长时间潜伏，第一次海报。
我正在尝试解码视频并将每个帧保存为图像。 （该视频是我之前录制的视频，可在iPhone上正常播放。）我的第一步是确保我获得正确的图像数据，所以这个小片段只是在UIImageView中显示：
- (void)showFrame:(UIImage*)frame {
self.videoIV.image=frame;
}
- (void)unarchiveThread:(NSString*)fileName {
NSAutoreleasePool *pool=[[NSAutoreleasePool alloc] init];
AVURLAsset *asset = [[[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:fileName] options:nil] autorelease];
if (asset==nil) {
NSLog(@"Couldn't load avasset from '%@'\n",fileName);
return;
}
AVAssetReader *reader=[[[AVAssetReader alloc] initWithAsset:asset error:NULL] autorelease];
NSArray* video_tracks = [asset tracksWithMediaType:AVMediaTypeVideo];
AVAssetTrack* video_track = [video_tracks objectAtIndex:0];
CGAffineTransform transform=video_track.preferredTransform;
NSDictionary* dictionary = [NSDictionary dictionaryWithObject:@(kCVPixelFormatType_32BGRA) forKey:(NSString*)kCVPixelBufferPixelFormatTypeKey];
AVAssetReaderTrackOutput* asset_reader_output = [[[AVAssetReaderTrackOutput alloc] initWithTrack:video_track outputSettings:dictionary] autorelease];
[reader addOutput:asset_reader_output];
[reader startReading];
CMSampleBufferRef buffer;
while ([reader status]==AVAssetReaderStatusReading ) {
buffer = [asset_reader_output copyNextSampleBuffer];
if (buffer!=NULL) {
NSLog(@"buffer=%@",buffer);
CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(buffer);
NSLog(@"pixel buffer=%@",pixelBuffer);
CIImage *cImage = [CIImage imageWithCVPixelBuffer:pixelBuffer];
NSLog(@"cImage = %@",cImage);
cImage=[cImage imageByApplyingTransform:transform];
NSLog(@"transformed cImage = %@",cImage);
UIImage *image=[UIImage imageWithCIImage:cImage];
NSLog(@"image=%@",image);
[self performSelectorOnMainThread:@selector(showFrame:) withObject:image waitUntilDone:YES];
CMSampleBufferInvalidate(buffer);
CFRelease(buffer);
buffer = nil;
}
}
[pool drain];
}
前两个步骤工作正常（我得到一个有效的缓冲区和像素缓冲区）但cIImage:imageWithCVPixelBuffer:由于某种原因（get（null））不起作用。这是我的输出：
buffer=CMSampleBuffer 0xba6e2d0 retainCount: 1 allocator: 0x4b43e7
invalid = NO
dataReady = YES
makeDataReadyCallback = 0x0
makeDataReadyRefcon = 0x0
formatDescription = <CMVideoFormatDescription 0xba6e260 [0x212eb48]> {
mediaType:'vide'
mediaSubType:'BGRA'
mediaSpecific: {
codecType: 'BGRA' dimensions: 1920 x 1080
}
extensions: {<CFBasicHash 0xba6e2a0 [0x212eb48]>{type = immutable dict, count = 5,
entries =>
2 : <CFString 0x4c0024 [0x212eb48]>{contents = "Version"} = <CFNumber 0xb8682b0 [0x212eb48]>{value = +2, type = kCFNumberSInt32Type}
3 : <CFString 0x4bffe4 [0x212eb48]>{contents = "CVBytesPerRow"} = <CFNumber 0xba6e1f0 [0x212eb48]>{value = +7680, type = kCFNumberSInt32Type}
4 : <CFString 0x466f1c [0x212eb48]>{contents = "CVImageBufferYCbCrMatrix"} = <CFString 0x466f2c [0x212eb48]>{contents = "ITU_R_709_2"}
5 : <CFString 0x466f5c [0x212eb48]>{contents = "CVImageBufferColorPrimaries"} = <CFString 0x466f2c [0x212eb48]>{contents = "ITU_R_709_2"}
