Audio filter that changes track volume #193
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| // replace sample at index with volume adjusted value | ||
| buffer.put( | ||
| index, | ||
| (buffer.get(index) * (BASE.pow(volume) -1 ) / (BASE - 1)).toInt().toShort() |
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Is this based on a common gain calculation? Hope it won't create unexpected noise/distortion.
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Yes. Audio volume is exponential, so I took an exponential formula from here: https://stackoverflow.com/questions/1165026/what-algorithms-could-i-use-for-audio-volume-level which seems to work well.
Distortion can happen, I don't think there is a way to prevent that. Furthermore, sometimes it can be done on purpose.
| * - value <1 will lower the volume | ||
| * - value >1 will increase it. One has to be careful with these, since large values may result in distortion. | ||
| */ | ||
| class VolumeFilter(@FloatRange(from = 0.0) private val volume: Double) : BufferFilter{ |
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Filter doesn't seem associated with audio processing (thinking about sound effect, boost, mixer, etc). Possible better naming?
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I couldn't really come up with better common naming for audio and video frame modifications. I guess "filter" works better with video because it became a common term with video/photo filters in popular apps. With audio "filters" have more of a "signal processing" meaning low/high pass filter, etc. Maybe we can keep "filter" terminology within LiTr?
Our first audio filter. Simplest one, changes track volume: