feat(audio): allow sending continuous audio

[mariotaku]

Description

When host has no audio playing, Sunshine won't send audio. For webOS client, when surround sound is used, video will freeze when there is no audio coming in.

This PR allows the host to send empty audio frame in such case, mitigating webOS freezing issue.

Screenshot

Issues Fixed or Closed

Roadmap Issues

Type of Change

• feat: New feature (non-breaking change which adds functionality)
• fix: Bug fix (non-breaking change which fixes an issue)
• docs: Documentation only changes
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semicolons, etc.)
• refactor: Code change that neither fixes a bug nor adds a feature
• perf: Code change that improves performance
• test: Adding missing tests or correcting existing tests
• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Other changes that don't modify src or test files
• revert: Reverts a previous commit
• BREAKING CHANGE: Introduces a breaking change (can be combined with any type above)

Checklist

• Code follows the style guidelines of this project
• Code has been self-reviewed
• Code has been commented, particularly in hard-to-understand areas
• Code docstring/documentation-blocks for new or existing methods/components have been added or updated
• Unit tests have been added or updated for any new or modified functionality

AI Usage

• None: No AI tools were used in creating this PR
• Light: AI provided minor assistance (formatting, simple suggestions)
• Moderate: AI helped with code generation or debugging specific parts
• Heavy: AI generated most or all of the code changes

[andygrundman]

LGTM, nice and simple, and seems fine as a hidden setting. I guess the only downside is that the audio stream is CBR so all those zeroes still consume 512k/1.5Mb/2Mb.

[codecov]

Bundle Report

Bundle size has no change ✅

[ReenigneArcher]

seems fine as a hidden setting.

I believe this a setting that comes from the client itself, right?

[codecov]

Codecov Report

❌ Patch coverage is 0% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 11.97%. Comparing base (246d8f1) to head (e3069d9).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/platform/windows/audio.cpp	0.00%	8 Missing ⚠️
src/audio.cpp	0.00%	3 Missing ⚠️
src/rtsp.cpp	0.00%	3 Missing ⚠️
src/nvhttp.cpp	0.00%	1 Missing ⚠️
src/platform/linux/audio.cpp	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4261      +/-   ##
==========================================
- Coverage   11.98%   11.97%   -0.01%     
==========================================
  Files          87       87              
  Lines       17572    17581       +9     
  Branches     8076     8082       +6     
==========================================
  Hits         2106     2106              
- Misses      14569    14578       +9     
  Partials      897      897              

Flag	Coverage Δ
Linux-AppImage	11.48% <0.00%> (-0.01%)	⬇️
Windows-AMD64	13.25% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/audio.h	100.00% <ø> (ø)
src/platform/common.h	24.13% <ø> (ø)
src/nvhttp.cpp	18.07% <0.00%> (-0.03%)	⬇️
src/platform/linux/audio.cpp	10.63% <0.00%> (ø)
src/audio.cpp	22.05% <0.00%> (-0.17%)	⬇️
src/rtsp.cpp	1.04% <0.00%> (-0.01%)	⬇️
src/platform/windows/audio.cpp	25.13% <0.00%> (-0.19%)	⬇️

[mariotaku]

@ReenigneArcher Yes. Only when the client requests continuousAudio=1 via launch request, Sunshine will feed empty audio frame when it's not able to capture one.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[ns6089]

It's simple because it has an inherent buffer underrun - buffer is only filled when WaitForSingleObjectEx() times out and this function always overshoots. But it it fixes your issue...