Synthesizer Methods
The synthesizer resource is the half of an MRCP session responsible for text-to-speech: it turns supplied text or SSML into audio and manages that playback while it is in progress—pausing, resuming, stopping, and yielding to the caller when barge-in occurs. The methods below are the control messages a client sends to drive that resource.
These methods are defined in IETF RFC 4463 (MRCPv1) and IETF RFC 6787 (MRCPv2). The protocol evolved between the two versions, and not every method is part of both specifications or supported on every platform. The table records, for each method, whether it is part of the MRCPv1 specification, the MRCPv2 specification, and whether it is supported on Capacity Private Cloud. Select any method name for its full reference, including the headers it accepts and the responses it returns.
SET-PARAMS and GET-PARAMS are generic methods shared by every MRCP resource rather than synthesizer-specific ones; they are listed here for completeness.
Method support by MRCP version
Method | MRCP V1 | MRCP V2 | Platform Support |
✓ | ✓ | ✓ | |
✓ | ✓ | ✓ | |
✓ | ✓ | ✓ | |
✓ | ✓ | ✓ | |
✓ | ✓ | ✓ | |
✓ | ✓ | ✓ | |
✓ | ✓ | ✓ | |
✓ | ✓ | — | |
— | ✓ | — |
✓ = defined or supported | — = not defined in that version, or not supported on the platform
Support notes
DEFINE-LEXICON. This method—which loads a custom pronunciation lexicon for the synthesizer to apply—was introduced with MRCPv2 and is not part of the MRCPv1 specification. It is not currently supported on Capacity Private Cloud; manage pronunciations through SSML <phoneme> markup or platform pronunciation settings instead.
CONTROL. The CONTROL method, which adjusts an in-progress SPEAK request (for example changing rate or volume, or jumping within the prompt), is defined in both MRCPv1 and MRCPv2 but is not currently supported on the platform. To change speech that is already playing, stop the current SPEAK and issue a new one with the desired parameters.