TTS engine properties SpeedNorm and VolumeNorm for SAPI 4 inconsistent

The information in this article applies to:

Symptoms

Setting a SAPI 4 TTS engine speed and volume using the SpeedNorm and VolumeNorm properties results in inconsistent settings.

Cause

SAPI 4 specification allows for large range (DWORD) of values for the vendor to support scaling speed and volume of synthesis playback. The excessive range was addressed in the SAPI 5 specification with smaller ranges. The ChantTTS component provides a SpeedNorm and VolumeNorm property to be able to map SAPI 4 ranges to the SAPI 5 ranges so an application can use the normalized property and not have to check whether a TTS engine (i.e., voice) is SAPI 4 or SAPI 5.

SAPI 4 doesn't always set the value exactly as requested, however, the mapping mechanism has been updated to ensure the requested range is correct in all situations.

Status

Fixed in SpeechKit 4 build 4.0.82.0.

Component Formats Impacted

All formats.