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Sapi 5 performance issues in nvda 2025 beta #17967

@acerbt

Description

@acerbt

Steps to reproduce:

First, set the synthesizer for NVDA to sapi5.
then, try some of the following.
Go into voice settings, and with rate boost on, change the rate between 0 and 100 rapidly using home and end. The reasoning behind this will become clear later.
also try navigating between multiple open apps with alt tab, and do other actions which you may perform several times quickly, such as navigating through a document by word or character.

Actual behavior:

As this is an audio issue, speech viewer outputs won't help much here. In the nvda 2025 beta, if speech from sapi is ever cut off from pressing control, another speech event, etc, there is a chance, depending on what, if any, of the previous speech utterance was not yet spoken, that the speech will sort of skip, and play a small fragment of something later in the utterance, before it gets replaced with new speech or is silenced. The example of going between rates 0 and 100 cause this, if you change the rate to 100 from 0, while the sapi voice is still outputing the z in 0. It can skip ahead and play a fragment of the e segment, or even the o in some cases. It is fairly quick, so might be hard to pick up on without listening hard. Similar things occure with other cases where speech is cut off, though in many of those, it's just a small click that is heard as things transition.

Expected behavior:

The speech should be able to smoothly stop playing back, and begin speaking anything new, if there is any, or go silent when control is pressed, without any clicks/ pops.

nvda.log

NVDA logs, crash dumps and other attachments:

System configuration

NVDA installed/portable/running from source:

NVDA is installed

NVDA version:

2025.1beta1 (2025.1.0.36065)

Windows version:

Windows 11 24H2 (AMD64) build 26100.3775

Name and version of other software in use when reproducing the issue:

n/a?

Other information about your system:

Other questions

Does the issue still occur after restarting your computer?

Yes

Have you tried any other versions of NVDA? If so, please report their behaviors.

I previously used the latest nvda 2024 build, which as of writing is 2024.4.2. This version does properly handle speech output, without inserting any extra artafacts (pops, clicks, etc) when stopping speech with control or cutting off an utterance to read something else.

If NVDA add-ons are disabled, is your problem still occurring?

This happens with all add-ons disabled.

Does the issue still occur after you run the COM Registration Fixing Tool in NVDA's tools menu?

Yes

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    component/speech-synth-driversp5https://github.com/nvaccess/nvda/blob/master/projectDocs/issues/triage.md#prioritytriagedHas been triaged, issue is waiting for implementation.

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