CMSampleBufferRef的深层拷贝

Question

我正在尝试执行用于音频和视频连接的CMSampleBufferRef的深层拷贝？我需要使用这个缓冲区来延迟处理。有没有人可以在这里通过指向示例代码来帮助。

谢谢

Answer 1

我解决了这个问题

我需要访问很长一段时间的样本数据。

尝试多种方式：

CVPixelBufferRetain ->程序坏了CVPixelBufferPool ->程序坏了CVPixelBufferCreateWithBytes ->可以解决这个程序，但是这样会降低性能，不建议苹果这样做

CMSampleBufferCreateCopy ->没问题，苹果推荐的。

列表:为了保持最佳性能，一些样本缓冲区直接引用内存池，这些内存池可能需要由设备系统和其他捕获输入重用。这通常是未压缩设备本机捕获的情况，其中复制的内存块尽可能少。如果多个样本缓冲区引用此类内存池的时间过长，则输入将无法再将新样本复制到内存中，并且这些样本将被丢弃。

参考：https://developer.apple.com/reference/avfoundation/avcapturefileoutputdelegate/1390096-captureoutput

这可能就是你所需要的：

pragma -captureOutput

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection{
    if (connection == m_videoConnection) {        
        /* if you did not read m_sampleBuffer ,here you must CFRelease m_sampleBuffer, it is causing samples to be dropped 
        */
        if (m_sampleBuffer) {
            CFRelease(m_sampleBuffer);
            m_sampleBuffer = nil;
        }

        OSStatus status = CMSampleBufferCreateCopy(kCFAllocatorDefault, sampleBuffer, &m_sampleBuffer);
        if (noErr != status) {
            m_sampleBuffer = nil;
        }
        NSLog(@"m_sampleBuffer = %p sampleBuffer= %p",m_sampleBuffer,sampleBuffer);
    }
}

pragma mark -get CVPixelBufferRef长时间使用

- (ACResult) readVideoFrame: (CVPixelBufferRef *)pixelBuffer{
    while (1) {
        dispatch_sync(m_readVideoData, ^{
            if (!m_sampleBuffer) {
                _readDataSuccess = NO;
                return;
            }

            CMSampleBufferRef sampleBufferCopy = nil;
            OSStatus status = CMSampleBufferCreateCopy(kCFAllocatorDefault, m_sampleBuffer, &sampleBufferCopy);
            if ( noErr == status)
            {
                 CVPixelBufferRef buffer  = CMSampleBufferGetImageBuffer(sampleBufferCopy);

                 *pixelBuffer = buffer;

                 _readDataSuccess = YES;

                 NSLog(@"m_sampleBuffer = %p ",m_sampleBuffer);

                 CFRelease(m_sampleBuffer);
                 m_sampleBuffer = nil;

             }
             else{
                 _readDataSuccess = NO;
                 CFRelease(m_sampleBuffer);
                 m_sampleBuffer = nil;
             }
        });

        if (_readDataSuccess) {
            _readDataSuccess = NO;
            return ACResultNoErr;
        }
        else{
            usleep(15*1000);
            continue;
        }
    }
}

然后你可以这样使用它：

-(void)getCaptureVideoDataToEncode{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(){
        while (1) {
            CVPixelBufferRef buffer = NULL;
            ACResult result= [videoCapture readVideoFrame:&buffer];
            if (ACResultNoErr == result) {
                ACResult error = [videoEncode encoder:buffer outputPacket:&streamPacket];
                if (buffer) {
                    CVPixelBufferRelease(buffer);
                    buffer = NULL;
                }
                if (ACResultNoErr == error) {
                NSLog(@"encode success");
                }
            }
        }
    });
}  

Answer 2

我这样做。CMSampleBufferCreateCopy确实可以进行深度复制，但出现了一个新问题，即captureOutput委托不起作用