尽管StackOverflow上有很好的信息,我仍然在这里,
我正在为iPad 2上的视频编写一个OpenGL渲染缓冲区(使用iOS 4.3).这正是我正在尝试的：
A)设置一个AVAssetWriterInputPixelBufferAdaptor
>创建一个指向视频文件的AVAssetWriter
>使用适当的设置设置AVAssetWriterInput
>设置一个AVAssetWriterInputPixelBufferAdaptor将数据添加到视频文件
B)使用该AVAssetWriterInputPixelBufferAdaptor将数据写入视频文件
将OpenGL代码渲染到屏幕
>通过glReadPixels获取OpenGL缓冲区
>从OpenGL数据创建一个CVPixelBufferRef
>使用appendPixelBuffer方法将PixelBuffer附加到AVAssetWriterInputPixelBufferAdaptor
但是,我有这样做的问题.我现在的策略是在按下按钮时设置AVAssetWriterInputPixelBufferAdaptor.一旦AVAssetWriterInputPixelBufferAdaptor有效,我设置一个标志来发信号EAGLView创建一个像素缓冲区,并通过appendPixelBuffer将其附加到视频文件中,以获得给定的帧数.
现在我的代码崩溃,因为它试图附加第二个像素缓冲区,给我以下错误：
-[__NSCFDictionary appendPixelBuffer:withPresentationTime:]: unrecognized selector sent to instance 0x131db0
这是我的AVAsset设置代码(很多是基于Rudy Aramayo的代码,它在正常图像上工作,但不是为纹理设置的)：
- (void) testVideoWriter {
//initialize global info
MOVIE_NAME = @"Documents/Movie.mov";
CGSize size = CGSizeMake(480,320);
frameLength = CMTimeMake(1,5);
currentTime = kCMTimeZero;
currentFrame = 0;
NSString *MOVIE_PATH = [NSHomeDirectory() stringByAppendingPathComponent:MOVIE_NAME];
NSError *error = nil;
unlink([betaCompressionDirectory UTF8String]);
videoWriter = [[AVAssetWriter alloc] initWithURL:[NSURL fileURLWithPath:betaCompressionDirectory] fileType:AVFileTypeQuickTimeMovie error:&error];
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:AVVideoCodecH264,AVVideoCodecKey,[NSNumber numberWithInt:size.width],AVVideoWidthKey,[NSNumber numberWithInt:size.height],AVVideoHeightKey,nil];
writerInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];
//writerInput.expectsMediaDataInRealTime = NO;
NSDictionary *sourcePixelBufferAttributesDictionary = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA],kCVPixelBufferPixelFormatTypeKey,nil];
adaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput sourcePixelBufferAttributes:sourcePixelBufferAttributesDictionary];
[adaptor retain];
[videoWriter addInput:writerInput];
[videoWriter startWriting];
[videoWriter startSessionAtSourceTime:kCMTimeZero];
VIDEO_WRITER_IS_READY = true;
}
好的,现在我的videoWriter和适配器设置好了,我告诉我的OpenGL渲染器为每个帧创建一个像素缓冲区：
- (void) captureScreenVideo {
if (!writerInput.readyForMoreMediaData) {
return;
}
CGSize esize = CGSizeMake(eagl.backingWidth,eagl.backingHeight);
NSInteger myDataLength = esize.width * esize.height * 4;
GLuint *buffer = (GLuint *) malloc(myDataLength);
glReadPixels(0,esize.width,esize.height,GL_RGBA,GL_UNSIGNED_BYTE,buffer);
CVPixelBufferRef pixel_buffer = NULL;
CVPixelBufferCreateWithBytes (NULL,kCVPixelFormatType_32BGRA,buffer,4 * esize.width,NULL,&pixel_buffer);
/* DON'T FREE THIS BEFORE USING pixel_buffer! */
//free(buffer);
if(![adaptor appendPixelBuffer:pixel_buffer withPresentationTime:currentTime]) {
NSLog(@"FAIL");
} else {
NSLog(@"Success:%d",currentFrame);
currentTime = CMTimeAdd(currentTime,frameLength);
}
free(buffer);
CVPixelBufferRelease(pixel_buffer);
}
currentFrame++;
if (currentFrame > MAX_FRAMES) {
VIDEO_WRITER_IS_READY = false;
[writerInput markAsFinished];
[videoWriter finishWriting];
[videoWriter release];
[self moveVideoToSavedPhotos];
}
}
最后,我将视频移动到相机卷：
- (void) moveVideoToSavedPhotos {
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
NSString *localVid = [NSHomeDirectory() stringByAppendingPathComponent:MOVIE_NAME];
NSURL* fileURL = [NSURL fileURLWithPath:localVid];
[library writeVideoAtPathToSavedPhotosAlbum:fileURL
completionBlock:^(NSURL *assetURL,NSError *error) {
if (error) {
NSLog(@"%@: Error saving context: %@",[self class],[error localizedDescription]);
}
}];
[library release];
}
但是,正如我所说,我正在打电话给appendPixelBuffer.
