Analyzers and Visualizers

Overview

All visualizer goes with a pair of nodes Initxxx and Getxxx. Init nodes must be called before of the Get nodes to reserve the buffer analysis data, and after the audio source initialization. During the audio playback, you can use the player controls (Start/Stop/Pause) to interact with the analysis process.

Visualizer nodes flow

Channel Result Object

Channel mode and “by Channel” nodes

To be able to do multiple operations with each channel audio data the Channel Mode has been added to the configuration parameters of our analysis. So now we have 3 options:

All in one: Accumulates all channels data into only one array, to get the analysis result can be used the old Getxxx nodes
Select one: Returns only the channel specified in Channel option. Now to obtain only a Right Channel analysis you must select Channel Mode: Select one and Channel: 1

Split all: Returns each channel analysis into one array. You must use the new Getxxx By Channel nodes to retrieve the results. The output of this nodes are a Channel Result Object Reference. You can access to the number of channels and the data for each channel using the channel number as index.

To interact with the result object we have 2 nodes

Get Num Channels

Returns number of channels stored in the object

**Get Channel Result**
Returns the analysis result of a specific channel. 
Channel	Index of the channel

Run Time Analysis nodes

Amplitude

One of the most basic audio visualizer, just to retrieve the amplitude values of the audio wave.

**Init Amplitude Config**
Configures the wave amplitude analyzer. 
Channel Mode	All in one, Select one, Split all
Channel	Number of channel to be analyzed (Only valid for Select one option)
Num Time Bands	Number of bands to display, it determines the resolution of the wave display
Time Window	Interval Time showed by the display in seconds

Get Amplitude

Returns the amplitude values of the wave

Get Amplitude By Channel

Returns the amplitude values of the wave. The output is a Channel Result Object Reference.

Frequency spectrum

Visualize the frequency spectrum analysis. This analyzer include two frequency data distribution Linear and Logarithmic, but you can define too your own distribution feeding the init node with your own bounds for each band.

**Init Spectrum Config**
Configures the spectrum frequency analyzer. 
Type	Linear, Logarithmic
Channel Mode	All in one, Select one, Split all
Channel	Number of channel to be analyzed (Only valid for Select one option)
Num Freq Bands	Number of bands to distribute the frequencies
Time Window	Time of the frequency sample
History Size	Number of samples used to calculate the average frequencies (Default: 1)
UsePeakValues	Returns peak value of the band instead of average value
Num Peaks	Num of frequency peaks to be calculated by Get Spectrum Peaks

**Init Spectrum Config WLimits**
Configures the spectrum frequency analyzer. The frequency bounds of each band can be defined. 
Channel Mode	All in one, Select one, Split all
Channel	Number of channel to be analyzed (Only valid for Select one option)
Band Limits	TArray of Vector2D to define the bounds of each band, must be sorted and no overlap allowed (Closed Intervals)
Time Window	Time of the frequency sample
History Size	Number of samples used to calculate the average frequencies (Default: 1)
UsePeakValues	Returns peak value of the band instead of average value
Num Peaks	Num of frequency peaks to be calculated by Get Spectrum Peaks

**Get Spectrum**
Returns the frequency spectrum values, and the average values and Calculate Averages Frequencies option is Enabled. 
Calculate Averages Frequencies	Calculates average frequency values too

**Get Spectrum By Channel**
Returns the frequency spectrum values, and the average values and Calculate Averages Frequencies option is Enabled. The output is a Channel Result Object Reference. 
Calculate Averages Frequencies	Calculates average frequency values too

**Get Spectrum Peaks**
Returns the frequency spectrum peaks, retrieve as many peaks as Num Peaks has been set on Init Spectrum Config node, ordered by energy. 
Frequency Peaks	Value in Hz for the frequency peaks
Frequency Peaks Energy	Energy value for the frequency peaks

**Get Spectrum Peaks By Channel**
Returns the frequency spectrum peaks, retrieve as many peaks as Num Peaks has been set on Init Spectrum Config node, ordered by energy. The output is a Channel Result Object Reference. 
Frequency Peaks	Value in Hz for the frequency peaks
Frequency Peaks Energy	Energy value for the frequency peaks

Beat Tracking

This beat tracking analyzer has a basic tracker configuration but you can configure your own tracking bounds too as in the spectrum analyzer. The pre-configured beat tracking use the next frequency limits to track the most valuable ranges of the spectrum.

Bass range: 0 - 87 Hz
Low Mid Range: 500 - 700 Hz
High Mid Range: 5000 - 12000 Hz

BPM Tracking

Now you can obtain the beat-per-minute result of each beat tracking band too.

This analysis returns the partial result of the bpm scan interval configurated and the overall bpm result for the band.

**Init Beat Tracking Config**
Configures the beat tracking visualyzer. 
Channel Mode	All in one, Select one, Split all
Channel	Number of channel to be analyzed (Only valid for Select one option)
Time Window	Time of the frequency sample
History Size	Number of samples used to calculate the average frequencies
Calculate BPM	Enable Beat-per-minute analysis
BPM History Size	Number of beat samples used to calculate the bpm. (Number of calls to GetBeatTracking node)
Threshold	Factor used to trigger the beat, values greater than Threshold * Average trigger this beat

Get Beat Tracking

Returns the basic Beat Tracking results in Bass, Low Mid range and High Mid range, the current band spectrum values, the current BPM counter result for each band and the Total BPM

Get Beat Tracking By Channel

Returns the basic Beat Tracking results in Bass, Low Mid range and High Mid range, the current band spectrum values, the current BPM counter result for each band and the Total BPM. The output is a Channel Result Object Reference.

