为什么我的AudioQueueOutputCallback不能被调用？ [英] Why might my AudioQueueOutputCallback not be called?

问题描述

我正在使用音频队列服务API ，用于通过iPhone上的TCP套接字连接播放从服务器流式传输的音频。我可以播放从套接字连接填充的缓冲区，我似乎无法让我的AudioQueue调用我的AudioQueueOutputCallback函数，而且我没有想法。

I'm using the Audio Queue Services API to play audio streamed from a server over a TCP socket connection on an iPhone. I can play the buffers that were filled from the socket connection, I just cannot seem to make my AudioQueue call my AudioQueueOutputCallback function, and I'm out of ideas.

1. 数据从套接字连接传递给播放器，并立即将
   写入内存中的循环缓冲区。


2. 当AudioQueueBuffers变为可用时，数据将从循环缓冲区复制到
   可用的AudioQueueBuffer中，并立即重新排队。 （或者，如果我的回调发生了）

会发生什么

缓冲区都已成功填充和排队，我清楚地听到了音频流。为了测试，我使用大量的缓冲区（15）并且所有缓冲区都无缝地播放，但是AudioQueueOutputCallback永远不会被调用，因此我从不重新排队任何缓冲区，尽管事实上一切似乎都在完美地运行。如果我不等待我的回调，假设它永远不会被调用，而是根据写入的数据驱动缓冲区的入队，我可以无限期地播放音频流，重用和重新入队缓冲区，就好像它们一样已经通过回调明确地回复了我。事实就是这样：我可以根据需要重复使用缓冲区来完美地播放流，这让我感到困惑。为什么不调用回调？

What happens

The buffers are all filled and enqueued successfully, and I hear the audio stream clearly. For testing, I use a large number of buffers (15) and all of them play through seamlessly, but the AudioQueueOutputCallback is never called, so I never re-queue any of those buffers, despite the fact that everything seems to be working perfectly. If I don't wait for my callback, assuming it will never be called, and instead drive the enqueueing of buffers based on the data as it is written, I can play the audio stream indefinitely, reusing and re-enqueueing buffers as if they had been explicitly returned to me by the callback. It is that fact: that I can play the stream perfectly while reusing buffers as needed, that confuses me the most. Why isn't the callback being called?

流的格式是16位线性PCM，8 kHz，单声道：

The format of the stream is 16 bit linear PCM, 8 kHz, Mono:

_streamDescription.mSampleRate = 8000.0f;
_streamDescription.mFormatID = kAudioFormatLinearPCM;
_streamDescription.mBytesPerPacket = 2;
_streamDescription.mFramesPerPacket = 1;
_streamDescription.mBytesPerFrame = sizeof(AudioSampleType);
_streamDescription.mChannelsPerFrame = 1;
_streamDescription.mBitsPerChannel = 8 * sizeof(AudioSampleType)
_streamDescription.mReserved = 0;
_streamDescription.mFormatFlags = (kLinearPCMFormatFlagIsBigEndian | 
                                   kLinearPCMFormatFlagIsPacked);

我的原型和回调实现如下。没有什么花哨的，与我到目前为止看到的每个例子几乎相同：

My prototype and implementation of the callback are as follows. Nothing fancy, and pretty much identical to every example I've seen so far:

// Prototype, declared above the class's @implementation
void AQBufferCallback(void* inUserData, AudioQueueRef inAudioQueue, AudioQueueBufferRef inAudioQueueBuffer);

// Definition at the bottom of the file.
void AQBufferCallback(void* inUserData, AudioQueueRef inAudioQueue, AudioQueueBufferRef inAudioQueueBuffer) {

    printf("callback\n");
    [(MyAudioPlayer *)inUserData audioQueue:inAudioQueue didAquireBufferForReuse:inAudioQueueBuffer];
}

我像这样创建AudioQueue：

I create the AudioQueue like this:

OSStatus status = 0;
status = AudioQueueNewOutput(&_streamDescription, 
                             AQBufferCallback, // <-- Doesn't work...
                             self, 
                             CFRunLoopGetCurrent(),
                             kCFRunLoopCommonModes, 
                             0,
                             &_audioQueue);
if (status) {

    // This is not called...
    NSLog(@"Error creating new audio output queue: %@", [MyAudioPlayer stringForOSStatus:status]);
    return;
}

我将这样的缓冲区排入队列。此时，已知本地缓冲区包含用于复制的正确数据量：

And I enqueue buffers like this. At this point, it is known that the local buffer contains the correct amount of data for copying:

memcpy(aqBuffer->mAudioData, localBuffer, kAQBufferSize);
aqBuffer->mAudioDataByteSize = kAQBufferSize;

OSStatus status = AudioQueueEnqueueBuffer(_audioQueue, aqBuffer, 0, NULL);
if (status) {
    // This is also not called.
    NSLog(@"Error enqueueing buffer %@", [MyAudioPlayer stringForOSStatus:status]);
}

请救我。

推荐答案

这是在主线程还是后台线程上执行的？如果 CFRunLoopGetCurrent（）返回可能消失的线程的运行循环（线程池等），或者是一个不关心<$ c $的运行循环，可能不太好c> kCFRunLoopCommonModes 。

Is this executed on the main thread or a background thread? probably not good if CFRunLoopGetCurrent() returns a run loop of a thread that could disappear (thread pool etc) or is a run loop that don't care about kCFRunLoopCommonModes.

尝试将 CFRunLoopGetCurrent（）更改为 CFRunLoopGetMain（）或确保执行 AudioQueueNewOutput（）和执行CFRunLoopGetCurrent（）在主线程或您可以控制的线程上，并且具有正确的运行循环。

Try to change CFRunLoopGetCurrent() to CFRunLoopGetMain() or make sure AudioQueueNewOutput() and CFRunLoopGetCurrent() is executed on the main thread or a thread that you have control over and has a proper run loop.

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