iOS：音频单位：设置任意采样率
我可以设置任何我想要的采样率吗？有什么限制？
硬件采样率怎么样？一旦设置完毕，对单元之间传递的内部采样率有何限制？
我猜测实际的硬件速率可能必须是 44.1KHz 的一些位移，并且任何内部采样率必须是该原始值的向下位移（例如 22.1KHz、11.05KHz）。这很接近吗？
据我了解，
1. 我设置音频会话的硬件采样率。
2.系统将设置采样率尽可能接近我指定的采样率。
3. 然后，我在音频会话中查询我设置的相同属性，这将为我提供它正在使用的实际采样率
在音频单元（特别是 RemoteIO 单元）级别，文档指出该单元连接到的两个点硬件（即麦克风（输入）总线的输入范围和扬声器（输出）总线的输出范围），采样率可能检索但是 >未设置。
但是，我在构造远程 I/O 单元时尝试访问该值，结果返回零。我想也许我需要启动该单元，然后才能从其连接中获取有意义的数据（启动它的行为可能会创建连接）。因此，这里的解决方案似乎是从音频会话中获取采样率并使用它，如上所述。
需要标签：音频单元
Can I set any sample rate I want? What are the restrictions?
How about the hardware sample rate? And once that is set, what is the restriction on the internal sample rates passed between units?
I'm guessing that the actual hardware rate may have to be some bit shift of 44.1KHz, and any internal sample rates must be a downward bit shift of this original value (e.g. 22.1KHz, 11.05KHz). Is this close?
As far as I understand,
1. I set the hardware sample rate from the Audio Session.
2. The system will set a sample rate as close as it is able to the sample rate I specified.
3. I then query the audio session for the same property I set, which will give me the actual sample rate it is using
At the level of audio units, specifically the RemoteIO unit, documentation states that the two points at which the unit connects to the hardware (ie the input scope of the microphone (input) bus and the output scope of the speaker (output) bus), the sample rate may be retrieved but not set.
However, I attempt to access this value while constructing the remote I/O unit, and it returns zero. I guess maybe I need to start the unit before I can get meaningful data from its connections (the act of starting it probably creates the connections). So the solution here appears to be to get the sample rate from the audio session and use that, as per the above.
NEED TAG: Audio-Unit
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自从你提到 AudioSessions 以来，我假设你使用的是 iOS。因此您需要：
检查音频输入硬件。
AudioSessionGetProperty (kAudioSessionProperty_AudioInputAvailable...)将音频会话设置为“播放和录制”模式。
AudioSessionSetProperty (kAudioSessionProperty_AudioCategory...)和kAudioSessionCategory_PlayAndRecord激活会话。
AudioSessionSetActive()获取首选采样率。
AudioSessionGetProperty (kAudioSessionProperty_CurrentHardwareSampleRate)然后，您可以使用正确的采样率设置音频处理链。
至于播放音频，您可以使用任何采样率，API 应将其转换为硬件的输出采样率。显然，如果您使用非常高的采样率，则会消耗大量内存和 CPU 时间。
I'm assuming you're on iOS since you mention AudioSessions. So you'll want to:
Check for audio input hardware.
AudioSessionGetProperty (kAudioSessionProperty_AudioInputAvailable...)Set audio session to "play & record" mode.
AudioSessionSetProperty (kAudioSessionProperty_AudioCategory...)withkAudioSessionCategory_PlayAndRecordActivate the session.
AudioSessionSetActive()Get the preferred sample rate.
AudioSessionGetProperty (kAudioSessionProperty_CurrentHardwareSampleRate)Then you can set up your audio processing chain with the correct sample rate.
As for playing back audio, you can use any sample rate and the API should convert it to the hardware's output sample rate. Obviously if you use a very high sample rate, it'l consume a lot of memory and CPU time.