writeall
Description
writeall(
writes the data from the audio datastore ADS
,outputLocation
)ADS
to files located at
outputLocation
.
writeall(
writes the data with additional options specified by one or more name-value
arguments.ADS
,outputLocation
,Name=Value
)
Example: writeall(ADS,outputLocation,OutputFormat="flac")
writes the
data to FLAC files.
Examples
Write Audio Data Set to New Location
Create an audioDatastore
object that points to the WAV audio samples included with Audio Toolbox™. The audioDatastore
object includes read-only properties indicating the supported file formats, and the default output format (WAV).
folder = fullfile(matlabroot,'toolbox','audio','samples'); ads = audioDatastore(folder,'FileExtensions','.wav')
ads = audioDatastore with properties: Files: { ' .../build/matlab/toolbox/audio/samples/Ambiance-16-44p1-mono-12secs.wav'; ' .../matlab/toolbox/audio/samples/AudioArray-16-16-4channels-20secs.wav'; ' .../toolbox/audio/samples/ChurchImpulseResponse-16-44p1-mono-5secs.wav' ... and 17 more } Folders: { ' .../filer/batfs1904-0/Bdoc24a.2528353/build/matlab/toolbox/audio/samples' } AlternateFileSystemRoots: {} OutputDataType: 'double' OutputEnvironment: 'cpu' Labels: {} SupportedOutputFormats: ["wav" "flac" "ogg" "opus" "mp3" "mp4" "m4a"] DefaultOutputFormat: "wav"
Write the audio data set to your current folder. Save all files in the default (WAV) format.
outputLocation = pwd; writeall(ads,outputLocation)
The folder, samples
, and the audio files that the folder contains have been written to your current folder.
dir samples
. .. Ambiance-16-44p1-mono-12secs.wav AudioArray-16-16-4channels-20secs.wav ChurchImpulseResponse-16-44p1-mono-5secs.wav Click-16-44p1-mono-0.2secs.wav Counting-16-44p1-mono-15secs.wav Engine-16-44p1-stereo-20sec.wav FemaleSpeech-16-8-mono-3secs.wav Heli_16ch_ACN_SN3D.wav JetAirplane-16-11p025-mono-16secs.wav Laughter-16-8-mono-4secs.wav MainStreetOne-16-16-mono-12secs.wav NoisySpeech-16-22p5-mono-5secs.wav Rainbow-16-8-mono-114secs.wav RainbowNoisy-16-8-mono-114secs.wav RockGuitar-16-44p1-stereo-72secs.wav SpeechDFT-16-8-mono-5secs.wav TrainWhistle-16-44p1-mono-9secs.wav Turbine-16-44p1-mono-22secs.wav WashingMachine-16-44p1-stereo-10secs.wav multipleSounds-16-16-mono-18secs.wav
Pre-Extract Features from Audio Data Set
You can use pre-extracted features to reduce iteration time when developing a machine learning or deep learning system. It is also a common practice to use pre-extracted features for unsupervised learning tasks such as similarity clustering, and for content-based indexing tasks such as music information retrieval (MIR).
Create an audioDatastore
object that points to the audio samples included with Audio Toolbox™.
folder = fullfile(matlabroot,"toolbox","audio","samples"); ads = audioDatastore(folder)
ads = audioDatastore with properties: Files: { ' .../build/matlab/toolbox/audio/samples/Ambiance-16-44p1-mono-12secs.wav'; ' .../matlab/toolbox/audio/samples/AudioArray-16-16-4channels-20secs.wav'; ' .../toolbox/audio/samples/ChurchImpulseResponse-16-44p1-mono-5secs.wav' ... and 36 more } Folders: { ' .../filer/batfs1904-0/Bdoc24a.2528353/build/matlab/toolbox/audio/samples' } AlternateFileSystemRoots: {} OutputDataType: 'double' OutputEnvironment: 'cpu' Labels: {} SupportedOutputFormats: ["wav" "flac" "ogg" "opus" "mp3" "mp4" "m4a"] DefaultOutputFormat: "wav"
Create a custom write function that extracts mel frequency cepstral coefficients (mfcc
) from the audio and writes them to a MAT file. The function definition is located at the end of this example.
function myWriter(audioIn,info,~) fs = info.ReadInfo.SampleRate; % Extract MFCC [coeffs,delta,deltaDelta] = mfcc(audioIn,fs); % Replace the file extension of the suggested output name with MAT. filename = strrep(info.SuggestedOutputName,".wav",".mat"); % Save the MFCC coefficients to the MAT file. save(filename,"coeffs","delta","deltaDelta") end
Define the output location for the extracted features.
