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.
AVFoundation to reproduce a video loop
-
30-03-2022 - |
Pergunta
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?
Solução
Outras dicas
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];