5

我需要在内存中保存一些来自 captureSession 的视频帧，并在发生“某些事情”时将它们写入文件。

与此解决方案类似，我使用此代码将框架放入 NSMutableArray：

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection
{       
    //...
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    uint8 *baseAddress = (uint8*)CVPixelBufferGetBaseAddress(imageBuffer);
    NSData *rawFrame = [[NSData alloc] initWithBytes:(void*)baseAddress length:(height * bytesPerRow)];
    [m_frameDataArray addObject:rawFrame];
    [rawFrame release];
    //...
}

这要写入视频文件：

-(void)writeFramesToFile
{
    //...
    NSDictionary *outputSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                    [NSNumber numberWithInt:640], AVVideoWidthKey,
                                    [NSNumber numberWithInt:480], AVVideoHeightKey,
                                    AVVideoCodecH264, AVVideoCodecKey,
                                    nil ];
    AVAssetWriterInput *bufferAssetWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:outputSettings];
    AVAssetWriter *bufferAssetWriter = [[AVAssetWriter alloc]initWithURL:pathURL fileType:AVFileTypeQuickTimeMovie error:&error];
    [bufferAssetWriter addInput:bufferAssetWriterInput];

    [bufferAssetWriter startWriting];
    [bufferAssetWriter startSessionAtSourceTime:startTime];
    for (NSInteger i = 1; i < m_frameDataArray.count; i++){
        NSData *rawFrame = [m_frameDataArray objectAtIndex:i];
        CVImageBufferRef imgBuf = [rawFrame bytes];
        [pixelBufferAdaptor appendPixelBuffer:imgBuf withPresentationTime:CMTimeMake(1,10)]; //<-- EXC_BAD_ACCESS
        [rawFrame release];
    }
    //... (finishing video file)
}

但是 imgBuf 参考有问题。有什么建议么？提前致谢。

4

2 回答 2

4

您应该在访问 imageBuffer 的属性之前锁定基地址。

CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(imageBuffer, 0);
uint8 *baseAddress = (uint8*)CVPixelBufferGetBaseAddress(imageBuffer);
NSData *rawFrame = [[NSData alloc] initWithBytes:(void*)baseAddress length:(height * bytesPerRow)];
[m_frameDataArray addObject:rawFrame];
CVPixelBufferUnlockBaseAddress(imageBuffer, 0);
于 2011-06-04T11:53:17.903 回答
2

这已经很老了，但是为了帮助那些后来的人，有一些问题需要解决：

  1. 按照亚历克斯的回答建议复制时锁定/解锁基地址
  2. CVImageBufferRef 是一个抽象基类类型。您想使用 CVPixelBufferCreateWithBytes 来创建一个实例，而不仅仅是对原始像素字节进行类型转换。（系统需要知道这些像素的大小/格式）
  3. 您应该直接从原始数据创建和存储新的 CVPixelBuffer，而不是使用中间 NSData 进行存储。这样你只需要做一份而不是两份。
于 2015-02-13T18:55:21.670 回答