了解网络音频中的getByteTimeDomainData和getByteFrequencyData [英] understanding getByteTimeDomainData and getByteFrequencyData in web audio
问题描述
无论我在哪里，这两种方法的文档都非常通用。我想知道我正在查看我从每个方法得到的返回数组到底是什么。
The documentation for both of these methods are both very generic wherever I look. I would like to know what exactly I'm looking at with the returned arrays I'm getting from each method.
对于getByteTimeDomainData，每次传递涵盖的时间段？我相信大多数的oscopes每次传球覆盖32毫秒的跨度。这也包括在内吗？对于实际的元素值本身，范围似乎是0 - 255.这相当于-1 - +1伏？
For getByteTimeDomainData, what time period is covered with each pass? I believe most oscopes cover a 32 millisecond span for each pass. Is that what is covered here as well? For the actual element values themselves, the range seems to be 0 - 255. Is this equivalent to -1 - +1 volts?
对于getByteFrequencyData，所涵盖的频率基于采样率，所以每个指标都是一个实际频率，但实际的元素值本身呢？是否有一个dB范围等于返回数组中返回的值？
For getByteFrequencyData the frequencies covered is based on the sampling rate, so each index is an actual frequency, but what about the actual element values themselves? Is there a dB range that is equivalent to the values returned in the returned array?
推荐答案
getByteTimeDomainData （以及较新的 getFloatTimeDomainData ）返回您请求的大小数组 - 其 frequencyBinCount ，计算为所请求的 fftSize 的一半。当然，该数组是在 AudioContext 上公开的当前 sampleRate ，所以如果它是默认的2048 fftSize ， frequencyBinCount 将为1024，如果您的设备以44.1kHz运行，则相当于大约23ms的数据。
getByteTimeDomainData (and the newer getFloatTimeDomainData) return an array of the size you requested - its frequencyBinCount, which is calculated as half of the requested fftSize. That array is, of course, at the current sampleRate exposed on the AudioContext, so if it's the default 2048 fftSize, frequencyBinCount will be 1024, and if your device is running at 44.1kHz, that will equate to around 23ms of data.
字节值的范围介于0-255之间，是的，映射到-1到+1，因此128为零。 （它不是伏特，而是全范围无单位值。）
The byte values do range between 0-255, and yes, that maps to -1 to +1, so 128 is zero. (It's not volts, but full-range unitless values.)
如果你使用 getFloatFrequencyData ，返回的值是以dB为单位;如果您使用 Byte 版本，则会根据 minDecibels / maxDecibels 映射值（参见 minDecibels / maxDecibels 描述）。
If you use getFloatFrequencyData, the values returned are in dB; if you use the Byte version, the values are mapped based on minDecibels/maxDecibels (see the minDecibels/maxDecibels description).
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