我正在尝试在 iOS 上播放视频 (MP4/H.263)，但得到的结果非常模糊。这是初始化资产读取的代码：
mTextureHandle = [self createTexture:CGSizeMake(400,400)];
NSURL * url = [NSURL fileURLWithPath:file];
mAsset = [[AVURLAsset alloc] initWithURL:url options:NULL];
NSArray * tracks = [mAsset tracksWithMediaType:AVMediaTypeVideo];
mTrack = [tracks objectAtIndex:0];
NSLog(@"Tracks: %i", [tracks count]);
NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey;
NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA];
NSDictionary * settings = [[NSDictionary alloc] initWithObjectsAndKeys:value, key, nil];
mOutput = [[AVAssetReaderTrackOutput alloc]
initWithTrack:mTrack outputSettings:settings];
mReader = [[AVAssetReader alloc] initWithAsset:mAsset error:nil];
[mReader addOutput:mOutput];
对于读者 init 来说这么多，现在是实际的纹理：
CMSampleBufferRef sampleBuffer = [mOutput copyNextSampleBuffer];
CVImageBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress( pixelBuffer, 0 );
glBindTexture(GL_TEXTURE_2D, mTextureHandle);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 600, 400, 0, GL_BGRA_EXT, GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddress( pixelBuffer ));
CVPixelBufferUnlockBaseAddress( pixelBuffer, 0 );
CFRelease(sampleBuffer);
一切正常......除了渲染图像看起来像这样; 切片和歪斜？
我什至尝试查看AVAssetTrack的首选转换矩阵，但无济于事，因为它总是返回CGAffineTransformIdentity.
旁注：如果我将源切换到相机，图像会渲染得很好。我错过了一些减压步骤吗？这不应该由资产阅读器处理吗？
谢谢！