**Get Beat Tracking WThreshold**
Returns the basic Beat Tracking results in Bass, Low Mid range and High Mid range, and the current band spectrum values, the current BPM counter result for each band and the Total BPM, using the input threshold values. 
Override Threshold	TArray to override the threshold factor for each band

**Get Beat Tracking WThreshold By Channel**
Returns the basic Beat Tracking results in Bass, Low Mid range and High Mid range, and the current band spectrum values, the current BPM counter result for each band and the Total BPM, using the input threshold values. The output is a Channel Result Object Reference. 
Override Threshold	TArray to override the threshold factor for each band

A basic beat tracking over a specific frequency bands, the band bounds can be defined, must be sorted and no overlap allowed (Closed Intervals)

**Init Beat Tracking Config WLimits**
Configures the beat tracking visualyzer 
Channel Mode	All in one, Select one, Split all
Channel	Number of channel to be analyzed (Only valid for Select one option)
Band Limits	TArray of Vector2D to define the bounds of each band, must be sorted and no overlap allowed
Time Window	Time of the frequency sample
History Size	Number of samples used to calculate the average frequencies
Calculate BPM	Enable Beat-per-minute analysis
BPM History Size	Number of beat samples used to calculate the bpm. (Number of calls to GetBeatTracking node)
Threshold	Factor used to trigger the beat, values greater than Threshold * Average trigger this beat

Get Beat Tracking WLimits

Returns the Beat Tracking results for the bands defined in the configuration, the current frequency spectrum values for each band, the current BPM counter result for each band and the Total BPM.

Get Beat Tracking WLimits By Channel

Returns the Beat Tracking results for the bands defined in the configuration, the current frequency spectrum values for each band, the current BPM counter result for each band and the Total BPM. The output is a Channel Result Object Reference.

**Get Beat Tracking WLimits WThreshold**
Returns the basic Beat Tracking results in Bass, Low Mid range and High Mid range, and the current band spectrum values, the current BPM counter result for each band and the Total BPM, using the input threshold values. 
Override Threshold	TArray to override the threshold factor for each band

**Get Beat Tracking WLimits WThreshold By Channel**
Returns the basic Beat Tracking results in Bass, Low Mid range and High Mid range, and the current band spectrum values, the current BPM counter result for each band and the Total BPM, using the input threshold values. The output is a Channel Result Object Reference. 
Override Threshold	TArray to override the threshold factor for each band

Some nodes to return intermediate values

Get Beat Tracking Average

Returns the frequency average values for each band

Get Beat Tracking Average By Channel

Returns the frequency average values for each beat band. The output is a Channel Result Object Reference.

Get Beat Tracking Average and Variance

Returns the frequency average and variance for each beat band

Get Beat Tracking Average and Variance By Channel

Returns the frequency average and variance for each beat band. The output is a Channel Result Object Reference.

Pitch Tracking

Now you can obtain the fundamental frequency of an audio in real-time. It’s an implementation using YIN algorithm.

**Init Pitch Tracking Config**
Configures the pitch tracking analyzer. 
Channel Mode	All in one, Select one, Split all
Channel	Number of channel to be analyzed (Only valid for Select one option)
Time Window	Time of the analysis sample
Threshold	Yin algorithm threshold (Default 0.19)

Get Pitch Tracking

Returns the pitch tracking result, the fundamental frequency value

Get Pitch Tracking By Channel

Returns the pitch tracking result (fundamental frequency value). The output is a Channel Result Object Reference.

Analysis Utils

**Frequency to MIDI**
Converts a frequency value in Hz into MIDI note value. 
Frequency Hz	Frequency value in hertz

**Amplitude to DB**
Converts normalized amplitude values to decibel scale (without device calibration), just calculated as `dB = 20 * log(Amplitude)` 
Amplitude	Amplitude normalized value

Offline Analysis nodes

Amplitude

We need to initialize an Extractor instance to be able to use the offline analysis nodes

**Get Amplitude Section**
Returns the analysis result for a specific section of the audio file. We can set the resolution of the wave. 
Channel Mode	All in one, Select one, Split all
Channel	Number of channel to be analyzed (Only valid for Select one option)
Start Time	Start position of the section (in seconds)
End Time	End position of the section (in seconds)
Resolution	This is the number of samples grouped in each bar. With small values we can obtain more detail of the wave but more results too

**Get Amplitude Section by Channel**
Returns the analysis result for a specific section of the audio file. We can set the resolution of the wave. The output is a Channel Result Object Reference. 
Channel	Number of channel to be analyzed (Only valid for Select one option)
Start Time	Start position of the section (in seconds)
End Time	End position of the section (in seconds)
Resolution	This is the number of samples grouped in each bar. With small values we can obtain more detail of the wave but more results too