使用AVAssetReaderVideoCompositionOutput导出中途，然后使用AVFoundationErrorDomain Code = -11800退出

Question

我已经从AVAssets构建了AVMutableComposition和VideoComposition，并且能够播放它。 我也可以使用AVAssetExportSession导出它，但是AVAssetExportSession不能提供很多设置控制，所以我使用AVAssetReader / AVAssetWriter导出它，但不幸的是我收到了一个我不理解的错误，只是部分写了输出文件。

这是我到目前为止的代码。 我已经遗漏了作者和尽可能多的其他东西（包括一些错误检查），我认为这与使代码更容易阅读无关，因为它很多。 请注意，我还没有处理音频轨道 - 我试图一步一步，但也许这是我的问题？

可变asset是AVMutableComposition。

// ------- reader
_assetReader = [AVAssetReader assetReaderWithAsset:asset error:error];

_assetReader.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration);
_duration = asset.duration;

// --- video reader
NSArray *videoTracks = [asset tracksWithMediaType:AVMediaTypeVideo];

NSDictionary *videoOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];

_assetReaderOutput = [AVAssetReaderVideoCompositionOutput assetReaderVideoCompositionOutputWithVideoTracks:videoTracks
                                                                                             videoSettings:videoOptions];
((AVAssetReaderVideoCompositionOutput *)_assetReaderOutput).videoComposition = composition;
[_assetReader addOutput:_assetReaderOutput];


// -- leaving out the export settings and construction
//    of the assetWriter since that doesn't seem to be the issue


// -- here's the actual export:

[self.assetWriter startWriting];
[self.assetWriter startSessionAtSourceTime:kCMTimeZero];
[self.assetReader startReading];


CMSampleBufferRef buffer;


while ( [self.assetReader status]==AVAssetReaderStatusReading )
{
    if(![self.assetWriterInput isReadyForMoreMediaData])
        continue;

    buffer = [self.assetReaderOutput copyNextSampleBuffer];


    NSLog(@"READING");

    if(buffer)
        [self.assetWriterInput appendSampleBuffer:buffer];

    NSLog(@"WRITTING...");


}
if( self.assetReader.status == AVAssetReaderStatusFailed ) {
    NSLog( @"%@", self.assetReader.error ); //<--------- I get a problem here
}


//Finish the session:
[self.assetWriterInput markAsFinished];
[self.assetWriter finishWriting];
NSLog(@"Write Ended");

问题是循环退出很短的时间后我得到这个输出：

Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo=0x17f1dfa0 {NSLocalizedDescription=The operation could not be completed, NSUnderlyingError=0x191617f0 "The operation couldn’t be completed. (OSStatus error -308.)", NSLocalizedFailureReason=An unknown error occurred (-308)}

Answer 1

我似乎遵循了一些不好的示例代码，而不是正确的示例代码，这非常清楚，如果非常冗长，关于如何执行此操作：

https://developer.apple.com/library/Mac/DOCUMENTATION/AudioVideo/Conceptual/AVFoundationPG/Articles/05_Export.html#//apple_ref/doc/uid/TP40010188-CH9-SW2

虽然我已经完全重写了我的代码，但我认为我遇到的具体问题不是在[self.assetReaderOutput copyNextSampleBuffer]返回的CMSampleBufferRef上调用CFRelease。 你需要在循环中做到这一点。