IOS Receiving video from Network - objective-c

Question

UPDATE
- I have fixed some mistakes in the code below and the images are displayed on the other device, but I have another problem. While video capture is open, the "master" device sends data continuously, sometimes this capture appears on "slave" device and in a very short time, the image "blinks" to blank and repeat this all time for a short period. Any idea about this?
I'm working on a app that's need to send live camera capture and live microphone capture to another device in network.
I have done the connection between devices using a TCP server and publish it with bonjour, this works like a charm.
The most important part is about to send and receive video and audio from "master" device and render it on "slave" device.
First, here a piece of code where the app get the camera sample buffer and transform in UIImage:
#implementation AVCaptureManager (AVCaptureVideoDataOutputSampleBufferDelegate)
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
dispatch_sync(dispatch_get_main_queue(), ^{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
UIImage *image = [self imageFromSampleBuffer:sampleBuffer];
NSData *data = UIImageJPEGRepresentation(image, 0.2);
[self.delegate didReceivedImage:image];
[self.delegate didReceivedFrame:data];
[pool drain];
});
}
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer
{
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(imageBuffer, 0);
size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
size_t bytesPerRow = width * 4;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);
CGContextRef context = CGBitmapContextCreate(
baseAddress,
width,
height,
8,
bytesPerRow,
colorSpace,
kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Little
);
CGImageRef quartzImage = CGBitmapContextCreateImage(context);
UIImage *image = [UIImage imageWithCGImage:quartzImage];
CGImageRelease(quartzImage);
CGColorSpaceRelease(colorSpace);
CGContextRelease(context);
CVPixelBufferUnlockBaseAddress(imageBuffer, 0);
return image;
}
#end
The message "[self.delegate didReceivedImage:image];" is just to test the image capture on master device, and this image works on capture device.
The next is about how to I send it to network:
- (void) sendData:(NSData *)data
{
if(_outputStream && [_outputStream hasSpaceAvailable])
{
NSInteger bytesWritten = [_outputStream write:[data bytes] maxLength:[data length]];
if(bytesWritten < 0)
NSLog(#"[ APP ] Failed to write message");
}
}
Look I'm using RunLoop to write and read streams, I think this is better than open and closes streams constantly.
Next, I receive the "NSStreamEventHasBytesAvailable" event on the slave device, the piece of code where handle this is:
case NSStreamEventHasBytesAvailable:
/*I can't to start a case without a expression, why not?*/
NSLog(#"[ APP ] stream handleEvent NSStreamEventHasBytesAvailable");
NSUInteger bytesRead;
uint8_t buffer[BUFFER_SIZE];
while ([_inputStream hasBytesAvailable])
{
bytesRead = [_inputStream read:buffer maxLength:BUFFER_SIZE];
NSLog(#"[ APP ] bytes read: %i", bytesRead);
if(bytesRead)
[data appendBytes:(const void *)buffer length:sizeof(buffer)];
}
[_client writeImageWithData:data];
break;
The value of BUFFER_SIZE is 32768.
I think the while block is not necessary, but I use it because if I can't read all available bytes at first iteration, I can read in the next.
So, this is the point, the stream comes correctly but the image serialized on NSData seems be corrupted, in the next, I just send data to client...
[_client writeImageWithData:data];
... and create a UIImage with data in client class simple like this...
[camPreview setImage:[UIImage imageWithData:data]];
In the camPreview (yes is a UIImageView), I have a image just to display the placeholder on the screen, when I get the imagem from network and pass to camPreview, the placeholder gets blank.
Other think is about the output, when I start the capture, first parts where I receive data, I get this message from system:
Error: ImageIO: JPEG Corrupt JPEG data: 28 extraneous bytes before marker 0xbf
Error: ImageIO: JPEG Unsupported marker type 0xbf
After some little time, I get this messages anymore.
The point is find the cause of the image not are displayed on the "slave" device.
Thanks.

Answer 1

I am not sure how often you are sending images, but even if it is not very often I think I would scan for the SOI and EOI markers in the JPEG data to insure you have all the data. Here is a post I quickly found

Answer 2

I found a answer to check jpeg format before render.
This resolved my problem and now I can display video capture from a "master" ios device to a "slave" ios device.