fmod：如何使用FMOD_OUTPUTTYPE_WAVWRITER_NRT？
这是我之前的问题的后续： 渲染一些声音数据到一个新的声音数据中？
我正在创建一个程序，该程序将处理一个包含声音库和时间偏移的文件，以标记何时必须播放声音并从中生成波形文件。
所以我认为 FMOD_OUTPUTTYPE_WAVWRITER 非常适合这项工作。
对于声音库，想象一下文件中的类似内容：
0 kick.wav
1 hit.wav
2 flute.wav
左侧的数字描述右侧声音文件名的声音 ID， 时间偏移量：
1000 0
2000 1
3000 2
左边的数字告诉程序何时必须以毫秒为单位播放声音，右边的数字是声音 ID。
因此，当我启动程序时，FMOD将生成一个波形文件，其中第一秒包含踢脚（来自kick.wav），第二秒包含打击，第三秒包含长笛，我将不得不等待至少 3 秒才能完成任务。
但是，如果我想渲染更长的音乐，比如 5 分钟，那么我必须等待至少 5 分钟才能完成任务，因为我让它依赖于系统计时器以指定的偏移量播放声音在文件中和 while(true) 循环来更新 FMOD::System。我认为必须有一种方法可以更快地渲染，而无需等待程序在指定时间实际渲染声音，因为我在 DAW 程序中看到，例如索尼 ACID，可以非常快地渲染曲目。
然后我看了一下API参考，有FMOD_OUTPUTTYPE_WAVWRITER_NRT，然后我想这可能是解决方案，所以我尝试立即更改输出设备而不修改其他任何内容，生成的波形文件听起来很混乱！我听到很多重复的声音，长时间的延迟等等。
那么，如何正确使用非实时版本呢？在我的情况下使用 NRT 时更新 fmod 系统的正确方法是什么？
我在 fmod 文档本身中找不到有关 NRT 输出类型使用的明确解释。
无论如何，我在Windows环境下使用C++。
谢谢。
this is a follow up to my earlier question: Rendering some sound data into one new sound data?
I'm creating a program that will process a file containing a sound bank and time offsets to mark when the sound must be played and generate a wave file from it.
So I suppose FMOD_OUTPUTTYPE_WAVWRITER is perfect for the job.
For the sound bank, imagine something like this in a file:
0 kick.wav
1 hit.wav
2 flute.wav
where the number on the left describes the sound ID of the sound file name on the right,
and the time offsets:
1000 0
2000 1
3000 2
where the number on the left tells the program when the sound must be played in milliseconds, and number on the right is the sound ID.
Therefore, when I start the program, FMOD will generate a wave file which contains a kick (from kick.wav) in the first second, a hit in the second second, and a flute in the third second, and I will have to wait for at least 3 seconds for the task to complete.
However, if I want to render a longer music, say, 5 minutes, then I must have to wait for at least 5 minutes for the task to complete, since I make it depend on the system timer to play the sound at the specified offset in the file and a while(true) loop to update FMOD::System. I think there must be a way to render faster without waiting for the program to actually render the sound at the specified time, since I saw in a DAW program like, say, Sony ACID, can render the tracks really fast.
Then I take a bit look into the API reference, there's FMOD_OUTPUTTYPE_WAVWRITER_NRT, then I thought this maybe the solution, so I tried changing the output device right away without modifying anything else, and the generated wave file sounds messed up! I hear many repetitive sound, long delays, etc.
So, how to use the non-realtime version properly? What is the correct way to update the fmod system when using NRT in my case?
I couldn't find a clear explanation about the usage of NRT ouput type in the fmod documentation itself.
Anyway, I use C++ in a Windows environment.
Thanks.
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FMOD_OUTPUTTYPE_WAVEWRITER_NRT 的工作方式是每次调用 System::update 时都会生成音频。每次“更新”生成的数据量由 System::setDSPBufferSize 的 bufferlength 参数控制。
因此，调用 System::update 的速度越快，生成数据的速度就越快。现在，您工作的重要部分是将“x”次对 System::update 的调用转换为可以与您的时间线匹配的内容。
默认情况下，FMOD 的运行采样率为每秒 48000 个样本（可通过 System::setSoftwareFormat 配置）。因此，如果将 'bufferlength' 设置为 1024，则每次调用 System::update 都会生成 1024 个样本（写入 wav 文件）。所以...
1024 / 48000 = 0.021333 秒 ~ 21.3 毫秒每次调用生成数据。现在您可以计算需要调用 System::update 多少次才能获得您拥有的时间戳。
The way FMOD_OUTPUTTYPE_WAVEWRITER_NRT works is it generates audio every time System::update is called. The amount of data generated per 'update' is governed by the bufferlength parameter of System::setDSPBufferSize.
So the faster you call System::update the faster the data is generated. Now the important part for your job is to convert 'x' number of calls to System::update into something you can match to your timeline.
By default FMOD operates at a sample rate of 48000 samples per second (configurable via System::setSoftwareFormat). So if you set 'bufferlength' to 1024, each time you call System::update 1024 samples will be generated (written to the wav file). So...
1024 / 48000 = 0.021333 seconds ~ 21.3 milliseconds of data is generated per call. Now you can calculate how many times you need to call System::update to get to the timestamps you have.