# crepePostprocess

## Description

converts the output of a `f0`

= crepePostprocess(`activations`

)`crepe`

pretrained network to pitch estimates in Hz.

specifies the confidence threshold as a nonnegative scalar value less than 1.`f0`

= crepePostprocess(`activations`

,`'ConfidenceThreshold'`

,`TH`

)

For example, ```
f0 =
crepePostprocess(actiations,'ConfidenceThreshold',0.75)
```

specifies a confidence
threshold of 0.75.

## Examples

### Download CREPE Network

Download and unzip the Audio Toolbox™ model for CREPE.

Type `crepe`

at the Command Window. If the Audio Toolbox model for CREPE is not installed, then the function provides a link to the location of the network weights. To download the model, click the link and unzip the file to a location on the MATLAB path.

Alternatively, execute these commands to download and unzip the CREPE model to your temporary directory.

downloadFolder = fullfile(tempdir,'crepeDownload'); loc = websave(downloadFolder,'https://ssd.mathworks.com/supportfiles/audio/crepe.zip'); crepeLocation = tempdir; unzip(loc,crepeLocation) addpath(fullfile(crepeLocation,'crepe'))

Check that the installation is successful by typing `crepe`

at the Command Window. If the network is installed, then the function returns a `DAGNetwork`

(Deep Learning Toolbox) object.

crepe

ans = DAGNetwork with properties: Layers: [34×1 nnet.cnn.layer.Layer] Connections: [33×2 table] InputNames: {'input'} OutputNames: {'pitch'}

### Load Pretrained CREPE Network

Load a pretrained CREPE convolutional neural network and examine the layers and classes.

Use `crepe`

to load the pretrained CREPE network. The output `net`

is a `DAGNetwork`

(Deep Learning Toolbox) object.

net = crepe

net = DAGNetwork with properties: Layers: [34×1 nnet.cnn.layer.Layer] Connections: [33×2 table] InputNames: {'input'} OutputNames: {'pitch'}

View the network architecture using the `Layers`

property. The network has 34 layers. There are 13 layers with learnable weights, of which six are convolutional layers, six are batch normalization layers, and one is a fully connected layer.

net.Layers

ans = 34×1 Layer array with layers: 1 'input' Image Input 1024×1×1 images 2 'conv1' Convolution 1024 512×1×1 convolutions with stride [4 1] and padding 'same' 3 'conv1_relu' ReLU ReLU 4 'conv1-BN' Batch Normalization Batch normalization with 1024 channels 5 'conv1-maxpool' Max Pooling 2×1 max pooling with stride [2 1] and padding [0 0 0 0] 6 'conv1-dropout' Dropout 25% dropout 7 'conv2' Convolution 128 64×1×1024 convolutions with stride [1 1] and padding 'same' 8 'conv2_relu' ReLU ReLU 9 'conv2-BN' Batch Normalization Batch normalization with 128 channels 10 'conv2-maxpool' Max Pooling 2×1 max pooling with stride [2 1] and padding [0 0 0 0] 11 'conv2-dropout' Dropout 25% dropout 12 'conv3' Convolution 128 64×1×128 convolutions with stride [1 1] and padding 'same' 13 'conv3_relu' ReLU ReLU 14 'conv3-BN' Batch Normalization Batch normalization with 128 channels 15 'conv3-maxpool' Max Pooling 2×1 max pooling with stride [2 1] and padding [0 0 0 0] 16 'conv3-dropout' Dropout 25% dropout 17 'conv4' Convolution 128 64×1×128 convolutions with stride [1 1] and padding 'same' 18 'conv4_relu' ReLU ReLU 19 'conv4-BN' Batch Normalization Batch normalization with 128 channels 20 'conv4-maxpool' Max Pooling 2×1 max pooling with stride [2 1] and padding [0 0 0 0] 21 'conv4-dropout' Dropout 25% dropout 22 'conv5' Convolution 256 64×1×128 convolutions with stride [1 1] and padding 'same' 23 'conv5_relu' ReLU ReLU 24 'conv5-BN' Batch Normalization Batch normalization with 256 channels 25 'conv5-maxpool' Max Pooling 2×1 max pooling with stride [2 1] and padding [0 0 0 0] 26 'conv5-dropout' Dropout 25% dropout 27 'conv6' Convolution 512 64×1×256 convolutions with stride [1 1] and padding 'same' 28 'conv6_relu' ReLU ReLU 29 'conv6-BN' Batch Normalization Batch normalization with 512 channels 30 'conv6-maxpool' Max Pooling 2×1 max pooling with stride [2 1] and padding [0 0 0 0] 31 'conv6-dropout' Dropout 25% dropout 32 'classifier' Fully Connected 360 fully connected layer 33 'classifier_sigmoid' Sigmoid sigmoid 34 'pitch' Regression Output mean-squared-error

Use `analyzeNetwork`

(Deep Learning Toolbox) to visually explore the network.

analyzeNetwork(net)

### Estimate Pitch Using CREPE Network

The CREPE network requires you to preprocess your audio signals to generate buffered, overlapped, and normalized audio frames that can be used as input to the network. This example walks through audio preprocessing using `crepePreprocess`

and audio postprocessing with pitch estimation using `crepePostprocess`

. The `pitchnn`

function performs these steps for you.

Read in an audio signal for pitch estimation. Visualize and listen to the audio. There are nine vocal utterances in the audio clip.

[audioIn,fs] = audioread('SingingAMajor-16-mono-18secs.ogg'); soundsc(audioIn,fs) T = 1/fs; t = 0:T:(length(audioIn)*T) - T; plot(t,audioIn); grid on axis tight xlabel('Time (s)') ylabel('Ampltiude') title('Singing in A Major')

Use `crepePreprocess`

to partition the audio into frames of 1024 samples with an 85% overlap between consecutive mel spectrograms. Place the frames along the fourth dimension.

[frames,loc] = crepePreprocess(audioIn,fs);

Create a CREPE network with `ModelCapacity`

set to `tiny`

. If you call `crepe`

before downloading the model, an error is printed to the Command Window with a download link.

netTiny = crepe('ModelCapacity','tiny');

Predict the network activations.

activationsTiny = predict(netTiny,frames);

Use `crepePostprocess`

to produce the fundamental frequency pitch estimation in Hz. Disable confidence thresholding by setting `ConfidenceThreshold`

to `0`

.

`f0Tiny = crepePostprocess(activationsTiny,'ConfidenceThreshold',0);`

Visualize the pitch estimation over time.

plot(loc,f0Tiny) grid on axis tight xlabel('Time (s)') ylabel('Pitch Estimation (Hz)') title('CREPE Network Frequency Estimate - Thresholding Disabled')

With confidence thresholding disabled, `crepePostprocess`

provides a pitch estimate for every frame. Increase the `ConfidenceThreshold`

to `0.8`

.

`f0Tiny = crepePostprocess(activationsTiny,'ConfidenceThreshold',0.8);`

Visualize the pitch estimation over time.

plot(loc,f0Tiny,'LineWidth',3) grid on axis tight xlabel('Time (s)') ylabel('Pitch Estimation (Hz)') title('CREPE Network Frequency Estimate - Thresholding Enabled')

Create a new CREPE network with `ModelCapacity`

set to `full`

.

netFull = crepe('ModelCapacity','full');

Predict the network activations.