6 : <CFString 0x466f8c [0x212eb48]>{contents = "CVImageBufferTransferFunction"} = <CFString 0x466f2c [0x212eb48]>{contents = "ITU_R_709_2"}
}
}
}
sbufToTrackReadiness = 0x0
numSamples = 1
sampleTimingArray[1] = {
{PTS = {0/600 = 0.000}, DTS = {INVALID}, duration = {INVALID}},
}
imageBuffer = 0xba6dff0
pixel buffer=<CVPixelBuffer 0xba6dff0 width=1920 height=1080 bytesPerRow=7680 pixelFormat=BGRA attributes=<CFBasicHash 0xba6de30 [0x212eb48]>{type = immutable dict, count = 3,
entries =>
0 : <CFString 0x466cdc [0x212eb48]>{contents = "Height"} = <CFNumber 0x8e70ec0 [0x212eb48]>{value = +1080, type = kCFNumberSInt32Type}
1 : <CFString 0x466ccc [0x212eb48]>{contents = "Width"} = <CFNumber 0x8e70eb0 [0x212eb48]>{value = +1920, type = kCFNumberSInt32Type}
2 : <CFString 0x46707c [0x212eb48]>{contents = "PixelFormatType"} = <CFNumber 0xbb89710 [0x212eb48]>{value = +1111970369, type = kCFNumberSInt32Type}
}
propagatedAttachments=<CFBasicHash 0xba6e110 [0x212eb48]>{type = mutable dict, count = 3,
entries =>
0 : <CFString 0x466f1c [0x212eb48]>{contents = "CVImageBufferYCbCrMatrix"} = <CFString 0x466f2c [0x212eb48]>{contents = "ITU_R_709_2"}
1 : <CFString 0x466f8c [0x212eb48]>{contents = "CVImageBufferTransferFunction"} = <CFString 0x466f2c [0x212eb48]>{contents = "ITU_R_709_2"}
2 : <CFString 0x466f5c [0x212eb48]>{contents = "CVImageBufferColorPrimaries"} = <CFString 0x466f2c [0x212eb48]>{contents = "ITU_R_709_2"}
}
nonPropagatedAttachments=<CFBasicHash 0xba6dce0 [0x212eb48]>{type = mutable dict, count = 0,
entries =>
}
iosurface=0x0>
cImage = (null)
transformed cImage = (null)
image=<UIImage: 0x8c669d0>
任何人都知道我做错了什么？我搜索了Stack Overflow，发现了很多这样的例子（来自实时订阅源），但没有使用AVAssetReader，然后将缓冲区从copyNextSampleBuffer转换为CIImage。
答案 0 :(得分：0)
好的，我的理论如下。来自copyNextSampleBuffer的CVPixelBufferRef已经与GPU上的IOSurface相关联。
我能够通过获取CVPixelBufferRef数据并使用它创建一个传递给[CIImage imageWithCGImage：]的CGImageRef来完成这项工作。
实现如下（类方法，放在任何类中）。
+(CGImageRef) imageWithCVPixelBuffer:(CVPixelBufferRef)pixelBuffer
{
CGImageRef image = NULL;
CGColorSpaceRef colorSpace = (CGColorSpaceRef)CVBufferGetAttachment((CVImageBufferRef)pixelBuffer,kCVImageBufferCGColorSpaceKey,NULL);
if (REQUIRED_DEBUG(colorSpace!=NULL))
{
image = [self imageWithCVPixelBuffer:pixelBuffer colorSpace:colorSpace];
}
return image;
}
+(CGImageRef) imageWithCVPixelBuffer:(CVPixelBufferRef)pixelBuffer colorSpace:(CGColorSpaceRef)colorSpace
{
return [self imageWithCVPixelBuffer:pixelBuffer colorSpace:colorSpace copyMemory:YES];
}
static void sReleaseCVPixelBuffer(void* pixelBuffer, const void *data=0, size_t size=0)
{
if (REQUIRED_DEBUG(pixelBuffer!=NULL))
{
REQUIRED_CVRETURN(CVPixelBufferUnlockBaseAddress((CVPixelBufferRef)pixelBuffer,kCVPixelBufferLock_ReadOnly));
CVPixelBufferRelease((CVPixelBufferRef)pixelBuffer);
}
}
static void sReleasePixelMemory(void* pixel_memory, const void *data=0, size_t size=0)
