ios - AVAssetWriter 仅在 iOS 13 设备上具有音频“噼啪声”

Question

我使用 AVCaptureSession 使用 AVAssetWriter 写入 mov 文件。iOS 13 之前的设备上的相同代码没有裂纹。在所有 iOS 13 设备上，无论 iPhone/iPad 型号如何，都有音频噼啪声。

我已将此作为错误提交给 Apple，但我担心我遗漏了一些简单的东西。还有其他人遇到这种情况吗？我可以更改设置的任何想法吗？

我尝试过的事情

1. 改变 mov -> mpeg
2. 尝试了多种音频编解码器（尤其是 AppleLossless 和 AAC）
3. 推送到主队列而不是指定的 captureQueue
4. 试过 AVCaptureMovieFileOutput，crackle 不存在。问题特定于 AVAssetWriter
5. AVCaptureSession 总是在 44100 中提供音频，所以我在 AVAssetWriter 中将其重新采样为 48000。裂纹仍然存在。

任何想法都会有所帮助！

设置

 self.session = [[AVCaptureSession alloc] init];
[self.session setSessionPreset:AVCaptureSessionPresetiFrame1280x720];

NSError *error;
AVCaptureDevice *inputVideoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
AVCaptureDeviceInput *deviceVideoInput = [AVCaptureDeviceInput deviceInputWithDevice:inputVideoDevice error:&error];
if ([self.session canAddInput:deviceVideoInput]) {
    [self.session addInput:deviceVideoInput];
}

AVCaptureDevice* mic = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
AVCaptureDeviceInput* micinput = [AVCaptureDeviceInput deviceInputWithDevice:mic error:nil];
if ([self.session canAddInput:micinput]) {
    [self.session addInput:micinput];
}

AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
output.videoSettings = @{ (NSString *)kCVPixelBufferPixelFormatTypeKey:@(kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange) };
[output setSampleBufferDelegate:self queue:_captureQueue];
[self.session addOutput:output];

AVCaptureAudioDataOutput* audioout = [[AVCaptureAudioDataOutput alloc] init];
[audioout setSampleBufferDelegate:self queue:_captureQueue];
[self.session addOutput:audioout];

[self setCameraPosition:NO];

[self.session startRunning];

self.preview = [AVCaptureVideoPreviewLayer layerWithSession:_session];
self.preview.videoGravity = AVLayerVideoGravityResizeAspect;

AVAssetWriter 初始化

 _path = path;
    [[NSFileManager defaultManager] removeItemAtPath:_path error:nil];
    NSURL *url = [NSURL fileURLWithPath:self.path];
    _writer = [AVAssetWriter assetWriterWithURL:url fileType:AVFileTypeQuickTimeMovie error:nil];
    NSDictionary* settings = [NSDictionary dictionaryWithObjectsAndKeys:
                              AVVideoCodecH264, AVVideoCodecKey,
                              [NSNumber numberWithFloat: frameSize.width], AVVideoWidthKey,
                              [NSNumber numberWithFloat: frameSize.height], AVVideoHeightKey,
                              nil];
    _videoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:settings];
    _videoInput.expectsMediaDataInRealTime = YES;
    [_writer addInput:_videoInput];

    AudioChannelLayout acl;
    bzero( &acl, sizeof(acl));
    acl.mChannelLayoutTag = kAudioChannelLayoutTag_Mono;
    settings = [NSDictionary dictionaryWithObjectsAndKeys:
                [ NSNumber numberWithInt: kAudioFormatMPEG4AAC], AVFormatIDKey,
                [ NSNumber numberWithInt:(int)channels], AVNumberOfChannelsKey,
                [ NSNumber numberWithFloat:sampleRate], AVSampleRateKey,
                [ NSNumber numberWithInt: 64000 ], AVEncoderBitRateKey,
                nil];

    _audioInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:settings];
    _audioInput.expectsMediaDataInRealTime = YES;
    [_writer addInput:_audioInput];

    [_writer startWriting];

更新:: iPhone 11+ 设备没有噼啪声，似乎他们在引擎盖下使用编解码器进行了更改，导致“旧”设备出现问题。我已向 Apple 提交了一个错误并使用了技术支持。技术支持已验证 iPhone 11 没问题，而任何旧设备都有问题。对错误票的响应为零。

如果你能在可预见的未来远离 AVAssetWriter。

标签： iosobjective-cavcapturesessionavassetwriter