outputLocation = pwd;
Call the writeall
function with the audioDatastore
object, output location, and custom write function. Also specify the suffix _MFCC
to the file names.
tic writeall(ads,outputLocation,"WriteFcn",@myWriter,"FilenameSuffix","_MFCC") fprintf("Data set creation completed (%0.0f seconds)\n",toc)
Data set creation completed (15 seconds)
You have now created a data set consisting of MFCCs for each audio file.
fds = fileDatastore(pwd,"ReadFcn",@load,"FileExtensions",".mat","IncludeSubfolders",true)
fds = FileDatastore with properties: Files: { ' .../audio-ex80013303/samples/Ambiance-16-44p1-mono-12secs_MFCC.mat'; ' .../audio-ex80013303/samples/AudioArray-16-16-4channels-20secs_MFCC.mat'; ' .../samples/ChurchImpulseResponse-16-44p1-mono-5secs_MFCC.mat' ... and 36 more } Folders: { '/tmp/Bdoc24a_2528353_1284000/tp22c0a96d/audio-ex80013303' } UniformRead: 0 ReadMode: 'file' BlockSize: Inf PreviewFcn: @load SupportedOutputFormats: ["txt" "csv" "dat" "asc" "xlsx" "xls" "parquet" "parq" "png" "jpg" "jpeg" "tif" "tiff" "wav" "flac" "ogg" "opus" "mp3" "mp4" "m4a"] ReadFcn: @load AlternateFileSystemRoots: {}
Helper Function
function myWriter(audioIn,info,~) fs = info.ReadInfo.SampleRate; [coeffs,delta,deltaDelta] = mfcc(audioIn,fs); filename = strrep(info.SuggestedOutputName,".wav",".mat"); save(filename,"coeffs","delta","deltaDelta") end
Augment Audio Data Set
Create an audioDatastore
object that points to the audio samples included with Audio Toolbox™.
folder = fullfile(matlabroot,"toolbox","audio","samples"); ads = audioDatastore(folder);
Create an audioDataAugmenter
object that outputs two augmentations for every input signal.
augmenter = audioDataAugmenter(NumAugmentations=2);
Define a custom write function, myWriter
, that applies the audioDataAugmenter
object to an audio file and writes the resulting new signals to separate files.
Call the writeall
function to create a new augmented data set. To speed up processing, set UseParallel
to true
.
outputLocation = pwd; writeall(ads,outputLocation,FilenameSuffix="_Aug", ... UseParallel=true,WriteFcn=@(x,y,z,a)myWriter(x,y,z,augmenter))
Create a new datastore that points to the augmented audio data set.
adsAug = audioDatastore(outputLocation,IncludeSubfolders=true);
myWriter
Helper Function
function myWriter(audioIn,info,fileExtension,varargin) % Create convenient variables for the augmenter and sample rate augmenter = varargin{1}; fs = info.ReadInfo.SampleRate; % Perform augmentation augmentations = augment(augmenter,audioIn,fs); for ii = 1:augmenter.NumAugmentations x = augmentations.Audio{ii}; % Protect against clipping if any(x<-1|x>1) x = x./max(abs(x)); end % Update the audio file name to include the augmentation number filename = insertBefore(info.SuggestedOutputName,("."+fileExtension),string(ii)); % Write the audio file audiowrite(filename,x,fs) end end
Segment Audio Data
Use the detectSpeech
and writeall
functions to create a new audio data set that contains isolated speech segments.
Create an audioDatastore
object that points to the audio samples included with this example.
ads = audioDatastore(pwd)
ads = audioDatastore with properties: Files: { ' .../tp2fa81b82/audio-ex78151030/KeywordSpeech-16-16-mono-34secs.flac'; '/tmp/Bdoc24a_2528353_1292256/tp2fa81b82/audio-ex78151030/Plosives.wav'; '/tmp/Bdoc24a_2528353_1292256/tp2fa81b82/audio-ex78151030/Sibilance.wav' } Folders: { '/tmp/Bdoc24a_2528353_1292256/tp2fa81b82/audio-ex78151030' } AlternateFileSystemRoots: {} OutputDataType: 'double' OutputEnvironment: 'cpu' Labels: {} SupportedOutputFormats: ["wav" "flac" "ogg" "opus" "mp3" "mp4" "m4a"] DefaultOutputFormat: "wav"
Define a custom write function that first determines the regions of speech in the audio signals read from the datastore, then writes the individual regions of speech to separate files. Append the region number to the file names. The function definition is located at the end of this example.
