Deep copy of CMSampleBufferRef - ios

Question

I'm trying to perform a deep copy of a CMSampleBufferRef for audio and video connection ? I need to use this buffer for delayed processing. Can somebody helper here by point to a sample code.
Thanks

Answer 1

I solve this problem
I needs access to the sample data for a long period of time.
try many way:
CVPixelBufferRetain -----> program broken
CVPixelBufferPool -----> program broken
CVPixelBufferCreateWithBytes ----> it can solve this program,but this will reduce performance,Apple is not recommended to do so
CMSampleBufferCreateCopy --->it is ok, and apple recommended it.
List : To maintain optimal performance, some sample buffers directly reference pools of memory that may need to be reused by the device system and other capture inputs. This is frequently the case for uncompressed device native capture where memory blocks are copied as little as possible. If multiple sample buffers reference such pools of memory for too long, inputs will no longer be able to copy new samples into memory and those samples will be dropped. If your application is causing samples to be dropped by retaining the provided CMSampleBuffer objects for too long, but it needs access to the sample data for a long period of time, consider copying the data into a new buffer and then calling CFRelease on the sample buffer (if it was previously retained) so that the memory it references can be reused.
REF:https://developer.apple.com/reference/avfoundation/avcapturefileoutputdelegate/1390096-captureoutput
that might be what you need:
pragma mark -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 to use for a long period of time
- (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;
}
}
}
then you can use it such this:
-(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

I do this. CMSampleBufferCreateCopy can indeed deep copy
but a new problem is appear
captureOutput delegate doesn't work