mac采集视频底层源码分析，调用mac os摄像头采集接口：
/*
* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#if !defined(__has_feature) || !__has_feature(objc_arc)
#error "This file requires ARC support."
#endif
#import <AVFoundation/AVFoundation.h>
#ifdef WEBRTC_IOS
#import <UIKit/UIKit.h>
#endif
#import "modules/video_capture/objc/device_info_objc.h"
#import "modules/video_capture/objc/rtc_video_capture_objc.h"
#include "rtc_base/logging.h"
using namespace webrtc;
using namespace webrtc::videocapturemodule;
@interface RTCVideoCaptureIosObjC (hidden)
- (int)changeCaptureInputWithName:(NSString*)captureDeviceName;
@end
@implementation RTCVideoCaptureIosObjC {
webrtc::videocapturemodule::VideoCaptureIos* _owner;
webrtc::VideoCaptureCapability _capability;
AVCaptureSession* _captureSession;
BOOL _orientationHasChanged;
AVCaptureConnection* _connection;
BOOL _captureChanging; // Guarded by _captureChangingCondition.
NSCondition* _captureChangingCondition;
}
@synthesize frameRotation = _framRotation;
- (id)initWithOwner:(VideoCaptureIos*)owner {
if (self = [super init]) {
_owner = owner;
_captureSession = [[AVCaptureSession alloc] init];
#if defined(WEBRTC_IOS)
_captureSession.usesApplicationAudioSession = NO;
#endif
_captureChanging = NO;
_captureChangingCondition = [[NSCondition alloc] init];
if (!_captureSession || !_captureChangingCondition) {
return nil;
}
// create and configure a new output (using callbacks)
AVCaptureVideoDataOutput* captureOutput = [[AVCaptureVideoDataOutput alloc] init];
NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey;
NSNumber* val = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_422YpCbCr8];
NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:val forKey:key];
captureOutput.videoSettings = videoSettings;
// add new output
if ([_captureSession canAddOutput:captureOutput]) {
[_captureSession addOutput:captureOutput];
} else {
RTC_LOG(LS_ERROR) << __FUNCTION__ << ": Could not add output to AVCaptureSession";
}
#ifdef WEBRTC_IOS
[[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
NSNotificationCenter* notify = [NSNotificationCenter defaultCenter];
[notify addObserver:self
selector:@selector(onVideoError:)
name:AVCaptureSessionRuntimeErrorNotification
object:_captureSession];
[notify addObserver:self
selector:@selector(deviceOrientationDidChange:)
name:UIDeviceOrientationDidChangeNotification
object:nil];
#endif
}
return self;
}
- (void)directOutputToSelf {
[[self currentOutput]
setSampleBufferDelegate:self
queue:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)];
}
- (void)directOutputToNil {
[[self currentOutput] setSampleBufferDelegate:nil queue:NULL];
}
- (void)deviceOrientationDidChange:(NSNotification*)notification {
_orientationHasChanged = YES;
[self setRelativeVideoOrientation];
}
- (void)dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
- (BOOL)setCaptureDeviceByUniqueId:(NSString*)uniqueId {
[self waitForCaptureChangeToFinish];
// check to see if the camera is already set
if (_captureSession) {
NSArray* currentInputs = [NSArray arrayWithArray:[_captureSession inputs]];
if ([currentInputs count] > 0) {
AVCaptureDeviceInput* currentInput = [currentInputs objectAtIndex:0];
if ([uniqueId isEqualToString:[currentInput.device localizedName]]) {
return YES;
}
}
}
return [self changeCaptureInputByUniqueId:uniqueId];
}