对不起,发送这么多的代码,但我真的不知道我做错了什么.更新将图像写入视频的项目似乎是微不足道的,但是我无法通过glReadPixels创建像素缓冲区并附加它.这让我疯狂！如果任何人有任何建议或OpenGL的工作代码示例 – >视频将是惊人的…谢谢！
解决方法
我刚刚得到类似于这个在我的开源
GPUImage框架中工作的东西,基于上面的代码,所以我以为我会提供我的工作解决方案.在我的情况下,我可以像Srikumar一样使用像素缓冲池,而不是为每个帧手动创建的像素缓冲区.
我首先配置要录制的电影：
NSError *error = nil;
assetWriter = [[AVAssetWriter alloc] initWithURL:movieURL fileType:AVFileTypeAppleM4V error:&error];
if (error != nil)
{
NSLog(@"Error: %@",error);
}
NSMutableDictionary * outputSettings = [[NSMutableDictionary alloc] init];
[outputSettings setObject: AVVideoCodecH264 forKey: AVVideoCodecKey];
[outputSettings setObject: [NSNumber numberWithInt: videoSize.width] forKey: AVVideoWidthKey];
[outputSettings setObject: [NSNumber numberWithInt: videoSize.height] forKey: AVVideoHeightKey];
assetWriterVideoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:outputSettings];
assetWriterVideoInput.expectsMediaDataInRealTime = YES;
// You need to use BGRA for the video in order to get realtime encoding. I use a color-swizzling shader to line up glReadPixels' normal RGBA output with the movie input's BGRA.
NSDictionary *sourcePixelBufferAttributesDictionary = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA],[NSNumber numberWithInt:videoSize.width],kCVPixelBufferWidthKey,[NSNumber numberWithInt:videoSize.height],kCVPixelBufferHeightKey,nil];
assetWriterPixelBufferInput = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:assetWriterVideoInput sourcePixelBufferAttributes:sourcePixelBufferAttributesDictionary];
[assetWriter addInput:assetWriterVideoInput];
然后使用此代码使用glReadPixels()来抓取每个渲染的帧：
CVPixelBufferRef pixel_buffer = NULL;
CVReturn status = CVPixelBufferPoolCreatePixelBuffer (NULL,[assetWriterPixelBufferInput pixelBufferPool],&pixel_buffer);
if ((pixel_buffer == NULL) || (status != kCVReturnSuccess))
{
return;
}
else
{
CVPixelBufferLockBaseAddress(pixel_buffer,0);
GLubyte *pixelBufferData = (GLubyte *)CVPixelBufferGetBaseAddress(pixel_buffer);
glReadPixels(0,videoSize.width,videoSize.height,pixelBufferData);
}
// May need to add a check here,because if two consecutive times with the same value are added to the movie,it aborts recording
CMTime currentTime = CMTimeMakeWithSeconds([[NSDate date] timeIntervalSinceDate:startTime],120);
if(![assetWriterPixelBufferInput appendPixelBuffer:pixel_buffer withPresentationTime:currentTime])
{
NSLog(@"Problem appending pixel buffer at time: %lld",currentTime.value);
}
else
{
// NSLog(@"Recorded pixel buffer at time: %lld",currentTime.value);
}
CVPixelBufferUnlockBaseAddress(pixel_buffer,0);
CVPixelBufferRelease(pixel_buffer);
我注意到的一件事是,如果我试图附加两个具有相同整数时间值的像素缓冲区(在所提供的基础上),则整个录制将失败,输入将永远不会再占用另一个像素缓冲区.同样,如果我尝试在从池中检索后附加像素缓冲区失败,它将中止录像.因此,上述代码中的早期救助.
除了上述代码之外,我使用一个颜色调整的着色器将OpenGL ES场景中的RGBA渲染转换为BGRA,以便AVAssetWriter进行快速编码.有了这个,我可以在iPhone 4上以30 FPS录制640×480的视频.