{
if (REQUIRED_DEBUG(pixel_memory!=NULL))
free(pixel_memory);
}
+(CGImageRef) imageWithCVPixelBuffer:(CVPixelBufferRef)pixelBuffer colorSpace:(CGColorSpaceRef)colorSpace copyMemory:(BOOL)copyMemory
{
CGImageRef imageRef = NULL;
CGBitmapInfo imageBitmapInfo = 0;
OSType sourcePixelFormat = CVPixelBufferGetPixelFormatType(pixelBuffer);
if ( kCVPixelFormatType_32ARGB==sourcePixelFormat )
imageBitmapInfo = kCGBitmapByteOrder32Big|kCGImageAlphaNoneSkipFirst;
else if ( kCVPixelFormatType_32BGRA == sourcePixelFormat )
imageBitmapInfo = kCGBitmapByteOrder32Little|kCGImageAlphaNoneSkipFirst;
if (REQUIRED_DEBUG(imageBitmapInfo!=0) && REQUIRED_DEBUG(colorSpace!=NULL))
{
size_t imageRowBytes = CVPixelBufferGetBytesPerRow(pixelBuffer);
size_t imageWidth = CVPixelBufferGetWidth(pixelBuffer);
size_t imageHeight = CVPixelBufferGetHeight(pixelBuffer);
if (REQUIRED_CVRETURN(CVPixelBufferLockBaseAddress( pixelBuffer, kCVPixelBufferLock_ReadOnly )))
{
size_t imageDataSizeBytes = imageRowBytes*imageHeight;
void* imageBaseAddress = CVPixelBufferGetBaseAddress(pixelBuffer);
if (REQUIRED_DEBUG(imageBaseAddress!=NULL))
{
if (copyMemory)
{
void* pixel_memory = malloc(imageDataSizeBytes);
if (REQUIRED_DEBUG(pixel_memory!=NULL))
{
memcpy(pixel_memory,imageBaseAddress,imageDataSizeBytes);
CGDataProviderRef imageDataProvider = CGDataProviderCreateWithData(pixel_memory, pixel_memory, imageDataSizeBytes, sReleasePixelMemory);
if (REQUIRED_DEBUG(imageDataProvider!=NULL))
{
imageRef = CGImageCreate(imageWidth, imageHeight, 8, 32, imageRowBytes, colorSpace, imageBitmapInfo, imageDataProvider, NULL, true, kCGRenderingIntentDefault);
CGDataProviderRelease(imageDataProvider);
}
}
}
else /* make an alias of the bits in the CVPixelBuffer */
{
CGDataProviderRef imageDataProvider = CGDataProviderCreateWithData((void*)pixelBuffer, imageBaseAddress, imageDataSizeBytes, sReleaseCVPixelBuffer);
if (REQUIRED_DEBUG(imageDataProvider!=NULL))
{
CVPixelBufferRetain(pixelBuffer);
imageRef = CGImageCreate(imageWidth, imageHeight, 8, 32, imageRowBytes, colorSpace, imageBitmapInfo, imageDataProvider, NULL, true, kCGRenderingIntentDefault);
REQUIRED_DEBUG(imageRef!=NULL);
CGDataProviderRelease(imageDataProvider);
}
else
sReleaseCVPixelBuffer(pixelBuffer);
}
}
}
}
REQUIRED_DEBUG(imageRef!=NULL);
return imageRef;
}
+(CIImage*) coreImageForPixelBuffer:(CVPixelBufferRef)pixelBuffer colorSpace:(CGColorSpaceRef)colorSpace
{
CIImage* coreImage = nil;
#if 0 // FAILS TARGET_OS_IPHONE
REQUIRED_DEBUG(coreImage = [CIImage imageWithCVPixelBuffer:pixelBuffer]);
#else
CGImageRef pixelBufferImageRef = [self imageWithCVPixelBuffer:pixelBuffer colorSpace:colorSpace];
if (REQUIRED_DEBUG(pixelBufferImageRef!=NULL))
{
REQUIRED_DEBUG(coreImage=[CIImage imageWithCGImage:pixelBufferImageRef]);
CGImageRelease(pixelBufferImageRef);
}
#endif
return coreImage;
}