前言
目前是准备做一个美颜相机类的项目，这篇将介绍视频录制的一些思路。
代码已上传MagicCamera，你的star和fork是对我最好的支持和动力。
方案
大致分为两种：
- 方案一：录制成一个视频文件
优点: 单个视频文件，方便处理
缺点：不支持分段回删 - 方案二：录制成多个文件
优点：支持分段回删
缺点：需要考虑视频合成步骤
注：视频合成有多种途径
方案一
思路：计算暂停时间
GPUImageMovieWriter 中采用的就是这一种方式，大致思路如下：
// 设置暂停
- (void)setPaused:(BOOL)newValue {
if (_paused != newValue) {
_paused = newValue;
if (_paused) {
discont = YES;
}
}
}
// 新的一帧数据
if (!isRecording || _paused) // 如果是暂停状态则放弃写入
{
[firstInputFramebuffer unlock];
return;
}
if (discont) { // 恢复录制时，判断是否暂停过，重新计算时间
discont = NO;
CMTime current;
if (offsetTime.value > 0) {
current = CMTimeSubtract(frameTime, offsetTime);
} else {
current = frameTime;
}
CMTime offset = CMTimeSubtract(current, previousFrameTime);
if (offsetTime.value == 0) {
offsetTime = offset;
} else {
offsetTime = CMTimeAdd(offsetTime, offset);
}
}
if (offsetTime.value > 0) {
frameTime = CMTimeSubtract(frameTime, offsetTime);
}
方案二
思路：采用AVAssetWriter 生成多个视频文件，如果不需要对帧数据进行处理也可以采用AVCaptureMovieFileOutput
合成：
- 采用AVFoundation (合成时间不乐观)
- 采用FFmpeg(尚未尝试，速度应该会快一点，但是同样避免不了量级上的处理时间)
- 不合成(尝试中，在后续短视频编辑文章，会详细介绍)
基础 本文采用方案二
下面介绍一下视频录制需要用到的类:
-
AVCaptureSession-- 是AVFoundation捕捉视频类的中心枢纽 -
AVCaptureVideoPreviewLayer-- 是CoreAnimation里面layer的一个子类，用来做为AVCaptureSession预览视频输出 -
AVCaptureDevice-- 每个实例对应一个设备,如摄像头或麦克风。 -
AVCaptureDeviceInput-- 是AVCaptureSession输入源,提供媒体数据从设备连接到系统 -
AVCaptureConnection-- 代表AVCaptureInputPort或端口之间的连接,和一个AVCaptureOutput或AVCaptureVideoPreviewLayer在AVCaptureSession中的呈现 -
AVCaptureMovieFileOutput-- AVCaptureMovieFileOutput是AVCaptureFileOutput的子类，用来写入QuickTime视频类型的媒体文件 -
AVCaptureVideoDataOutput-- 是AVCaptureOutput一个子类，可以用于用来输出未压缩或压缩的视频捕获的帧 -
AVCaptureAudioDataOutput-- 是AVCaptureOutput的子类，可用于用来输出捕获来的非压缩或压缩的音频样本 -
AVAssetWriter-- 为写入媒体数据到一个新的文件提供服务，AVAssetWriter的实例可以规定写入媒体文件的格式，如QuickTime电影文件格式或MPEG-4文件格式等等 -
AVAssetWriterInput去拼接一个多媒体样本类型为CMSampleBuffer的实例到AVAssetWriter对象的输出文件的一个轨道
框架
实现
摄像头采集、渲染等借鉴于GPUImage，这部分可以直接采用GPUImage，文件写入部分需要自定义或者在GPUImage的基础上重新实现 GPUImageMovieWriter。
- 实现部分视频特效处理，音频暂时未处理
视频处理
- (void)processVideoSampleBuffer:(CMSampleBufferRef)sampleBuffer
{
CVImageBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
int bufferWidth = (int) CVPixelBufferGetWidth(pixelBuffer);
int bufferHeight = (int) CVPixelBufferGetHeight(pixelBuffer);
CMTime currentTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
CFTypeRef colorAttachments = CVBufferGetAttachment(pixelBuffer, kCVImageBufferYCbCrMatrixKey, NULL);
if (colorAttachments == kCVImageBufferYCbCrMatrix_ITU_R_601_4) {
if (isFullYUVRange) {
_preferredConversion = kMKColorConversion601FullRange;
}
else {
_preferredConversion = kMKColorConversion601;
}
}
else {
_preferredConversion = kMKColorConversion709;
}
// 这部分创建采集纹理，参考GPUImage。(自己实现的过程中会出现黑屏, 报错等 CVOpenGLESTextureCacheCreateTextureFromImage failed (error: -6683))
[_myContext useAsCurrentContext];
if ([MKGPUImageContext supportsFastTextureUpload]) {
if (CVPixelBufferGetPlaneCount(pixelBuffer) > 0) { // Check for YUV planar inputs to do RGB conversion
CVPixelBufferLockBaseAddress(pixelBuffer, 0);
CVOpenGLESTextureRef _luminanceTextureRef;
CVOpenGLESTextureRef _chrominanceTextureRef;