- (BOOL)startCaptureWithCapability:(const VideoCaptureCapability&)capability {
[self waitForCaptureChangeToFinish];
if (!_captureSession) {
return NO;
}
// check limits of the resolution
if (capability.maxFPS < 0 || capability.maxFPS > 60) {
return NO;
}
if ([_captureSession canSetSessionPreset:AVCaptureSessionPreset1280x720]) {
if (capability.width > 1280 || capability.height > 720) {
return NO;
}
} else if ([_captureSession canSetSessionPreset:AVCaptureSessionPreset640x480]) {
if (capability.width > 640 || capability.height > 480) {
return NO;
}
} else if ([_captureSession canSetSessionPreset:AVCaptureSessionPreset352x288]) {
if (capability.width > 352 || capability.height > 288) {
return NO;
}
} else if (capability.width < 0 || capability.height < 0) {
return NO;
}
_capability = capability;
AVCaptureVideoDataOutput* currentOutput = [self currentOutput];
if (!currentOutput) return NO;
[self directOutputToSelf];
_orientationHasChanged = NO;
_captureChanging = YES;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self startCaptureInBackgroundWithOutput:currentOutput];
});
return YES;
}
- (AVCaptureVideoDataOutput*)currentOutput {
return [[_captureSession outputs] firstObject];
}
- (void)startCaptureInBackgroundWithOutput:(AVCaptureVideoDataOutput*)currentOutput {
NSString* captureQuality = [NSString stringWithString:AVCaptureSessionPresetLow];
if (_capability.width >= 1280 || _capability.height >= 720) {
captureQuality = [NSString stringWithString:AVCaptureSessionPreset1280x720];
} else if (_capability.width >= 640 || _capability.height >= 480) {
captureQuality = [NSString stringWithString:AVCaptureSessionPreset640x480];
} else if (_capability.width >= 352 || _capability.height >= 288) {
captureQuality = [NSString stringWithString:AVCaptureSessionPreset352x288];
}
// begin configuration for the AVCaptureSession
[_captureSession beginConfiguration];
// picture resolution
[_captureSession setSessionPreset:captureQuality];
_connection = [currentOutput connectionWithMediaType:AVMediaTypeVideo];
[self setRelativeVideoOrientation];
// finished configuring, commit settings to AVCaptureSession.
[_captureSession commitConfiguration];
[_captureSession startRunning];
[self signalCaptureChangeEnd];
}
- (void)setRelativeVideoOrientation {
if (!_connection.supportsVideoOrientation) {
return;
}
#ifndef WEBRTC_IOS
_connection.videoOrientation = AVCaptureVideoOrientationLandscapeRight;
return;
#else
switch ([UIDevice currentDevice].orientation) {
case UIDeviceOrientationPortrait:
_connection.videoOrientation = AVCaptureVideoOrientationPortrait;
break;
case UIDeviceOrientationPortraitUpsideDown:
_connection.videoOrientation = AVCaptureVideoOrientationPortraitUpsideDown;
break;
case UIDeviceOrientationLandscapeLeft:
_connection.videoOrientation = AVCaptureVideoOrientationLandscapeRight;
break;
case UIDeviceOrientationLandscapeRight:
_connection.videoOrientation = AVCaptureVideoOrientationLandscapeLeft;
break;
case UIDeviceOrientationFaceUp:
case UIDeviceOrientationFaceDown:
case UIDeviceOrientationUnknown:
if (!_orientationHasChanged) {
_connection.videoOrientation = AVCaptureVideoOrientationPortrait;
}
break;
}
#endif
}
- (void)onVideoError:(NSNotification*)notification {
NSLog(@"onVideoError: %@", notification);
// TODO(sjlee): make the specific error handling with this notification.
