04-28-2023, 10:22 AM
When presenting audio in an Experiment Builder task on Windows, you have two options for playback drivers: DirectX and ASIO. For any experiment that requires precise synchronization between audio events and eye-tracking data, ASIO is the optimal choice.
ASIO (Audio Stream Input/Output)
ASIO is a protocol designed for low-latency, high-precision audio which allows Experiment Builder to communicate directly with the sound card.
It's important to be aware of emulated ASIO drivers like ASIO4ALL. These drivers act as a "middleman," tricking software into recognizing a non-ASIO device as compatible.
The timing of these intermediate drivers is typically very poor and will not provide the low-latency performance expected of a true ASIO device. These drivers should be avoided, as you will not get the timing or reliability required for precise research.
DirectX Audio
DirectX audio works well for most use cases where precise timing is not critical, such as playing feedback sounds or verbal instructions.
ASIO (Audio Stream Input/Output)
ASIO is a protocol designed for low-latency, high-precision audio which allows Experiment Builder to communicate directly with the sound card.
- How it Works: By bypassing the standard Windows audio system, Experiment Builder can schedule audio playback with high precision, ensuring the sound plays at the exact time requested.
- Performance: ASIO provides millisecond-accurate playback and recording with latencies of less than 3 ms. This facilitates easy and accurate alignment with the gaze data.
- Compatibility: ASIO is not supported on all sound cards. You can find a list of supported and verified sound cards in the Experiment Builder Manual (Help Menu -> Installation -> Windows PC Installation -> ASIO Card Installation). If you have questions about a specific card, please contact support@sr-research.com.
It's important to be aware of emulated ASIO drivers like ASIO4ALL. These drivers act as a "middleman," tricking software into recognizing a non-ASIO device as compatible.
The timing of these intermediate drivers is typically very poor and will not provide the low-latency performance expected of a true ASIO device. These drivers should be avoided, as you will not get the timing or reliability required for precise research.
DirectX Audio
DirectX audio works well for most use cases where precise timing is not critical, such as playing feedback sounds or verbal instructions.
- How it Works: When a sound is triggered, the audio buffer is handed off to the Windows DirectX system, which then schedules the playback. This indirect process introduces a delay.
- Performance: This can result in latencies of 7-200 ms with high variability. This uncertainty makes it difficult, if not impossible, to align the audio playback precisely with the gaze data.
- Compatibility: DirectX is supported on all sound devices.