AVFoundation to reproduce a video loop

Question

I need to reproduce a video indefinitely (restarting the video when it ends) in my OpenGL application. To do so I'm trying to utilize AV foundation. I created an AVAssetReader and an AVAssetReaderTrackOutput and I utilize the copyNextSampleBuffer method to get CMSampleBufferRef and create an OpenGL texture for each frame.

    NSString *path = [[NSBundle mainBundle] pathForResource:videoFileName ofType:type];
    _url = [NSURL fileURLWithPath:path];

    //Create the AVAsset 
    _asset = [AVURLAsset assetWithURL:_url];

    //Get the asset AVAssetTrack
    NSArray *arrayAssetTrack = [_asset tracksWithMediaType:AVMediaTypeVideo];
    _assetTrackVideo = [arrayAssetTrack objectAtIndex:0];

    //create the AVAssetReaderTrackOutput
    NSDictionary *dictCompressionProperty = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id) kCVPixelBufferPixelFormatTypeKey];
    _trackOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:_assetTrackVideo outputSettings:dictCompressionProperty];

    //Create the AVAssetReader
    NSError *error;
    _assetReader = [[AVAssetReader alloc] initWithAsset:_asset error:&error];
    if(error){
        NSLog(@"error in AssetReader %@", error);
    }
    [_assetReader addOutput:_trackOutput];
    //_assetReader.timeRange = CMTimeRangeMake(kCMTimeZero, _asset.duration);

    //Asset reading start reading
    [_assetReader startReading];

And in -update method of my GLKViewController I call the following:

if (_assetReader.status == AVAssetReaderStatusReading){
    if (_trackOutput) {
        CMSampleBufferRef sampleBuffer = [_trackOutput copyNextSampleBuffer];
        [self createNewTextureVideoFromOutputSampleBuffer:sampleBuffer]; //create the new texture
    }
}else if (_assetReader.status == AVAssetReaderStatusCompleted) {
    NSLog(@"restart");
    [_assetReader startReading];
}

All work fine until the AVAssetReader is in the reading status but when it finished reading and I tried to restart the AVAssetReading with a new call [_assetReader startReading], the application crash without output. What I'm doing wrong? It is correct to restart an AVAssetReading when it complete his reading?

Answer 1

AVAssetReader doesn't support seeking or restarting, it is essentially a sequential decoder. You have to create a new AVAssetReader object to read the same samples again.

Answer 2

Thanks Costique! Your suggestion brings me back on the problem. I finally restarted the reading by creating a new AVAssetReader. However in order to do that I noted that a new AVAssetReaderTrackOutput must be created and added to the new AVAssetReader e.g.

[newAssetReader addOutput:newTrackOutput];