Recherche avancée

Sur d’autres sites (18400)

• Extracting frame referencing information in h264

  23 août 2016, par Sangwook Bae

  I’m trying to extract the frame (slice) information from the mp4 file that contains the h264 encoded media. Especially, I need the slice size, slice type, DTS, reference frame list.

  Through the stss box and stsz box, I can extract the information about the size, type.

  However, I cannot find any information about how to extract the reference frame list for the certain . Which field or box should I look into for extracting frame referencing information ? (For example, in case of B frame, the B frame refers the other frames frame 3 and 4)

  The main reason of extracting these information is that I am trying to construct the frame dependency map. (e,g Frame A which is 15235 bytes size needs Frame B, C for decoding, Frame B’s size is 4222 bytes and need frame D ...etc)

  Thanks.

• Merge commit ’e30b068ef79f604ff439418da07f7e2efd01d4ea’

  29 juin 2013, par Michael Niedermayer

  Merge commit ’e30b068ef79f604ff439418da07f7e2efd01d4ea’
  * commit ’e30b068ef79f604ff439418da07f7e2efd01d4ea’ :
  
    wmapro : make sure there is room to store the current packet
  The check is replaced by an assert as it is impossible to occur
  
  See : 780d45473c32fa356c8ce385c3ea4692567c3228
  Merged-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/wmaprodec.c

• How to do Slow Motion video in IOS

  4 mai 2022, 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]);
        }
    }];