```
activationsFull = predict(netFull,frames);
f0Full = crepePostprocess(activationsFull,'ConfidenceThreshold',0.8);
```

Visualize the pitch estimation. There are nine primary pitch estimation groupings, each group corresponding with one of the nine vocal utterances.

plot(loc,f0Full,'LineWidth',3) grid on xlabel('Time (s)') ylabel('Pitch Estimation (Hz)') title('CREPE Network Frequency Estimate - Full')

Find the time elements corresponding to the last vocal utterance.

roundedLocVec = round(loc,2); lastUtteranceBegin = find(roundedLocVec == 16); lastUtteranceEnd = find(roundedLocVec == 18);

For simplicity, take the most frequently occurring pitch estimate within the utterance group as the fundamental frequency estimate for that timespan. Generate a pure tone with a frequency matching the pitch estimate for the last vocal utterance.

lastUtteranceEstimation = mode(f0Full(lastUtteranceBegin:lastUtteranceEnd))

`lastUtteranceEstimation = `*single*
217.2709

The value for `lastUtteranceEstimate`

of `217.3`

Hz. corresponds to the note A3. Overlay the synthesized tone on the last vocal utterance to audibly compare the two.

lastVocalUtterance = audioIn(fs*16:fs*18); newTime = 0:T:2; compareTone = cos(2*pi*lastUtteranceEstimation*newTime).'; soundsc(lastVocalUtterance + compareTone,fs);

Call `spectrogram`

to more closely inspect the frequency content of the singing. Use a frame size of `250`

samples and an overlap of `225`

samples or 90%. Use `4096`

DFT points for the transform. The `spectrogram`

reveals that the vocal recording is actually a set of complex harmonic tones composed of multiple frequencies.

`spectrogram(audioIn,250,225,4096,fs,'yaxis')`

## Input Arguments

`activations`

— CREPE network output

*N*-by-`360`

matrix

Audio frames generated from a `crepe`

pretrained network, specified as an *N*-by-`360`

matrix, where *N* is the number of generated frames.

**Data Types: **`single`

| `double`

`TH`

— Confidence threshold

`0.5`

(default) | nonnegative scalar in the range [0,1)

Confidence threshold for each value of `f0`

, specified as the
comma-separated pair consisting of `'ConfidenceThreshold'`

and a scalar
in the range [0,1).

To disable thresholding, set `TH`

to `0`

.

**Note**

If the maximum value of the corresponding `activations`

vector
is less than `TH`

, `f0`

is
`NaN`

.

**Data Types: **`single`

| `double`

## Output Arguments

`f0`

— Estimated fundamental frequency

*N*-by-`1`

vector

Estimated fundamental frequency in Hertz, returned as an
*N*-by-`1`

vector, where *N* is the
number of generated frames.

**Data Types: **`single`

## References

[1] Kim, Jong Wook, Justin Salamon,
Peter Li, and Juan Pablo Bello. “Crepe: A Convolutional Representation for Pitch Estimation.”
In *2018 IEEE International Conference on Acoustics, Speech and Signal
Processing (ICASSP)*, 161–65. Calgary, AB: IEEE, 2018.
https://doi.org/10.1109/ICASSP.2018.8461329.

## Extended Capabilities

### C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

### GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

This function fully supports GPU arrays. For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

## Version History

**Introduced in R2021a**

## See Also

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