Vosklet/usage/README.md

API interface

JS window object

Function signature	Description
Promise<Module> loadBR()	Load Emscripten's Module

Shared interface

Function signature	Description
delete()	Delete this object, see why this is neccessary.

Module object

Function signature	Description
Promise<Model> makeModel(path: string, url: string, id: string) Promise<SpkModel> makeSpkModel(path: string, url: string, id: string)	Make a Model or SpkModel, model files must be directly under the model root, and compressed model must be in .tgz format. If: - path contains valid model files and id is the same, there will not be a fetch from url. - path doesn't contain valid model files, or if it contains valid model files but id is different, there will be a fetch from url, and the model is stored with id.
Promise<Recognizer> makeRecognizer(model: Model, sampleRate: float)	Make a Recognizer, it will use model's thread if it's the first user of model, else it will use a new thread.
setLogLevel(lvl: int)	Set Vosk's log level (default: 0: Info) -2: Error -1: Warning 1: Verbose 2: More verbose 3: Debug
revokeURLs()	Revoke the Blob URLs of pthread worker and worklet processor
cleanUp()	A convenience function that call revokeURLs() and delete() on all objects. You should put this at the end of your program!

Recognizer object

Function signature	Description
Promise<AudioWorkletNode> getNode(ctx: AudioContext, channelIndex = 0: int)	Get a pass-through node that recognize audio and is connectable to a processing graph. It has 1 input and 1 output, channelIndex must point to a 16-bit mono channel of the input
recognize(buf: AudioBuffer, channelIndex = 0: int)	Recognize an AudioBuffer, usually from something like BaseAudioContext.decodeAudioData(), channelIndex must point to a 16-bit mono channel of buf
setPartialWords(partialWords: bool)	Return words' information in a partialResult event (default: false)
setWords(words: bool)	Return words' information in a result event (default: false)
setNLSML(nlsml: bool)	Return result and partialResult in NLSML form (default: false)
setMaxAlternatives(alts: int)	Set the max number of alternatives for result event (default: false)
setGrm(grm: string)	Add grammar to the recognizer (default: none)
setSpkModel(mdl: SpkModel)	Set the speaker model of the recognizer (default: none)

Event	Description
partialResult	There is a partial recognition result, check the event's "details" property
result	There is a full recognition result, check the event's "details" property

User agent notes

SharedArrayBuffer

Browser-recognizer require SharedArrayBuffer to share thread's data, so these response headers must be set:

• Cross-Origin-Embedder-Policy ---> require-corp
• Cross-Origin-Opener-Policy ---> same-origin

If you can't set them, you may use a HACKY workaround at src/addCOI.js.

Origin Private Filesystem (OPFS)

Browser-recognizer needs the Emscripten WASMFS' OPFS to store its model, IDBFS was considered, but dropped because there is no direct way to read from IDBFS to C++ without copying to MEMFS (basically RAM). For safety with this, always:

• Try catch window.loadBR() to to check for OPFS availability.
• Check if there is enough space via navigator.storage.estimate() for TWICE THE MODEL SIZE before calling Module.makeModel

Compilation

Changing any option to non-default values requires recompilation

git clone --depth=1 https://github.com/msqr1/Browser-recognizer &&
cd Browser-recognizer &&
[Options] make

Option	Description	Default value
MAX_MEMORY	Set max memory, valid suffixes: kb, mb, gb, tb or none (bytes)	300mb, as recommended
MAX_THREADS	Set the max number of thread (2 min)	2 (1 OPFS thread + 1 model/recognizer thread)
COMPILE_JOBS	Set the number of jobs (threads) when compiling	$(nproc)
EMSDK	Set EMSDK's path (will install EMSDK in root folder if unset)	../emsdk