function myWriter(audioIn,info,fileExtension) fs = info.ReadInfo.SampleRate; % Get indices corresponding to regions of speech idx = detectSpeech(audioIn,fs); % For each region of speech for ii = 1:size(idx,1) x = audioIn(idx(ii,1):idx(ii,2),:); % Create a unique file name filename = insertBefore(info.SuggestedOutputName,("."+fileExtension),string(ii)); % Write the detected region of speech audiowrite(filename,x,fs) end end
Call the writeall
function using the custom write function to create a new data set that consists of the isolated speech segments. Create a folder named segmented
in your temporary directory and then write the data to that folder.
outputLocation = fullfile(tempdir,"segmented"); writeall(ads,outputLocation,'WriteFcn',@myWriter)
Create a new audioDatastore
object that points to the segmented data set.
adsSegmented = audioDatastore(outputLocation,"IncludeSubfolders",true)
adsSegmented = audioDatastore with properties: Files: { ' .../segmented/audio-ex78151030/KeywordSpeech-16-16-mono-34secs1.wav'; ' .../segmented/audio-ex78151030/KeywordSpeech-16-16-mono-34secs10.wav'; ' .../segmented/audio-ex78151030/KeywordSpeech-16-16-mono-34secs11.wav' ... and 24 more } Folders: { '/tmp/Bdoc24a_2528353_1292256/segmented' } AlternateFileSystemRoots: {} OutputDataType: 'double' OutputEnvironment: 'cpu' Labels: {} SupportedOutputFormats: ["wav" "flac" "ogg" "opus" "mp3" "mp4" "m4a"] DefaultOutputFormat: "wav"
Read a sample from the datastore and listen to it.
[audioIn,adsInfo] = read(adsSegmented); sound(audioIn,adsInfo.SampleRate)
Supporting Function
function myWriter(audioIn,info,fileExtension) fs = info.ReadInfo.SampleRate; idx = detectSpeech(audioIn,fs); for ii = 1:size(idx,1) x = audioIn(idx(ii,1):idx(ii,2),:); filename = insertBefore(info.SuggestedOutputName,("."+fileExtension),string(ii)); audiowrite(filename,x,fs) end end
Clean Audio Data Set
Audio data sets, especially open-source audio data sets, might have inconsistent sampling rates, numbers of channels, or durations. They might also contain garbage data, such as clips that are labeled as containing speech but contain silence.
It is often a first step in machine learning and deep learning workflows to clean the audio data set. This is particularly important for the validation and test data sets. Common types of cleaning include resampling, converting to mono or stereo, trimming or expanding the duration of clips to a consistent length, removing periods of silence, removing background noise, or gain normalization.
In this example, you clean an audio data set so that all the files have a sample rate of 16 kHz, are mono, are in the FLAC format, and are normalized such that the max absolute magnitude of a signal is 1
.
Create an audioDatastore
object that points to the audio samples included with Audio Toolbox™.
folder = fullfile(matlabroot,"toolbox","audio","samples"); ads = audioDatastore(folder);
Define a function, myTransform
, that applies a sequence of operations on the audio data. Create a transform datastore object that applies the cleaning operations.
adsTransform = transform(ads,@myTransform,IncludeInfo=true);
Call writeall
on the transform datastore object to create the clean data set. Specify the format as FLAC
. Write the data set to your current folder.
outputLocation = pwd;
writeall(adsTransform,outputLocation,OutputFormat="flac")
Create a new datastore object that points to the clean data set.
adsClean = audioDatastore(outputLocation,IncludeSubfolders=true);
myTransform
Supporting Function
function [audioOut,adsInfo] = myTransform(audioIn,adsInfo) fs = adsInfo.SampleRate; desiredFs = 16e3; % Convert to mono x = mean(audioIn,2); % Resample to 16 kHz y = resample(x,desiredFs,fs); adsInfo.SampleRate = desiredFs; % Normalize so that the max absolute value of a signal is 1 audioOut = y/max(abs(y)); end
Input Arguments
ADS
— Audio datastore
audioDatastore
object
Audio datastore, specified as an audioDatastore
object.
outputLocation
— Folder location to write data
character vector | string
Folder location to write data, specified as a character vector or string. You can
specify a full or relative path in outputLocation
.
Example: outputLocation = "../../dir/data"
Example: outputLocation = "C:\Users\MyName\Desktop"
Data Types: char
| string
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Example: FolderLayout="flatten"
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: 'FolderLayout','flatten'
FolderLayout
— Layout of files in output folder
"duplicate"
(default) | "flatten"
Layout of files in output folder, specified as "duplicate"
or
"flatten"
.