if ( (imageBufferWidth != bufferWidth) && (imageBufferHeight != bufferHeight) )
{
imageBufferWidth = bufferWidth;
imageBufferHeight = bufferHeight;
}
CVReturn err;
// Y-plane
glActiveTexture(GL_TEXTURE4);
err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, [_myContext coreVideoTextureCache], pixelBuffer, NULL, GL_TEXTURE_2D, GL_LUMINANCE, bufferWidth, bufferHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, 0, &_luminanceTextureRef);
if (err)
{
NSLog(@"Error at CVOpenGLESTextureCacheCreateTextureFromImage %d", err);
}
luminanceTexture = CVOpenGLESTextureGetName(_luminanceTextureRef);
glBindTexture(GL_TEXTURE_2D, luminanceTexture);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
// UV-plane
glActiveTexture(GL_TEXTURE5);
err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, [_myContext coreVideoTextureCache], pixelBuffer, NULL, GL_TEXTURE_2D, GL_LUMINANCE_ALPHA, bufferWidth/2, bufferHeight/2, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, 1, &_chrominanceTextureRef);
if (err)
{
NSLog(@"Error at CVOpenGLESTextureCacheCreateTextureFromImage %d", err);
}
chrominanceTexture = CVOpenGLESTextureGetName(_chrominanceTextureRef);
glBindTexture(GL_TEXTURE_2D, chrominanceTexture);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
[self convertYUVToRGBOutput];
if (MKGPUImageRotationSwapsWidthAndHeight(internalRotation))
{
imageBufferWidth = bufferHeight;
imageBufferHeight = bufferWidth;
}
CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
CFRelease(_luminanceTextureRef);
CFRelease(_chrominanceTextureRef);
textureId = [_outputFramebuffer texture];
}
} else {
CVPixelBufferLockBaseAddress(pixelBuffer, 0);
int bytesPerRow = (int) CVPixelBufferGetBytesPerRow(pixelBuffer);
MKGPUTextureOptions options;
options.minFilter = GL_LINEAR;
options.magFilter = GL_LINEAR;
options.wrapS = GL_CLAMP_TO_EDGE;
options.wrapT = GL_CLAMP_TO_EDGE;
options.internalFormat = GL_RGBA;
options.format = GL_BGRA;
options.type = GL_UNSIGNED_BYTE;
_outputFramebuffer = [[_myContext framebufferCache] fetchFramebufferForSize:CGSizeMake(bytesPerRow/4, bufferHeight) textureOptions:options missCVPixelBuffer:YES];
[_outputFramebuffer activateFramebuffer];
glBindTexture(GL_TEXTURE_2D, [_outputFramebuffer texture]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, bytesPerRow / 4, bufferHeight, 0, GL_BGRA, GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddress(pixelBuffer));
textureId = [_outputFramebuffer texture];
imageBufferWidth = bytesPerRow / 4;
imageBufferHeight = bufferHeight;
CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
}
int rotatedImageBufferWidth = bufferWidth, rotatedImageBufferHeight = bufferHeight;
if (GPUImageRotationSwapsWidthAndHeight(internalRotation))
{
rotatedImageBufferWidth = bufferHeight;
rotatedImageBufferHeight = bufferWidth;
}
// 特效处理
if ([self.delegate respondsToSelector:@selector(effectsProcessingTexture:inputSize:rotateMode:)]) {
[self.delegate effectsProcessingTexture:textureId inputSize:CGSizeMake(imageBufferWidth, imageBufferHeight) rotateMode:outputRotation];
}
// 写入处理过的视频帧
