iphone - AVASSETWriterInput 用于从 Iphone 问题上的图像制作视频

Question

我尝试了以下两种将 UIImage 的像素缓冲区附加到 ASSETWriterInput 的方法。一切看起来都很好，除了视频文件中没有数据。怎么了？

1 适配器类

AVAssetWriterInputPixelBufferAdaptor * avAdaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput sourcePixelBufferAttributes:NULL];

[avAdaptor appendPixelBufferixelBuffer withPresentationTime:CMTimeMake(1, 10)];

2 制作

// Create sample buffer.
CMSampleBufferRef sampleBuffer = NULL;
result = CMSampleBufferCreateForImageBuffer(kCFAllocatorDef ault, pixelBuffer, true, NULL, NULL, videoInfo, &timing, &sampleBuffer);

// Ship out the frame.
NSParameterAssert(CMSampleBufferDataIsReady(sample Buffer));
NSParameterAssert([writerInput isReadyForMoreMediaData]);
BOOL success = [writerInput appendSampleBuffer:sampleBuffer];

Answer 1

我发现出于某种原因我需要多次追加缓冲区。这个例子中我制作的测试应用程序的时间可能不合适，但既然它有效，它应该给你一个好主意。

+ (void)writeImageAsMovie:(UIImage*)image toPath:(NSString*)path size:(CGSize)size duration:(int)duration 
{
    NSError *error = nil;
    AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:
                                  [NSURL fileURLWithPath:path] fileType:AVFileTypeQuickTimeMovie
                                                              error:&error];
    NSParameterAssert(videoWriter);

    NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                   AVVideoCodecH264, AVVideoCodecKey,
                                   [NSNumber numberWithInt:size.width], AVVideoWidthKey,
                                   [NSNumber numberWithInt:size.height], AVVideoHeightKey,
                                   nil];
    AVAssetWriterInput* writerInput = [[AVAssetWriterInput
                                        assetWriterInputWithMediaType:AVMediaTypeVideo
                                        outputSettings:videoSettings] retain];

    AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor
                                                     assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput
                                                     sourcePixelBufferAttributes:nil];
    NSParameterAssert(writerInput);
    NSParameterAssert([videoWriter canAddInput:writerInput]);
    [videoWriter addInput:writerInput];

    //Start a session:
    [videoWriter startWriting];
    [videoWriter startSessionAtSourceTime:kCMTimeZero];

    //Write samples:
    CVPixelBufferRef buffer = [Utils pixelBufferFromCGImage:image.CGImage size:size];
    [adaptor appendPixelBuffer:buffer withPresentationTime:kCMTimeZero];
    [adaptor appendPixelBuffer:buffer withPresentationTime:CMTimeMake(duration-1, 2)];

    //Finish the session:
    [writerInput markAsFinished];
    [videoWriter endSessionAtSourceTime:CMTimeMake(duration, 2)];
    [videoWriter finishWriting];
}

此方法不是必需的，但在这里用作像素缓冲区源的示例:

+ (CVPixelBufferRef) pixelBufferFromCGImage:(CGImageRef)image size:(CGSize)size
{
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey,
                             [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey,
                             nil];
    CVPixelBufferRef pxbuffer = NULL;
    CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, size.width,
                          size.height, kCVPixelFormatType_32ARGB, (CFDictionaryRef) options, 
                          &pxbuffer);
    status=status;//Added to make the stupid compiler not show a stupid warning.
    NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);

    CVPixelBufferLockBaseAddress(pxbuffer, 0);
    void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
    NSParameterAssert(pxdata != NULL);

    CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(pxdata, size.width,
                                                 size.height, 8, 4*size.width, rgbColorSpace, 
                                                 kCGImageAlphaNoneSkipFirst);
    NSParameterAssert(context);

    //CGContextTranslateCTM(context, 0, CGImageGetHeight(image));
    //CGContextScaleCTM(context, 1.0, -1.0);//Flip vertically to account for different origin

    CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image), 
                                         CGImageGetHeight(image)), image);
    CGColorSpaceRelease(rgbColorSpace);
    CGContextRelease(context);

    CVPixelBufferUnlockBaseAddress(pxbuffer, 0);

    return pxbuffer;
}