appendSampleBuffer与音频AVAssetWriterInput"泄漏"内存,直到endSessionAtSourceTime

Question

我有一个奇怪的记忆"泄漏" AVAssetWriterInput appendSampleBuffer.我正在同时写视频和音频,所以我有一个AVAssetWriter有两个输入,一个用于视频,一个用于音频:

self.videoWriter = [[[AVAssetWriter alloc] initWithURL:[self.currentVideo currentVideoClipLocalURL]
                                              fileType:AVFileTypeMPEG4
                                                 error:&error] autorelease];
...
self.videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo
                                                           outputSettings:videoSettings];
self.videoWriterInput.expectsMediaDataInRealTime = YES;
[self.videoWriter addInput:self.videoWriterInput];
...
self.audioWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio
                                                           outputSettings:audioSettings];
self.audioWriterInput.expectsMediaDataInRealTime = YES;
[self.videoWriter addInput:self.audioWriterInput];

我开始写作,表面上的一切都很好.视频和音频被写入并对齐等等.但是,我将我的代码放入分配工具并注意到以下内容:

音频字节将保留在内存中,我将在一秒钟内证明.这是内存中的增长.音频字节仅在我调用后才会释放[self.videoWriter endSessionAtSourceTime:...],您会看到内存使用量急剧下降.这是我的音频编写代码,它作为一个块被分派到一个串行队列:

@autoreleasepool
{
    // The objects that will hold the audio data
    CMSampleBufferRef sampleBuffer;
    CMBlockBufferRef  blockBuffer1;
    CMBlockBufferRef  blockBuffer2;

    size_t nbytes = numSamples * asbd_.mBytesPerPacket;

    OSStatus status = noErr;
    status = CMBlockBufferCreateWithMemoryBlock(kCFAllocatorDefault,
                                                data,
                                                nbytes,
                                                kCFAllocatorNull,
                                                NULL,
                                                0,
                                                nbytes,
                                                kCMBlockBufferAssureMemoryNowFlag,
                                                &blockBuffer1);

    if (status != noErr)
    {
        NLog(@"CMBlockBufferCreateWithMemoryBlock error at buffer 1");
        return;
    }

    status = CMBlockBufferCreateContiguous(kCFAllocatorDefault,
                                           blockBuffer1,
                                           kCFAllocatorDefault,
                                           NULL,
                                           0,
                                           nbytes,
                                           kCMBlockBufferAssureMemoryNowFlag | kCMBlockBufferAlwaysCopyDataFlag,
                                           &blockBuffer2);

    if (status != noErr)
    {
        NSLog(@"CMBlockBufferCreateWithMemoryBlock error at buffer 2");
        CFRelease(blockBuffer1);
        return;
    }

    // Finally, create the CMSampleBufferRef
    status = CMAudioSampleBufferCreateWithPacketDescriptions(kCFAllocatorDefault,
                                                             blockBuffer2,
                                                             YES,   // Yes data is ready
                                                             NULL,  // No callback needed to make data ready
                                                             NULL,
                                                             audioFormatDescription_,
                                                             1,
                                                             timestamp,
                                                             NULL,
                                                             &sampleBuffer);


    if (status != noErr)
    {
        NSLog(@"CMAudioSampleBufferCreateWithPacketDescriptions error.");
        CFRelease(blockBuffer1);
        CFRelease(blockBuffer2);
        return;
    }

    if ([self.audioWriterInput isReadyForMoreMediaData])
    {
        if (![self.audioWriterInput appendSampleBuffer:sampleBuffer])
        {
            NSLog(@"Couldn't append audio sample buffer: %d", numAudioCallbacks_);
        }
    } else {
        NSLog(@"AudioWriterInput isn't ready for more data.");
    }

    // One release per create
    CFRelease(blockBuffer1);
    CFRelease(blockBuffer2);
    CFRelease(sampleBuffer);
}

如您所见,我每次创建时都会释放一次缓冲区.我已将"泄漏"追溯到附加音频缓冲区的行:

[self.audioWriterInput appendSampleBuffer:sampleBuffer]

我通过评论该行证明了这一点,之后我获得了以下"无泄漏"分配图(尽管现在录制的视频现在没有音频):

我尝试了另外一件事,即添加回来appendSamplebuffer然后双重释放blockBuffer2:

CFRelease(blockBuffer1);
CFRelease(blockBuffer2);
CFRelease(blockBuffer2); // Double release to test the hypothesis that appendSamplebuffer is retaining this
CFRelease(sampleBuffer);

这样做不会导致双重释放,表明该blockBuffer2点的保留计数为2.这产生了相同的"无泄漏"分配图,除了当我打电话时[self.videoWriter endSessionAtSourceTime:...],我从一个双重崩溃release(表示self.videoWriter正在尝试释放所有blockBuffer2已传入的s的指针).

如果相反,我尝试以下方法:

CFRelease(blockBuffer1);
CFRelease(blockBuffer2);
CMSampleBufferInvalidate(sampleBuffer); // Invalidate sample buffer
CFRelease(sampleBuffer);

然后[self.audioWriterInput appendSampleBuffer:sampleBuffer] ,在此之后的每次通话中,附加视频帧的调用开始失败.

所以我的结论是,AVAssetWriter或者AVAssetWriterInput一直保留blockBuffer2到视频完成录制.显然,如果视频录制的时间足够长,这可能会导致实际的内存问题.难道我做错了什么？

编辑:我得到的音频字节是PCM格式,而我正在写的视频格式是MPEG4,该视频的音频格式是MPEG4AAC.视频编写器是否可能在运行中执行PCM - > AAC格式,这就是为什么它会被缓冲？

Answer 1

既然您已经等待了一个月的答案，我会给您一个不太理想但可行的答案。

您可以使用 ExtendedAudioFile 函数编写单独的文件。然后您可以将视频和音频与 AVComposition 一起播放。我认为如果您需要在录制结束时将它们合成，您也许可以使用 AVFoundation 将咖啡馆和视频合成在一起，而无需重新编码。

这将使您开始运行，然后您可以在闲暇时解决内存泄漏问题。