我正在通过渲染 OpenGL 纹理生成电影。生成的影片的某些帧看起来没有完全渲染，因为它们显示了前一帧的一部分。如果我添加一个 NSThread [NSThread sleepForTimeInterval:0.05]; 问题没有出现，但我不能依赖这个指令。
这是没有 [NSThread sleepForTimeInterval:0.05] 的结果
这是添加 [NSThread sleepForTimeInterval:0.05] 时的结果
我使用的代码是：
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^
{
//Video writer
AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:
[NSURL fileURLWithPath:tempVideoPath]
fileType:AVFileTypeQuickTimeMovie
error:&error];
NSParameterAssert(videoWriter);
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
[NSNumber numberWithInt:MOVsize.width], AVVideoWidthKey,
[NSNumber numberWithInt:MOVsize.height], AVVideoHeightKey,
nil];
AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput
assetWriterInputWithMediaType:AVMediaTypeVideo
outputSettings:videoSettings];
videoWriterInput.expectsMediaDataInRealTime=NO;
NSParameterAssert(videoWriterInput);
NSParameterAssert([videoWriter canAddInput:videoWriterInput]);
[videoWriter addInput:videoWriterInput];
NSDictionary* pixelAttributesDict;
pixelAttributesDict= [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA], kCVPixelBufferPixelFormatTypeKey,
[NSNumber numberWithInt:1024], kCVPixelBufferWidthKey,
[NSNumber numberWithInt:768], kCVPixelBufferHeightKey,
nil];
AVAssetWriterInputPixelBufferAdaptor* adaptor=[AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:videoWriterInput sourcePixelBufferAttributes:pixelAttributesDict];
[videoWriter startWriting];
[videoWriter startSessionAtSourceTime:kCMTimeZero];
if([EAGLContext currentContext]!= glContext)
[EAGLContext setCurrentContext:glContext];
[self createDataFBO:adaptor];
for (int frame=0;frame<samplesNumber;frame++){
while (!videoWriterInput.readyForMoreMediaData)
{
NSDate *maxDate = [NSDate dateWithTimeIntervalSinceNow:0.1];
[[NSRunLoop currentRunLoop] runUntilDate:maxDate];
}
//glBindFramebuffer(GL_FRAMEBUFFER, movieFramebuffer);
//Render current frame with openGL
[self renderFrameAt:frame];
CVReturn lockResult= CVPixelBufferLockBaseAddress(renderTarget, 0);
BOOL test =(lockResult==kCVReturnSuccess) && [adaptor appendPixelBuffer:renderTarget withPresentationTime:CMTimeMake(frame, kFps)];
if(!test) {
NSLog(@"append failed!");
}
// 如果我在这里添加 [NSThread sleepForTimeInterval:0.05]; 渲染效果很好
CVPixelBufferUnlockBaseAddress(renderTarget, 0);
dispatch_async(dispatch_get_main_queue(), ^
{
[self updateProgressBar];
});
}
[videoWriterInput markAsFinished];
[videoWriter endSessionAtSourceTime:CMTimeMake(samplesNumber, kFps)];
[videoWriter finishWritingWithCompletionHandler:^{
[self destroyDataFBO];
//End of movie generation
}];
});
}
这是我用来创建纹理缓存的代码
- (void)createDataFBO:(AVAssetWriterInputPixelBufferAdaptor *) adaptor;
{
glActiveTexture(GL_TEXTURE1);
glGenFramebuffers(1, &movieFramebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, movieFramebuffer);
#if defined(__IPHONE_6_0)
CVReturn err = CVOpenGLESTextureCacheCreate(kCFAllocatorDefault, NULL, [EAGLContext currentContext], NULL, &coreVideoTextureCache);
#else
CVReturn err = CVOpenGLESTextureCacheCreate(kCFAllocatorDefault, NULL, (__bridge void *)[EAGLContext currentContext], NULL, &coreVideoTextureCache);
#endif
if (err)
{
NSAssert(NO, @"Error at CVOpenGLESTextureCacheCreate %d", err);
}
// Code originally sourced from http://allmybrain.com/2011/12/08/rendering-to-a-texture-with-ios-5-texture-cache-api/
CVPixelBufferPoolCreatePixelBuffer (NULL, [adaptor pixelBufferPool], &renderTarget);
size_t frameWidth = CVPixelBufferGetWidth(renderTarget);
size_t frameHeight = CVPixelBufferGetHeight(renderTarget);
CVOpenGLESTextureCacheCreateTextureFromImage (kCFAllocatorDefault, coreVideoTextureCache, renderTarget,
NULL, // texture attributes
GL_TEXTURE_2D,
GL_RGBA, // opengl format
frameWidth,
frameHeight,
GL_BGRA, // native iOS format
GL_UNSIGNED_BYTE,
0,
&renderTexture);
glBindTexture(CVOpenGLESTextureGetTarget(renderTexture), CVOpenGLESTextureGetName(renderTexture));
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, CVOpenGLESTextureGetName(renderTexture), 0);
GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
NSAssert(status == GL_FRAMEBUFFER_COMPLETE, @"Incomplete filter FBO: %d", status);
}