如何从静止图像（png）渲染固定长度的视频文件

Question

我正在尝试从静止图像（png）创建指定长度的视频。我的代码基于How do I export UIImage as a movie

中给出的答案

我的代码创建了正确长度的视频，但是图像直到最后一帧才出现。我希望在视频的整个过程中显示图像。 （这些视频将在无间隔的时间轴中占位。）

我的代码是：

- (NSURL*)exportImage:(NSImage*)image asMovieLength:(double)seconds {

    NSURL *outFile;
    AppDelegate *theApp;
    NSError *error=nil;
    AVAssetWriter *videoWriter;
    NSDictionary *videoSettings;
    AVAssetWriterInput* writerInput;
    CVPixelBufferRef buffer = NULL;
    AVAssetWriterInputPixelBufferAdaptor *adaptor;

    theApp = (AppDelegate*)[[NSApplication sharedApplication] delegate];

    outFile = [theApp getFilenameForFillerFile];

    videoWriter = [[AVAssetWriter alloc] initWithURL:outFile fileType:AVFileTypeMPEG4 error:&error];
    NSParameterAssert(videoWriter);

    videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:AVVideoCodecH264, AVVideoCodecKey,
                     [NSNumber numberWithInt:880], AVVideoWidthKey,
                     [NSNumber numberWithInt:880], AVVideoHeightKey,
                     nil];

    writerInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];

    adaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput
                                                                               sourcePixelBufferAttributes:nil];

    NSParameterAssert(writerInput);
    NSParameterAssert([videoWriter canAddInput:writerInput]);
    [videoWriter addInput:writerInput];

    // Start the writing session
    [videoWriter startWriting];
    [videoWriter startSessionAtSourceTime:kCMTimeZero];


    if(writerInput.readyForMoreMediaData)
    {
        CMTime zeroTime = CMTimeMake(0, 600);
        CMTime frameTime = CMTimeMake(seconds*600, 600);
        buffer = [self pixelBufferFromImage:image];

        [adaptor appendPixelBuffer:buffer withPresentationTime:frameTime];

        [writerInput markAsFinished];

        [videoWriter finishWritingWithCompletionHandler:^{
            NSLog(@"Finished writing...checking completion status...");
            if (videoWriter.status != AVAssetWriterStatusFailed && videoWriter.status == AVAssetWriterStatusCompleted)
            {
                NSLog(@"Video writing succeeded.");

            } else
            {
                NSLog(@"Video writing failed: %@", videoWriter.error);
            }

        }];

        CVPixelBufferPoolRelease(adaptor.pixelBufferPool);

        NSLog (@"Done");
    }

    return outFile;
}

如何使图像从头开始显示并持续指定的时间？

Answer 1

在您的代码中进行更改之后，对我来说很成功。

CMTime zeroTime = CMTimeMake(0, 600);
CMTime frameTime = CMTimeMake((seconds * 0.5) * 600, 600);

buffer = [self pixelBufferFromImage:image];

[adaptor appendPixelBuffer:buffer withPresentationTime:zeroTime];
[adaptor appendPixelBuffer:buffer withPresentationTime:frameTime];