c - 由电影支持的 QTMovie 最初可以工作，但不能以其他方法工作

Question

接下来是一个初始化方法。它从文件创建电影结构，着眼于提取原始像素进行处理，如 Apple QA1443 所示。 。然后将其包装在 QTMovie 中 – sourceMovie = [QTMovie movieWithQuickTimeMovie: ...] – 为了方便起见。

初始化这样一个对象后，调用第二个方法，我们尝试使用sourceMovie。然而，事实证明，任何尝试访问这里的 sourceMovie 都会导致 EXC_BAD_ACCESS 例如，NSLog(@"%@", sourceMovie) 是不可能的。这部电影似乎已被取消分配，但原因尚不清楚。

此外，在第二种方法中，获取 CVPixelBufferRef 的常用方法无法正常运行:QTVisualContextIsNewImageAvailable 似乎总是返回 NO，而 QTVisualContextCopyImageForTime 总是为您提供指向 0x00 的 imageBuffer。 (我想如果 QTMovie、Movie 或 VisualContext 以某种方式被释放，这并不奇怪。)

接下来的问题是，为什么第二种方法无法访问 sourceMovie ？它是否像看起来那样被取消分配？如果是这样，为什么？

现在是代码，对于长度，提前表示歉意。

// From the .h, we have the following inst var declarations:
Movie                    myMovie;
QTMovie                  *sourceMovie;
QTVisualContextRef        visualContext;
CVPixelBufferRef         imageBuffer;
pixels_xy                sourceSize;
MovieAnalyzer            *analyzer;

// And now to the @implementation...

-(id)initWithFileString:(NSString *)file {
    if (self = [super init]) {
        NSError *e;

        // Bit of a hack - get the movie size using temporary QTMovie.
        sourceMovie = [QTMovie movieWithFile:file error:&e];
        if (e) {
            [self release];
            NSLog(@"Could not open movie.");
            return nil;
        }

        NSSize movieSize = [[sourceMovie posterImage] size];
        CGRect bounds = CGRectMake(0, 0, movieSize.width, movieSize.height);

        // Save the size in pixels.
        sourceSize.x = (int)movieSize.width, sourceSize.y = (int)movieSize.height;

        CFStringRef movieLocation = (CFStringRef) file;

        // Get a QT Visual Context, and create a movie inialized to use it for output.
        visualContext = NULL;
        OSStatus status = CreatePixelBufferContext(k32ARGBPixelFormat, &bounds, &visualContext);
        if (noErr != status && NULL == visualContext) {
            [self release];
            NSLog(@"Problem initializing QT Visual Context.");
            return nil;
        }

        /*** Instantiate the Movie ***/
        myMovie = NULL;
        Boolean trueValue = true;
        QTNewMoviePropertyElement newMovieProperties[3] = {0};

        // Setup movie location
        newMovieProperties[0].propClass = kQTPropertyClass_DataLocation;
        newMovieProperties[0].propID = kQTDataLocationPropertyID_CFStringPosixPath;
        newMovieProperties[0].propValueSize = sizeof(CFStringRef);
        newMovieProperties[0].propValueAddress = &movieLocation;

        // Assign the visual context - could also be NULL
        newMovieProperties[1].propClass = kQTPropertyClass_Context;
        newMovieProperties[1].propID = kQTContextPropertyID_VisualContext;
        newMovieProperties[1].propValueSize = sizeof(visualContext);
        newMovieProperties[1].propValueAddress = &visualContext;

        // Make the movie active
        newMovieProperties[2].propClass = kQTPropertyClass_NewMovieProperty;
        newMovieProperties[2].propID = kQTNewMoviePropertyID_Active;
        newMovieProperties[2].propValueSize = sizeof(trueValue);
        newMovieProperties[2].propValueAddress = &trueValue;

        status = NewMovieFromProperties(3, newMovieProperties, 0, NULL, &myMovie);
        if (status != noErr || myMovie == NULL) {
            NSLog(@"Problem initializing theMovie"); // problem
            [self release];
            return nil;
        }

        // Create a new QTMovie with the Movie as its backing object
        sourceMovie = [QTMovie movieWithQuickTimeMovie:myMovie disposeWhenDone:NO error:&e];
        if (e) {
            NSLog(@"Could not initialize QTMovie from Movie.");
            [self release];
            return nil;
        }

        [sourceMovie stepForward];
        analyzer = [[MovieAnalyzer alloc] initWithColorString:"BGRA" andSourceSize:sourceSize];
    }
    return self;
}


-(NSImage*) supplyCalibrationImage {
    NSLog(@"%x", &sourceMovie);

    [sourceMovie stepForward];    // This fails!
    ....
}

Answer 1

[QTMovie movieWithQuickTimeMovie:disposeWhenDone:error:] 正在返回自动发布的影片。如果您希望它在该方法之后继续存在，则需要保留它。