AVFoundation重现视频循环

问题描述

我需要在OpenGL应用程序中无限期地复制视频(在结束时重新启动视频).为此，我正在尝试利用AV基础.我创建了一个AVAssetReader和AVAssetReaderTrackOutput，并使用copyNextSampleBuffer方法获取CMSampleBufferRef并为每个帧创建一个OpenGL纹理.

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];

在我的GLKViewController的-update方法中，我调用以下内容:

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];
}

一切正常，直到AVAssetReader处于读取状态，但是当它完成读取并且我尝试通过新的调用[_assetReader startReading]重新启动AVAssetReading时，应用程序崩溃，无输出.我做错了什么?完成阅读后重新启动AVAssetReading是正确的吗?

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?

推荐答案

AVAssetReader不支持查找或重新启动，它本质上是一个顺序解码器.您必须创建一个新的AVAssetReader对象才能再次读取相同的样本.

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.

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