderings. You can also set the relative volumes and ramping of audio tracks ; and set the opacity, and opacity ramps, of video tracks. A composition is an assemblage of pieces of media held in memory. When you export a composition using an export session, it’s collapsed to a file.
  On iOS 4.1 and later, you can also create an asset from media such as sample buffers or still images using an asset writer.

  "

  Questions :
  Can I do " slow motion " the video/audio file using the AVFoundation framework ? Or Is there any other package available ? If i want to handle audio and video separately, please guide me how to do ?

  Update : : Code For AV Export Session :

   NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  
      NSString *outputURL = paths[0];
  
      NSFileManager *manager = [NSFileManager defaultManager];
  
      [manager createDirectoryAtPath:outputURL withIntermediateDirectories:YES attributes:nil error:nil];
  
      outputURL = [outputURL stringByAppendingPathComponent:@"output.mp4"];
  
      // Remove Existing File
  
      [manager removeItemAtPath:outputURL error:nil];
  
      AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:self.inputAsset presetName:AVAssetExportPresetLowQuality];
  
      exportSession.outputURL = [NSURL fileURLWithPath:outputURL]; // output path;
  
      exportSession.outputFileType = AVFileTypeQuickTimeMovie;
  
      [exportSession exportAsynchronouslyWithCompletionHandler:^(void) {
  
          if (exportSession.status == AVAssetExportSessionStatusCompleted) {
  
              [self writeVideoToPhotoLibrary:[NSURL fileURLWithPath:outputURL]];
  
              ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
  
              [library writeVideoAtPathToSavedPhotosAlbum:[NSURL fileURLWithPath:outputURL] completionBlock:^(NSURL *assetURL, NSError *error){
  
                  if (error) {
  
                      NSLog(@"Video could not be saved");
  
                  }
  
              }];
  
          } else {
  
              NSLog(@"error: %@", [exportSession error]);
  
          }
  
      }];

• FFMpeg concat streams

  9 juillet 2017, par chourizo

  I am trying to receive two H264 UDP streams from two cameras, and save them to one file (so they are always synchronized). I tried a lot of things, but it always says that there is no video on the second stream (although I can watch it).

  ffmpeg -probesize 20M -analyzeduration 20M -i udp://@127.0.0.1:1234 -probesize 20M -analyzeduration 20M -i udp://@127.0.0.1:1235 -filter_complex "[0:v]fps=15,scale=320:240,setsar=1/1,setpts=PTS-STARTPTS[v0]; [1:v]fps=15,scale=320:240,setsar=1/1,setpts=PTS-STARTPTS[v1]; [v0][v1]concat=n=2:v=1:a=0 [v0] [v1]" -map "[v0]" -map "[v1]" -threads 0 -y kk.ts

  Is it possible to apply the concat to real time streams, so we have a video with two programs as a result ?

• Ramp- Slow Motion in IOS

  26 juin 2013, par 2vision2

  I have to do "ramp-slow motion" in a video file along with audio, in-between some frames and need to store the ramped video as a new video.

  Ref : http://www.youtube.com/watch?v=BJ3_xMGzauk (watch from 0 to 10s)

  From my analysis, I've found that AVFoundation framework can be helpful.

  Ref :
  http://developer.apple.com/library/ios/#documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/00_Introduction.html

  Copy and pasted from the above link :

  "
  Editing
  AV Foundation uses compositions to create new assets from existing pieces of media (typically, one or more video and audio tracks). You use a mutable composition to add and remove tracks, and adjust their temporal orderings. You can also set the relative volumes and ramping of audio tracks ; and set the opacity, and opacity ramps, of video tracks. A composition is an assemblage of pieces of media held in memory. When you export a composition using an export session, it's collapsed to a file.
  On iOS 4.1 and later, you can also create an asset from media such as sample buffers or still images using an asset writer.

  "

  Questions :
  Can I "ramp-slow mote" the video/audio file using the AVFoundation framework ? Or Is there any other package available ? If i want to handle audio and video separately, please guide me how to do ?