Question

我正在使用带有单个视频输入的AVAssetWriter将视频帧写入电影。写循环的机制不是问题：但我发现内存管理是。

关于CMSampleBufferRef我将附加： a）我为一些图像数据（原始字节）创建一个CVPixelBufferRef。因此CVPBR拥有数据。 b）然后我将其包装在CMSampleBufferRef中，如此（为简洁起见，删除了错误检查）：

    + (CMSampleBufferRef)wrapImageBufferInCMSampleBuffer:(CVImageBufferRef)imageBuffer timingInfo:(CMSampleTimingInfo const *)timingInfo error:(NSError **)error {
    // Create a format description for the pixel buffer
        CMVideoFormatDescriptionRef formatDescription = 0;
        OSStatus result = CMVideoFormatDescriptionCreateForImageBuffer(kCFAllocatorDefault, imageBuffer, &formatDescription);

        // Finally, create a CMSampleBuffer wrapper around it all
        CMSampleBufferRef sampleBuffer = nil;
        OSStatus sampleBufferResult = CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault, imageBuffer, YES, nil, nil, formatDescription, timingInfo, &sampleBuffer);

        if (formatDescription) {
            CFRelease(formatDescription);
        }

        return sampleBuffer;
    }

这为我创建了一个可以传递给AVWriter的缓冲区。到现在为止还挺好。问题是，如果我在将缓冲区附加到编写器之后释放缓冲区，我会看到奇怪的扭曲。

如果我这样做：

    [avInput appendSampleBuffer:delayedBuffer]
    CFRelease(sampleBuffer);
    CFRelease(pixelBuffer);

然后它工作，没有内存泄漏，但偶尔I will see corrupted frames。注意有时不同步的帧，以及第391,394帧的明显内存损坏。对我来说，在AVF完成编码之前，内存缓冲区似乎已被释放。

如果我删除CFRelease（pixelBuffer），问题就会消失。 resulting movie is perfectly smooth完全没有腐败。当然;那我有一个多GB内存泄漏的问题！

有没有其他人遇到这样的事情？

btw：如果我使用AVAssetWriterInputPixelBufferAdaptor也没关系。获得了相同的结果。

以下是重现问题的完整代码段：

- (void)recordMovieUsingStandardAVFTo:(NSURL *)url colorSequence:(NSArray *)colorSequence frameDuration:(CMTime)frameDuration size:(NSSize)size {
    NSError *error = nil;
    AVAssetWriter *writer = [AVAssetWriter assetWriterWithURL:url fileType:AVFileTypeQuickTimeMovie error:&error];
    if ([self checkForError:error doing:@"creation of asset writer"] == NO) {
        return;
    }

    NSMutableDictionary *videoSettings = [NSMutableDictionary dictionary];
    [videoSettings setValue:[NSNumber numberWithLong:(long) size.width] forKey:AVVideoWidthKey];
    [videoSettings setValue:[NSNumber numberWithLong:(long) size.height] forKey:AVVideoHeightKey];
    [videoSettings setValue:AVVideoCodecH264 forKey:AVVideoCodecKey];

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

    [writer addInput:videoInput];
    [writer startWriting];
    [writer startSessionAtSourceTime:kCMTimeZero];

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_async(queue, ^{
        NSError *localError = nil;
        CMTime frameTime = kCMTimeZero;
        int frameCounter = 0;
        for (int i = 0; i < 4; i++) {
            @autoreleasepool {
                for (NSColor *color in colorSequence) {
                    CMSampleTimingInfo timing = kCMTimingInfoInvalid;
                    timing.presentationTimeStamp = frameTime;
                    timing.duration = frameDuration;

                    while (videoInput.isReadyForMoreMediaData == NO) {
                        [NSThread sleepForTimeInterval:0.1];
                    }

                    CVPixelBufferRef pixelBuffer = [self createPixelBufferBufferOfColor:color size:size];
                    CMSampleBufferRef sampleBuffer = [OSGUtils wrapImageBufferInCMSampleBuffer:pixelBuffer timingInfo:&timing error:&localError];

                    BOOL recordingSuccess = [videoInput appendSampleBuffer:sampleBuffer];
                    if (recordingSuccess) {
                        frameTime = CMTimeAdd(frameTime, frameDuration);
                        frameCounter++;
                        if (frameCounter % 60 == 0) {
                            ApplicationLogInfo(@"Wrote frame at time %@", [NSString niceStringForCMTime:frameTime]);
                        }
                    } else {
                        ApplicationLogError(@"Can't write frame at time %@", localError);
                    }

                    CFRelease(sampleBuffer);
                    CFRelease(pixelBuffer);
                }
            }
        }

        [videoInput markAsFinished];
        [writer endSessionAtSourceTime:frameTime];
        BOOL success = [writer finishWriting];
        if (!success) {
            ApplicationLogError(@"Failed to finish writing, %@, %d", writer.error, writer.status);
        } else {
            ApplicationLogInfo(@"Write complete");
        }
    });
}

使用AVAssetWriter时PixelBuffer未被释放

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