读取视频示例的基本AVAssetReader问题

Question

我想通过AVAssetReader阅读视频样本，我遇到了各种各样的路障。某个邮政编码可以从应用程序包中的一个名为“AVAsset”的视频中设置一个Movie.m4v，并使用AVAssetReader遍历视频帧(CMSampleBufferRef)。

下面是我现在使用的一些不起作用的代码

NSString *path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"Movie.m4v"];
AVAsset *avAsset = [[AVURLAsset alloc] initWithURL:[NSURL URLWithString:path] options:nil];
NSError *error = nil;
AVAssetReader *reader = [[AVAssetReader alloc] initWithAsset:avAsset error:&error]; // crashing right around here!

// I've gotten avassetreader to not crash upon initialization by grabbing an asset from the ALAssetsLibrary but it says it has 0 tracks!

NSArray *videoTracks = [avAsset tracksWithMediaType:AVMediaTypeVideo]; 
AVAssetTrack *videoTrack = [videoTracks objectAtIndex:0];
NSDictionary *options = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
AVAssetReaderTrackOutput *asset_reader_output = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoTrack outputSettings:options];
[reader addOutput:asset_reader_output];
[reader startReading];

CMSampleBufferRef buffer;
while ( [reader status]==AVAssetReaderStatusReading ){

    buffer = [asset_reader_output copyNextSampleBuffer];
    NSLog(@"READING");



}

Answer 1

很可能是因为[NSURL URLWithString:path]而崩溃。您应该使用[NSURL fileURLWithPath:path]代替。

Answer 2

在使用磁道之前，您需要要求您的AVAsset异步加载其轨道属性。