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使用 Mac OSX Objective-C，我正在尝试创建一个命令行工具，该工具将单个 H.264 和单个 AAC 文件作为输入 - 从相同的源材料编码 - 并使用 AVAssetWriter 创建单个 QuickTime 兼容mov (和/或 m4v) 文件以供进一步编辑/分发。

到目前为止我所做的： 1) 使用 AVFoundation 框架组件，即 AVAssetWriter、AVAssetWriterInput 等和核心媒体框架组件，即 CMSampleBufferCreate、CMBlockBufferReplaceDataBytes 等 - 我已经对 CL 工具进行了原型设计。2) 我已经连接了输入/输出文件的 URL，创建了 AVAssetWriter 和 AVAssetWriterInput、CMBlockBuffer 等。 3) 当我执行我的 runLoop 时，AVAssetWriter 创建了 m4v 文件，但是，虽然它格式正确，但它是只有一个 136 字节的文件，表示没有视频轨道数据的电影头原子。4) 我搜索了 StackOverflow - 以及 Apple 论坛和互联网 - 以找到我的特定问题的答案。

使用我的代码中的错误检查以及 Xcode 调试器，我发现 AVAssetWriter 设置正确 - 它开始构建电影文件 - 但 CMBlockBufferReplaceDataBytes 不会将 H.264 NAL 数据写入 CMBlockBuffer（我相信我应该做）。那么我错过了什么？

这是我的 runLoop 代码的相关部分：

// Create the videoFile.m4v AVAssetWriter.
AVAssetWriter *videoFileWriter = [[AVAssetWriter alloc] initWithURL:destinationURL fileType:AVFileTypeQuickTimeMovie error:&error];
NSParameterAssert(videoFileWriter);
if (error) {
    NSLog(@"AVAssetWriter initWithURL failed with error= %@", [error localizedDescription]);
}

// Create the video file settings dictionary.
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys: AVVideoCodecH264, AVVideoCodecKey, [NSNumber numberWithInt:1280],
                               AVVideoWidthKey, [NSNumber numberWithInt:720], AVVideoHeightKey, nil];

// Perform video settings check.
if ([videoFileWriter canApplyOutputSettings:videoSettings forMediaType:AVMediaTypeVideo]) {
    NSLog(@"videoFileWriter can apply videoSettings...");    
}

// Create the input to the videoFileWriter AVAssetWriter.
AVAssetWriterInput *videoFileWriterInput = [[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];
videoFileWriterInput.expectsMediaDataInRealTime = YES;
NSParameterAssert(videoFileWriterInput);
NSParameterAssert([videoFileWriter canAddInput:videoFileWriterInput]);

// Connect the videoFileWriterInput to the videoFileWriter.
if ([videoFileWriter canAddInput:videoFileWriterInput]) {
   [videoFileWriter addInput:videoFileWriterInput]; 
}

// Get the contents of videoFile.264 (using current Mac OSX methods).
NSData *sourceData = [NSData dataWithContentsOfURL:sourceURL];
const char *videoFileData = [sourceData bytes];
size_t sourceDataLength = [sourceData length];
NSLog(@"The value of 'sourceDataLength' is: %ld", sourceDataLength);

// Set up to create the videoSampleBuffer.
int32_t videoWidth = 1280;
int32_t videoHeight = 720;
CMBlockBufferRef videoBlockBuffer = NULL;
CMFormatDescriptionRef videoFormat = NULL;
CMSampleBufferRef videoSampleBuffer = NULL;
CMItemCount numberOfSampleTimeEntries = 1;
CMItemCount numberOfSamples = 1;

// More set up to create the videoSampleBuffer.
CMVideoFormatDescriptionCreate(kCFAllocatorDefault, kCMVideoCodecType_H264, videoWidth, videoHeight, NULL, &videoFormat);
result = CMBlockBufferCreateWithMemoryBlock(kCFAllocatorDefault, NULL, 150000, kCFAllocatorDefault, NULL, 0, 150000, kCMBlockBufferAssureMemoryNowFlag,
                                            &videoBlockBuffer);
NSLog(@"After 'CMBlockBufferCreateWithMemoryBlock', 'result' is: %d", result);

// The CMBlockBufferReplaceDataBytes method is supposed to write videoFile.264 data bytes into the videoSampleBuffer.
result = CMBlockBufferReplaceDataBytes(videoFileData, videoBlockBuffer, 0, 150000);
NSLog(@"After 'CMBlockBufferReplaceDataBytes', 'result' is: %d", result);

CMSampleTimingInfo videoSampleTimingInformation = {CMTimeMake(1, 30)};
result = CMSampleBufferCreate(kCFAllocatorDefault, videoBlockBuffer, TRUE, NULL, NULL, videoFormat, numberOfSamples, numberOfSampleTimeEntries,
                              &videoSampleTimingInformation, 0, NULL, &videoSampleBuffer);
NSLog(@"After 'CMSampleBufferCreate', 'result' is: %d", result);

// Set the videoSampleBuffer to ready (is this needed?).
result = CMSampleBufferMakeDataReady(videoSampleBuffer);
NSLog(@"After 'CMSampleBufferMakeDataReady', 'result' is: %d", result);

// Start writing...
if ([videoFileWriter startWriting]) {
    [videoFileWriter startSessionAtSourceTime:kCMTimeZero];
}

// Start the first while loop (DEBUG)...

欢迎所有想法、意见和建议。

谢谢！

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1 回答 1

0

问题在于 CMSampleBufferCreate 您传入零 numSampleSizeEntries 和 NULL sampleSizeArray。如果你什么都不传入，那么什么都不会被写入！

于 2012-09-12T10:40:41.700 回答