CODEWITHSUNDEEP
androidaudio-recordingaudiorecord
paviflo
paviflo

Reputation: 125

Meaning of values from Audiorecord.read()

I am trying to understand what do the values obtained with Audiorecord.read() actually mean.

I am trying to create an app that will start recording sound when it will detect an impulse reponse (therefore I have though to set a treshold in which any sound above it will be considered an impulse).

The problem is that I don´t really know what do the values stored in "data" represent when I call this method:

read = recorder.read(data, 0, bufferSize);

These are some of the values that I obtain:

[96, 2, 101, 3, 101, 2, 110, 1, -41, 2, -80, 2, -117, 2, 119, 2, -94, 0 .........]

The idea is to set the treshold from these values but firstly I need to know what do they represent.

Can you guys help me with this?

Upvotes: 5

Views: 4434

Answers (1)

Gabe Sechan
Gabe Sechan

Reputation: 93559

The data depends on the parameters you sent to the constructor. AudioRecord (int audioSource, int sampleRateInHz, int channelConfig, int audioFormat, int bufferSizeInBytes)

sampleRateInHz is the number of samples per second. channel config is either MONO or STEREO meaning 1 or 2 channels. format is PCM8 or PCM16 meaning 8 bits or 16 bits per sample.

So the data is an array of samples. Each sample is an array of channels. Each channel is going to have an 8 or 16 bit value, depending on what you asked for. No data will be skipped, it will always be a fixed size format.

So if you chose 1 channel and 8 bits, each byte is a single sound heard, and you should see sampleRateInHz sounds per second. If you choose 16 bits, each sound is 2 bytes long. If you use 2 channels, it should go in order channel 1 then channel 2 for each sample.

The individual values are the amplitude of the sound data when sampled at the requested frequency. See http://en.wikipedia.org/wiki/Pulse-code_modulation for more information on how it works.

Upvotes: 6

Related Questions