extAudioFile 数据...我得到了正确的东西吗？
我正在使用 Core Audio SDK 文档中提供的 EXTAudioFileReadTest 应用程序，并且尝试从 mData 缓冲区获取所有浮点值，以便我可以用它们绘制波形。
目前，我正在打印单通道的浮点值，这就是我在控制台中得到的内容：
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] 0.127136
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] -0.057033
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] -0.146455
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] 0.090759
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] 0.240837
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] -0.072719
2010-09-10 19:22:43.361 ExtAudioFileReadTest[71828:a0f] -0.258782
2010-09-10 19:22:43.361 ExtAudioFileReadTest[71828:a0f] -0.063972
2010-09-10 19:22:43.361 ExtAudioFileReadTest[71828:a0f] 0.088692
2010-09-10 19:22:43.361 ExtAudioFileReadTest[71828:a0f] 0.153571
2010-09-10 19:22:43.361 ExtAudioFileReadTest[71828:a0f] 0.080644
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] -0.087060
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] 0.196455
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] 0.167777
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] -0.192430
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] -0.209936
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] 0.012049
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] 0.110493
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] 0.150715
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] 0.016413
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] -0.056843
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] 0.206117
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] 0.020673
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] -0.561129
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] -0.184265
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] 0.620910
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] 0.309018
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] -0.371634
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] -0.238362
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] 0.125136
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] 0.139757
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] -0.023419
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] -0.142903
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] 0.041068
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] 0.252621
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] -0.002240
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] -0.261686
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] -0.105053
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] 0.072798
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] 0.141572
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] 0.110190
我想我很困惑..因为我期望找到某种类型的电压样本而不是-1和1之间的数字。这些值的实际含义是什么？将这些值转换为 0 到 1 之间的某个上限/下限的好公式是什么？
提前致谢。我一直在到处搜索，但在任何地方都找不到此信息......尤其是在文档中。
I am using the EXTAudioFileReadTest app provided in the Core Audio SDK documentation and I'm trying to get all of the floating point values from the mData buffer so that I can draw a waveform with them.
Currently, I'm printing out the floating point values for single channel and this is what I'm getting in the console:
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] 0.127136
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] -0.057033
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] -0.146455
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] 0.090759
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] 0.240837
2010-09-10 19:22:43.360 ExtAudioFileReadTest[71828:a0f] -0.072719
2010-09-10 19:22:43.361 ExtAudioFileReadTest[71828:a0f] -0.258782
2010-09-10 19:22:43.361 ExtAudioFileReadTest[71828:a0f] -0.063972
2010-09-10 19:22:43.361 ExtAudioFileReadTest[71828:a0f] 0.088692
2010-09-10 19:22:43.361 ExtAudioFileReadTest[71828:a0f] 0.153571
2010-09-10 19:22:43.361 ExtAudioFileReadTest[71828:a0f] 0.080644
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] -0.087060
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] 0.196455
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] 0.167777
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] -0.192430
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] -0.209936
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] 0.012049
2010-09-10 19:22:43.383 ExtAudioFileReadTest[71828:a0f] 0.110493
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] 0.150715
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] 0.016413
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] -0.056843
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] 0.206117
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] 0.020673
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] -0.561129
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] -0.184265
2010-09-10 19:22:43.384 ExtAudioFileReadTest[71828:a0f] 0.620910
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] 0.309018
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] -0.371634
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] -0.238362
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] 0.125136
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] 0.139757
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] -0.023419
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] -0.142903
2010-09-10 19:22:43.385 ExtAudioFileReadTest[71828:a0f] 0.041068
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] 0.252621
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] -0.002240
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] -0.261686
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] -0.105053
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] 0.072798
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] 0.141572
2010-09-10 19:22:43.386 ExtAudioFileReadTest[71828:a0f] 0.110190
I guess i'm confused.. .as I was expecting to find some type of voltage sample and not a number between -1 and 1. What do these values actually mean? What would be a good formula for converting these values to some upper/lower limit that would be between 0 and 1?
Thanks in advance. I've been searching all over the place and can't find this information anywhere... especially not in the documentation.
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这是正常的。
音频样本的通用浮点表示从 [-1...1] 调制；其中值 -1 和 1 代表 0 dBFS 处的一个样本。
浮点值“0.0”的连续流表示无声信号。
没有直流偏移的信号在正域和负域具有相同的权重。
如果您想将这些值转换为 [0...1]，请使用以下公式：
但如果信号超出 [-1...1]，您可能必须使用更复杂的算法。
在大多数情况下，如果您想将其存储为浮点型，则应将其保留为 [-1...1]。
this is normal.
the common floating point representation of audio samples modulate from [-1...1]; where the values -1 and 1 represent one sample at 0 dBFS.
a continuous stream of floating point values '0.0' represents a silent signal.
a signal with no DC offset will have equal weight in the positive and negative domains.
if you'd like to convert these values to [0...1], use the formula:
but you may have to use a more sophisticated algorithm if the signal extends beyond [-1...1].
in most cases, you should keep it at [-1...1] if you want to store it in floating point.
我想我已经弄清楚了。我刚刚在 Excel 中绘制了上面的这些点，它看起来像一个波形。我没有意识到它也会给出负电压......但这是有道理的。
I think i've figured this out. I just graphed those points above in excel and it seems to look like a waveform. I didn't realize it was giving the negative voltages as well... but it makes sense.