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PCSX2-Reliquary v1.8.2 has been released, a fork of PCSX2 focusing on accurate emulation of non-retail PS2 hardware. The update introduces a low-latency audio sync mode that minimizes delays at the expense of audio quality during slowdowns. Testing showed improved performance, with lower latency results on Linux systems. Additionally, two new audio backends for Windows were added: WASAPI Exclusive Mode, which offers very low latency but lacks mixer support, and IAudioClient3, which provides similar benefits if hardware supports WaveRT. This release enhances audio performance, especially for rhythm games, while maintaining compatibility across platforms.
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The release of PCSX2-Reliquary v1.8.2 is here! PCSX2 Reliquary is a fork of PCSX2 that concentrates on precise emulation of security flows and unique hardware derived from the PS2. It aims at platforms and software beyond the typical retail console route, including systems like the Konami Python 1 & 2, and the Namco System families.
Changelog for PCSX2-Reliquary:
Summary of Updates
Introduced a low-latency audio sync mode featuring tight rate control and resampling. This new sync mode maintains the correction window capped at +/-1% target speed, allowing for tighter buffers and significantly lower latency, albeit with a potential drop in audio quality during slowdowns.
In testing, I found that requesting lower latency than what cubeb indicates as the minimum actually leads to those latencies being achieved.
For example, on my Linux system, all audio devices are optimized for low-latency playback and can run PulseAudio with only a 64 frame quant (~0.02ms). Cubeb indicates a minimum of 25ms for the Pulse backend, which seems excessive, even for an untuned system.
When I disregarded this and requested 1ms from cubeb, the measured rate turned out to be around ~120 frames, or ~4ms. This is a significant improvement compared to previous versions.
Currently in PCSX2, TimeStretch is utilized via the SoundTouch library with ::setTempo. This feature works excellently during fast-forward and slow-motion, preserving the pitch of the audio while maintaining clarity. However, with the existing defaults, SoundTouch is set to a 30ms sequence, 20ms seek window, and 10ms overlap. This typically results in ~40ms of delay, even if the rest of the system is tuned for minimal latency. Consequently, the lowest achievable latency with all minimal settings was approximately ~80ms.
Nonetheless, TimeStretch still sounds fantastic, so during fast-forwarding or slow motion, PCSX2 will activate TimeStretch until the game returns to normal speed.
During my tests on Linux, with all settings minimized, I experienced an end-to-end audio latency of about 11ms, which is ideal for rhythm-based games! Over several hours of gameplay in Frequency, I encountered just 48 partial underflows, which were unnoticeable to me; however, more sensitive users might want to increase the buffer size.
New Windows Backends
For Windows, I’ve added two new backend modes. Special thanks to @Filoppi for their open PR mozilla/cubeb#740 on cubeb, which greatly facilitated this update.
WASAPI Exclusive Mode: This mode is quite popular, offering high compatibility and very low latency, with the potential to achieve below 3ms, depending on your hardware. The catch is that it lacks mixer support, meaning no volume adjustment and other applications won’t be able to play audio concurrently.
IAudioClient3: This is a more contemporary audio interface from Microsoft. It requires hardware that supports WaveRT to operate in low latency mode. If WaveRT is available, then IAC3 can achieve latency at or below 3ms without the downsides of exclusive mode. If WaveRT isn’t supported, it functions at 10ms latency, similar to WASAPI shared mode. Most hardware produced after 2015 supports WaveRT, making this the preferred option, though older hardware can still utilize WASAPI exclusive mode.