RTC_LOG(LS_ERROR) << __FUNCTION__ << ": [AVCaptureSession startRunning] error.";
}
- (BOOL)stopCapture {
#ifdef WEBRTC_IOS
[[UIDevice currentDevice] endGeneratingDeviceOrientationNotifications];
#endif
_orientationHasChanged = NO;
[self waitForCaptureChangeToFinish];
[self directOutputToNil];
if (!_captureSession) {
return NO;
}
_captureChanging = YES;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void) {
[self stopCaptureInBackground];
});
return YES;
}
- (void)stopCaptureInBackground {
[_captureSession stopRunning];
[self signalCaptureChangeEnd];
}
- (BOOL)changeCaptureInputByUniqueId:(NSString*)uniqueId {
[self waitForCaptureChangeToFinish];
NSArray* currentInputs = [_captureSession inputs];
// remove current input
if ([currentInputs count] > 0) {
AVCaptureInput* currentInput = (AVCaptureInput*)[currentInputs objectAtIndex:0];
[_captureSession removeInput:currentInput];
}
// Look for input device with the name requested (as our input param)
// get list of available capture devices
int captureDeviceCount = [DeviceInfoIosObjC captureDeviceCount];
if (captureDeviceCount <= 0) {
return NO;
}
AVCaptureDevice* captureDevice = [DeviceInfoIosObjC captureDeviceForUniqueId:uniqueId];
if (!captureDevice) {
return NO;
}
// now create capture session input out of AVCaptureDevice
NSError* deviceError = nil;
AVCaptureDeviceInput* newCaptureInput =
[AVCaptureDeviceInput deviceInputWithDevice:captureDevice error:&deviceError];
if (!newCaptureInput) {
const char* errorMessage = [[deviceError localizedDescription] UTF8String];
RTC_LOG(LS_ERROR) << __FUNCTION__ << ": deviceInputWithDevice error:" << errorMessage;
return NO;
}
// try to add our new capture device to the capture session
[_captureSession beginConfiguration];
BOOL addedCaptureInput = NO;
if ([_captureSession canAddInput:newCaptureInput]) {
[_captureSession addInput:newCaptureInput];
addedCaptureInput = YES;
} else {
addedCaptureInput = NO;
}
[_captureSession commitConfiguration];
return addedCaptureInput;
}
- (void)captureOutput:(AVCaptureOutput*)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection*)connection {
const int kFlags = 0;
CVImageBufferRef videoFrame = CMSampleBufferGetImageBuffer(sampleBuffer);
if (CVPixelBufferLockBaseAddress(videoFrame, kFlags) != kCVReturnSuccess) {
return;
}
uint8_t* baseAddress = (uint8_t*)CVPixelBufferGetBaseAddress(videoFrame);
const size_t width = CVPixelBufferGetWidth(videoFrame);
const size_t height = CVPixelBufferGetHeight(videoFrame);
const size_t frameSize = width * height * 2;
VideoCaptureCapability tempCaptureCapability;
tempCaptureCapability.width = width;
tempCaptureCapability.height = height;
tempCaptureCapability.maxFPS = _capability.maxFPS;
tempCaptureCapability.videoType = VideoType::kUYVY;
_owner->IncomingFrame(baseAddress, frameSize, tempCaptureCapability, 0);
CVPixelBufferUnlockBaseAddress(videoFrame, kFlags);
}
- (void)signalCaptureChangeEnd {
[_captureChangingCondition lock];
_captureChanging = NO;
[_captureChangingCondition signal];
[_captureChangingCondition unlock];
}
- (void)waitForCaptureChangeToFinish {
[_captureChangingCondition lock];
while (_captureChanging) {
[_captureChangingCondition wait];
}
[_captureChangingCondition unlock];
}
@end
rtc_video_capture_obj.h：
/*
* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef MODULES_VIDEO_CAPTURE_OBJC_RTC_VIDEO_CAPTURE_OBJC_H_
#define MODULES_VIDEO_CAPTURE_OBJC_RTC_VIDEO_CAPTURE_OBJC_H_
#import <Foundation/Foundation.h>
#ifdef WEBRTC_IOS
#import <UIKit/UIKit.h>
#endif
#include "modules/video_capture/objc/video_capture.h"
// The following class listens to a notification with name:
// 'StatusBarOrientationDidChange'.
// This notification must be posted in order for the capturer to reflect the
// orientation change in video w.r.t. the application orientation.
@interface RTCVideoCaptureIosObjC
: NSObject<AVCaptureVideoDataOutputSampleBufferDelegate>
@property webrtc::VideoRotation frameRotation;
// custom initializer. Instance of VideoCaptureIos is needed
// for callback purposes.
// default init methods have been overridden to return nil.
- (id)initWithOwner:(webrtc::videocapturemodule::VideoCaptureIos*)owner;
- (BOOL)setCaptureDeviceByUniqueId:(NSString*)uniqueId;
- (BOOL)startCaptureWithCapability:
(const webrtc::VideoCaptureCapability&)capability;
- (BOOL)stopCapture;
@end
#endif // MODULES_VIDEO_CAPTURE_OBJC_RTC_VIDEO_CAPTURE_OBJC_H_