[_segmentMovieWriter processVideoTextureId:textureId AtRotationMode:outputRotation AtTime:currentTime];
// 渲染
if ([self.delegate respondsToSelector:@selector(renderTexture:inputSize:rotateMode:)]) {
[self.delegate renderTexture:textureId inputSize:CGSizeMake(rotatedImageBufferWidth, rotatedImageBufferHeight) rotateMode:outputRotation];
}
[_outputFramebuffer unlock];
_outputFramebuffer = nil;
}
文件写入
- (void)startWriting {
dispatch_async(dispatch_get_global_queue(0, 0), ^{
NSError *error = nil;
NSString *fileType = AVFileTypeQuickTimeMovie;
self.assetWriter = [AVAssetWriter assetWriterWithURL:[self outputURL]
fileType:fileType
error:&error];
if (!self.assetWriter || error) {
NSString *formatString = @"Could not create AVAssetWriter: %@";
NSLog(@"%@", [NSString stringWithFormat:formatString, error]);
return;
}
// use default output settings if none specified
if (_videoSettings == nil) {
NSMutableDictionary *settings = [[NSMutableDictionary alloc] init];
[settings setObject:AVVideoCodecH264 forKey:AVVideoCodecKey];
[settings setObject:[NSNumber numberWithInt:videoSize.width] forKey:AVVideoWidthKey];
[settings setObject:[NSNumber numberWithInt:videoSize.height] forKey:AVVideoHeightKey];
_videoSettings = settings;
} else { // custom output settings specified
__unused NSString *videoCodec = [_videoSettings objectForKey:AVVideoCodecKey];
__unused NSNumber *width = [_videoSettings objectForKey:AVVideoWidthKey];
__unused NSNumber *height = [_videoSettings objectForKey:AVVideoHeightKey];
NSAssert(videoCodec && width && height, @"OutputSettings is missing required parameters.");
if( [_videoSettings objectForKey:@"EncodingLiveVideo"] ) {
NSMutableDictionary *tmp = [_videoSettings mutableCopy];
[tmp removeObjectForKey:@"EncodingLiveVideo"];
_videoSettings = tmp;
}
}
self.assetWriterVideoInput = [[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeVideo
outputSettings:self.videoSettings];
self.assetWriterVideoInput.expectsMediaDataInRealTime = YES;
NSDictionary *sourcePixelBufferAttributesDictionary = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA], kCVPixelBufferPixelFormatTypeKey,
[NSNumber numberWithInt:videoSize.width], kCVPixelBufferWidthKey,
[NSNumber numberWithInt:videoSize.height], kCVPixelBufferHeightKey,
nil];
self.assetWriterInputPixelBufferAdaptor = [[AVAssetWriterInputPixelBufferAdaptor alloc] initWithAssetWriterInput:self.assetWriterVideoInput sourcePixelBufferAttributes:sourcePixelBufferAttributesDictionary];
if ([self.assetWriter canAddInput:self.assetWriterVideoInput]) {
[self.assetWriter addInput:self.assetWriterVideoInput];
} else {
NSLog(@"Unable to add video input.");
return;
}
self.assetWriterAudioInput =
[[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeAudio
outputSettings:self.audioSettings];
self.assetWriterAudioInput.expectsMediaDataInRealTime = YES;
if ([self.assetWriter canAddInput:self.assetWriterAudioInput]) {
[self.assetWriter addInput:self.assetWriterAudioInput];
} else {
NSLog(@"Unable to add audio input.");
}
runMSynchronouslyOnContextQueue(myContext, ^{
[self.assetWriter startWriting];
});
self.isWriting = YES;
self.firstSample = YES;
});
}
效果
