我正在使用类似于audioTap example from apple的audioTapProcessor .
基本上,audioTapProcessor 被创建并添加到audioMix 中:
MTAudioProcessingTapRef audioProcessingTap;
if (noErr == MTAudioProcessingTapCreate(kCFAllocatorDefault, &callbacks, kMTAudioProcessingTapCreationFlag_PreEffects, &audioProcessingTap))
{
audioMixInputParameters.audioTapProcessor = audioProcessingTap;
CFRelease(audioProcessingTap);
audioMix.inputParameters = @[audioMixInputParameters];
_audioMix = audioMix;
}
当创建audioMix时,它被添加到avPlayer的currentItem中:
self.avPlayer.currentItem.audioMix = audioMix;
当我完成audioTapProcessor 后,我会清除对audioTapProcessor 和audioMix 的引用:
if (self.avPlayer.currentItem.audioMix){
for (AVMutableAudioMixInputParameters *inputParameter in player.currentItem.audioMix.inputParameters) {
inputParameter.audioTapProcessor = nil;
}
player.currentItem.audioMix = nil;
}
这会触发tap_UnprepareCallback和tap_FinalizeCallback函数,并且audioTapProcessor对象被释放。
在 iOS11 几天前发布之前,这一切都没有任何问题。
在 iOS11 设备上,我有时会在 ClientProcessingTapManager 线程上收到 EXC_BAD_ACCESS 错误。错误发生在AVFoundation的其中一个类中,所以我无法调试。该错误发生在 ClientProcessingTap::PerformTap 中的某处。
我已向audioTap 回调添加了日志记录,看起来只有tap_ProcessCallBack 在ClientProcessingTapManager 线程上执行。
我认为有时audioTapProcessor的tap_ProcessCallback方法会在此线程上触发,而实际的audioTapProcessor已在另一个线程上释放。
我的问题是:如何正确停止 audioTapProcessor 并将其从内存中删除?
这是一些输出日志记录示例:
2017-09-22 12:49:26:171 xx[1261:780894] cleaning up audioMix of AvPlayer
2017-09-22 12:49:26:213 xx[1261:781173] into tap_ProcessCallback. thread: ClientProcessingTapManager
2017-09-22 12:49:26:213 xx[1261:781173] end of tap_ProcessCallback
2017-09-22 12:49:26:217 xx[1261:781127] into tap_UnprepareCallback.
2017-09-22 12:49:26:218 xx[1261:781127] end of tap_UnprepareCallback
2017-09-22 12:49:26:218 xx[1261:781127] into tap_FinalizeCallback.
2017-09-22 12:49:26:218 Tunify[1261:781127] end of tap_FinalizeCallback
2017-09-22 12:49:26:218 Tunify[1261:781127] into MYAudioTapProcessor dealloc.
(lldb)
很高兴知道:
我正在使用 avPlayers 池,因此我正在重用这些对象。当我不清除 avPlayers 的 audioMix 时,我不会遇到此错误。如果不清理 audioMix 对象,只有当我重用 avPlayer 并将新的 audioMix 分配给 avPlayer 时,audioTapProcessors 才会被释放。
我找到了related question ,但我已经触发了清理功能。那里的解决方案在 iOS11 设备上给出了相同的错误
最佳答案
这是 iOS 11 下 AVFoundation 的一个错误。已在 iOS 12 中修复。 针对该问题的雷达rdar://34977000
一个可能的解决方法是在释放 AVPlayer/AVPlayerItem 之前调用prepareReleaseAudioMix:
+ (void)prepareReleaseAudioMix:(AVAudioMix*)audioMix {
if ( @available(iOS 11.0, *) ) {
// Starting with iOS 11, it is not required to manually nil audioTapProcessor,
// but we need to retain the audioMix for a bit to make sure the processing callback
// will not be called after we release (this is due to a bug in iOS 11 which calls the release
// callback but still calls the processing callback afterwards - it also releases internal data
// on release, so simply checking for release in the processing block is not enough)
// rdar://34977000
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[self _prepareReleaseAudioMixNow:audioMix];
});
} else {
// Prior to iOS 11 we need to manually nil the audioTapProcessor
[self _prepareReleaseAudioMixNow:audioMix];
}
}
+ (void)_prepareReleaseAudioMixNow:(AVAudioMix*)audioMix {
for ( AVMutableAudioMixInputParameters *parameters in audioMix.inputParameters ) {
if ( ![parameters isKindOfClass:[AVMutableAudioMixInputParameters class]] )
continue;
parameters.audioTapProcessor = nil;
}
}
关于ios - 如何在 iOS 11 中正确停止和删除音频处理器,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/46362859/