AVFoundation 视频导出 - 无故出错 [Objective-C]

Question

我正在尝试使用 AVFoundation 为视频颜色应用程序编码视频（您可以查看 here）。导出编解码器将是 H264 或 ProRes 或 HEVC（取决于用户选择），如果这有助于解决我的问题。

我已经根据答案编写了我的代码：Make movie file with picture Array and song file, using AVAsset

还有来自 github 的代码：https://github.com/caferrara/img-to-video/blob/master/img-to-video/ViewController.m#L29

这是我得到的（有一些外部变量和函数调用，但我认为很清楚发生了什么）：

NSURL * outURL = [NSURL fileURLWithPath:[NSString stringWithFormat: @"%s", path]];

NSLog(outURL.absoluteString);

NSError * error = nil;
AVAssetWriter * videoWriter = [[AVAssetWriter alloc] initWithURL: outURL
                              fileType:AVFileTypeQuickTimeMovie
                                                          error:&error];

NSDictionary * videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               encoder->codec, AVVideoCodecKey,
                               [NSNumber numberWithInt:encoder->width], AVVideoWidthKey,
                               [NSNumber numberWithInt:encoder->height], AVVideoHeightKey,
                               nil ];

AVAssetWriterInput * videoWriterInput = [AVAssetWriterInput
                                        assetWriterInputWithMediaType:AVMediaTypeVideo
                                        outputSettings:videoSettings];


AVAssetWriterInputPixelBufferAdaptor * adaptor = [AVAssetWriterInputPixelBufferAdaptor
                                                 assetWriterInputPixelBufferAdaptorWithAssetWriterInput:videoWriterInput
                                                 sourcePixelBufferAttributes:nil];

videoWriterInput.expectsMediaDataInRealTime = YES;
[videoWriter addInput:videoWriterInput];

//Start a session:
[videoWriter startWriting];
NSLog(@"Write Started");
[videoWriter startSessionAtSourceTime:kCMTimeZero];


//Video encoding

CVPixelBufferRef buffer = NULL;

setMlvAlwaysUseAmaze(App->videoMLV);

for(uint64_t f = 0; f < getMlvFrames(App->videoMLV); ++f)
{
    getMlvProcessedFrame16(App->videoMLV, f, encoder->data);
    CVReturn success = CVPixelBufferCreateWithBytes( kCFAllocatorDefault,
                                                     encoder->width,
                                                     encoder->height,
                                                     kCVPixelFormatType_48RGB,
                                                     encoder->data,
                                                     sizeof(uint16_t) * encoder->width * 3,
                                                     NULL,
                                                     NULL,
                                                     NULL,
                                                     &buffer );
    if (success != kCVReturnSuccess || buffer == NULL) NSLog(@"Failed to create pixel buffer.");
    NSDictionary * colour_attachment = @{(id)kCVImageBufferICCProfileKey : (id)encoder->colour_profile_data};
    CVBufferSetAttachments(buffer, (CFDictionaryRef)colour_attachment, kCVAttachmentMode_ShouldPropagate);

    BOOL append_ok = NO;
    int j = 0;
    while (!append_ok && j < 30) {
        if (adaptor.assetWriterInput.readyForMoreMediaData)  {
            //print out status:
            NSLog(@"Processing video frame (%d, attempt %d)", (int)f, j);

            CMTime frameTime = CMTimeMake(f * 5000.0, (int32_t)(encoder->fps * 1000.0));
            append_ok = [adaptor appendPixelBuffer:buffer withPresentationTime:frameTime];
            if(!append_ok){
                NSError *error = videoWriter.error;
                if(error!=nil) {
                    NSLog(@"Unresolved error %@,%@.", error, [error userInfo]);
                }
            }
            while(!adaptor.assetWriterInput.readyForMoreMediaData) [NSThread sleepForTimeInterval:0.0001];
        }
        else {
            printf("adaptor not ready %d, %d\n", (int)f, j);
            while(!adaptor.assetWriterInput.readyForMoreMediaData) [NSThread sleepForTimeInterval:0.0001];
        }
        j++;
    }
    if (!append_ok) {
        printf("error appending image %d times %d\n, with error.", (int)f, j);
    }
}

[videoWriterInput markAsFinished];
[videoWriter finishWriting];

[videoWriterInput release];
[videoWriter release];

NSLog(@"Write Ended");

但是，每当我尝试运行它时，它都会打印以下错误：

2017-11-15 20:54:40.532 MLV App[21801:3488295] Unresolved error Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo={NSLocalizedFailureReason=An unknown error occurred (-12905), NSLocalizedDescription=The operation could not be completed, NSUnderlyingError=0x7fd446adeb70 {Error Domain=NSOSStatusErrorDomain Code=-12905 "(null)"}},{
NSLocalizedDescription = "The operation could not be completed";
NSLocalizedFailureReason = "An unknown error occurred (-12905)";
NSUnderlyingError = "Error Domain=NSOSStatusErrorDomain Code=-12905 \"(null)\""; }.

我在互联网上四处寻找这个错误代码的含义，但那是无用的。

我在这里使用 AVFoundation 有什么大问题吗？ 我也试过切换到 8 位 RGB 帧，没有解决问题。

Answer 1

并非所有列出的像素格式都得到框架的实际支持。不支持您选择的那个。坚持使用 kCVPixelFormatType_32ARGB、kCVPixelFormatType_422YpCbCr8 等标准格式。

kVTPixelTransferNotSupportedErr = -12905 通过https://www.osstatus.com/

关于 Core Video 支持的像素格式的技术问答： https://developer.apple.com/library/content/qa/qa1501/_index.html

请注意，您可能希望运行代码以查找给定操作系统版本上支持的格式的最新列表。此外，并非每个框架中的每个路径都支持每种格式。换句话说，进行像素格式之间转换的 VideoToolbox 可能不支持格式 X，即使您可以创建该格式的 CVPixelBuffer。

在您的情况下，请尝试 kCVPixelFormatType_4444AYpCbCr16、kCVPixelFormatType_422YpCbCr16、kCVPixelFormatType_422YpCbCr10 或 kCVPixelFormatType_64ARGB，因为它们至少在解码端受支持： https://developer.apple.com/documentation/avfoundation/avassetreadertrackoutput