SynthesisCallback
public
interface
SynthesisCallback
| android.speech.tts.SynthesisCallback |
A callback to return speech data synthesized by a text to speech engine.
The engine can provide streaming audio by calling
start(int, int, int), then audioAvailable(byte, int, int) until all audio has been provided, then finally
done().
error() can be called at any stage in the synthesis process to
indicate that an error has occurred, but if the call is made after a call
to done(), it might be discarded.
done() must be called at the end of synthesis, regardless of errors.
All methods can be only called on the synthesis thread.
Summary
Public methods | |
|---|---|
abstract
int
|
audioAvailable(byte[] buffer, int offset, int length)
The service should call this method when synthesized audio is ready for consumption. |
abstract
int
|
done()
The service should call this method when all the synthesized audio for a request has been
passed to |
abstract
void
|
error(int errorCode)
The service should call this method if the speech synthesis fails. |
abstract
void
|
error()
The service should call this method if the speech synthesis fails. |
abstract
int
|
getMaxBufferSize()
|
abstract
boolean
|
hasFinished()
Check if |
abstract
boolean
|
hasStarted()
Check if |
default
void
|
rangeStart(int markerInFrames, int start, int end)
The service may call this method to provide timing information about the spoken text. |
abstract
int
|
start(int sampleRateInHz, int audioFormat, int channelCount)
The service should call this when it starts to synthesize audio for this request. |
Public methods
audioAvailable
public abstract int audioAvailable (byte[] buffer,
int offset,
int length)The service should call this method when synthesized audio is ready for consumption.
This method should only be called on the synthesis thread, while in TextToSpeechService.onSynthesizeText(SynthesisRequest, SynthesisCallback).
| Parameters | |
|---|---|
buffer |
byte: The generated audio data. This method will not hold on to buffer, so the
caller is free to modify it after this method returns. |
offset |
int: The offset into buffer where the audio data starts. |
length |
int: The number of bytes of audio data in buffer. This must be less than or
equal to the return value of getMaxBufferSize(). |
| Returns | |
|---|---|
int |
TextToSpeech.SUCCESS, TextToSpeech.ERROR or TextToSpeech.STOPPED. |
done
public abstract int done ()
The service should call this method when all the synthesized audio for a request has been
passed to audioAvailable(byte, int, int).
This method should only be called on the synthesis thread, while in TextToSpeechService.onSynthesizeText(SynthesisRequest, SynthesisCallback).
This method has to be called if start(int, int, int) and/or error() was called.
| Returns | |
|---|---|
int |
TextToSpeech.SUCCESS, TextToSpeech.ERROR or TextToSpeech.STOPPED. |
error
public abstract void error (int errorCode)
The service should call this method if the speech synthesis fails.
This method should only be called on the synthesis thread, while in TextToSpeechService.onSynthesizeText(SynthesisRequest, SynthesisCallback).
| Parameters | |
|---|---|
errorCode |
int: Error code to pass to the client. One of the ERROR_ values from TextToSpeech
Value is TextToSpeech.ERROR_SYNTHESIS, TextToSpeech.ERROR_SERVICE, TextToSpeech.ERROR_OUTPUT, TextToSpeech.ERROR_NETWORK, TextToSpeech.ERROR_NETWORK_TIMEOUT, TextToSpeech.ERROR_INVALID_REQUEST, or TextToSpeech.ERROR_NOT_INSTALLED_YET |
error
public abstract void error ()
The service should call this method if the speech synthesis fails.
This method should only be called on the synthesis thread, while in TextToSpeechService.onSynthesizeText(SynthesisRequest, SynthesisCallback).
getMaxBufferSize
public abstract int getMaxBufferSize ()
| Returns | |
|---|---|
int |
the maximum number of bytes that the TTS engine can pass in a single call of audioAvailable(byte, int, int). Calls to audioAvailable(byte, int, int) with data lengths larger than this
value will not succeed. |
hasFinished
public abstract boolean hasFinished ()
Check if done() was called or not.
This method should only be called on the synthesis thread, while in TextToSpeechService.onSynthesizeText(SynthesisRequest, SynthesisCallback).
Useful for checking if a fallback from network request is possible.
| Returns | |
|---|---|
boolean |
|
hasStarted
public abstract boolean hasStarted ()
Check if start(int, int, int) was called or not.
This method should only be called on the synthesis thread, while in TextToSpeechService.onSynthesizeText(SynthesisRequest, SynthesisCallback).
Useful for checking if a fallback from network request is possible.
| Returns | |
|---|---|
boolean |
|
rangeStart
public void rangeStart (int markerInFrames,
int start,
int end)The service may call this method to provide timing information about the spoken text.
Calling this method means that at the given audio frame, the given range of the input is
about to be spoken. If this method is called the client will receive a callback on the
listener (UtteranceProgressListener.onRangeStart) at the moment that frame has been
reached by the playback head.
This information can be used by the client, for example, to highlight ranges of the text while it is spoken.
The markerInFrames is a frame index into the audio for this synthesis request, i.e. into
the concatenation of the audio bytes sent to audioAvailable for this synthesis request. The
definition of a frame depends on the format given by start(int, int, int). See AudioFormat
for more information.
This method should only be called on the synthesis thread, while in TextToSpeechService.onSynthesizeText(SynthesisRequest, SynthesisCallback).
| Parameters | |
|---|---|
markerInFrames |
int: The position in frames in the audio where this range is spoken. |
start |
int: The start index of the range in the input text. |
end |
int: The end index (exclusive) of the range in the input text. |
start
public abstract int start (int sampleRateInHz,
int audioFormat,
int channelCount)The service should call this when it starts to synthesize audio for this request.
This method should only be called on the synthesis thread, while in TextToSpeechService.onSynthesizeText(SynthesisRequest, SynthesisCallback).
| Parameters | |
|---|---|
sampleRateInHz |
int: Sample rate in HZ of the generated audio. |
audioFormat |
int: Audio format of the generated audio. Must be one of AudioFormat.ENCODING_PCM_8BIT or AudioFormat.ENCODING_PCM_16BIT. Can also be
AudioFormat.ENCODING_PCM_FLOAT when targetting Android N and above.
Value is AudioFormat.ENCODING_PCM_8BIT, AudioFormat.ENCODING_PCM_16BIT, or AudioFormat.ENCODING_PCM_FLOAT |
channelCount |
int: The number of channels. Must be 1 or 2.
Value is between 1 and 2 inclusive |
| Returns | |
|---|---|
int |
TextToSpeech.SUCCESS, TextToSpeech.ERROR or TextToSpeech.STOPPED. |