"duplicate"
–– Replicate the folder structure of the data that the audio datastore points to. Specify theFolderLayout
as"duplicate"
to maintain correspondence between the input and output data sets."flatten"
–– Write all the files from the input to the specified output folder without any intermediate folders.
Data Types: char
| string
OutputFormat
— Output file format
"wav"
(default) | "flac"
| "ogg"
| "opus"
| "mp3"
| "mp4"
| "m4a"
Output file format, specified as "wav"
,
"flac"
, "ogg"
, "opus"
,
"mp3"
, "mp4"
, or
"m4a"
.
Data Types: char
| string
BitsPerSample
— Number of output bits per sample
16
(default) | 8
| 24
| 32
| 64
Number of output bits per sample, specified as an integer.
Dependencies
To enable this name-value pair argument, set OutputFormat
to "wav"
or "flac"
.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
BitRate
— Kilobits per second (kbit/s)
128
(default) | 64
| 96
| 160
| 192
| 256
| 320
Number of kilobits per second (kbit/s) used to compress audio files, specified as
an integer. On Windows® 7 or later, the only valid values are 96
,
128
, 160
, and 192
.
In general, a larger BitRate
value results in higher
compression quality.
Dependencies
To enable this name-value pair argument, set OutputFormat
to "m4a"
or "mp4"
.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
Quality
— Quality setting for compression
75 (default) | value in the range [0, 100]
Quality setting for MP3, OGG, or OPUS files, specified as a number in the range [0, 100], where 0 is lower quality and higher compression, and 100 is higher quality and lower compression.
Dependencies
To enable this name-value pair argument, set OutputFormat
to "mp3"
, "ogg"
or
"opus"
.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
FilenamePrefix
— Prefix added to file name
character vector | string
Prefix added to file name, specified a character vector or string.
The writeall
function adds the specified prefix to the output
file names. For example, the following code adds today's date as the prefix to all the
output file
names:
prefixText = string(datetime("today")); writeall(ADS,"C:\myFolder",FilenamePrefix=prefixText);
Data Types: char
| string
FilenameSuffix
— Suffix added to file name
character vector | string
Suffix added to the file name, specified as character vector or string. The file name suffix is applied before the file extension.
The writeall
function adds the specified suffix to the output
file names. For example, the following code adds the descriptive text
"clean"
as the suffix to all the output file
names:
writeall(ADS,"C:\myFolder",FilenameSuffix="clean");
Data Types: char
| string
UseParallel
— Indicator to write in parallel
false
(default) | true
Indicator to write in parallel, specified as false
or
true
.
By default, the writeall
function writes in serial. If you
set UseParallel
to true
, then the
writeall
function writes the output files in parallel.
Note
Writing in parallel requires Parallel Computing Toolbox™.
Data Types: logical
WriteFcn
— Custom write function
function handle
Custom write function, specified as a function handle. The specified function is
responsible for creating the output files. You can use WriteFcn
to write data in a variety of formats, even if writeall
does not
directly support the output format.
Function Signature
The custom write function requires three input arguments:
audioIn
, info
, and
suggestedOutputType
. The function can also accept additional
inputs, such as name-value pairs, after the first three required inputs.
function myWriter(audioIn,info,suggestedOutputType,varargin)
audioIn
contains data read from the input datastoreADS
.info
is an object of typematlab.io.datastore.WriteInfo
with fields listed in the table.Field Description Type ReadInfo
The second output of the read
method.struct
SuggestedOutputName
A fully qualified, globally unique file name that meets the location and naming requirements. string
Location
The specified outputLocation
passed towriteall
.string
suggestedOutputType
–– Suggested output file type.
Example Function
A simple write function that resamples audio to 44.1 kHz before writing.
function myWriter(data,info,~) fs = info.ReadInfo.SampleRate; desiredFs = 44.1e3; data = resample(data,desiredFs,fs); audiowrite(writeInfo.SuggestedOutputName,data,desiredFs); end
myWriter
as in the writeall
function,
use these
commands:ads = audioDatastore(location);
outputLocation = "C:/tmp/MyData";
writeall(ads,outputLocation,WriteFcn=@myWriter)
Data Types: function_handle
Version History
Introduced in R2020aR2024a: Support for writing MP3 files
The audioDatastore
writeall
function supports writing MP3 files
(.mp3
).
R2022b: Support for OPUS audio file format
The audioDatastore
writeall
function supports OPUS file format
(.opus
).
See Also
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