Problem
USB microphone audio is delayed relative to HDMI camera audio, creating an audible lip-sync problem.
Solution
Root Cause / Diagnostic:
Hardware HDMI capture cards introduce substantial frame-buffering, de-interlacing, and color-space conversion latency (typically between 60ms and 180ms) before delivering video frames to the compositor. Conversely, USB audio interfaces bypass video processing pipelines and deliver audio packets nearly instantaneously, causing spoken audio to lead the camera visual.
Actionable Fix:
1. Measure the exact offset and apply an Audio Delay buffer (typically between +80ms to +150ms) to the USB microphone source within the encoder's Advanced Audio Properties (OBS: Sync Offset; vMix: Audio Delay).
2. Route the primary camera through a low-latency capture pipeline (PCIe capture card instead of USB 2.0 dongle) and lock hardware buffering to "Disabled" in device properties to minimize baseline video latency.
3. Record a physical hand-clap or visual flash slate directly on camera; inspect the recorded timeline waveforms in a video editor to verify audio and video transients align within ±5 milliseconds.
Pro Tip:
If your camera body features a 3.5mm mic input with clean preamps, route the analog mixer output directly into the camera; this embeds audio onto the HDMI carrier, guaranteeing hardware-level lip-sync across all capture devices.
Hardware HDMI capture cards introduce substantial frame-buffering, de-interlacing, and color-space conversion latency (typically between 60ms and 180ms) before delivering video frames to the compositor. Conversely, USB audio interfaces bypass video processing pipelines and deliver audio packets nearly instantaneously, causing spoken audio to lead the camera visual.
Actionable Fix:
1. Measure the exact offset and apply an Audio Delay buffer (typically between +80ms to +150ms) to the USB microphone source within the encoder's Advanced Audio Properties (OBS: Sync Offset; vMix: Audio Delay).
2. Route the primary camera through a low-latency capture pipeline (PCIe capture card instead of USB 2.0 dongle) and lock hardware buffering to "Disabled" in device properties to minimize baseline video latency.
3. Record a physical hand-clap or visual flash slate directly on camera; inspect the recorded timeline waveforms in a video editor to verify audio and video transients align within ±5 milliseconds.
Pro Tip:
If your camera body features a 3.5mm mic input with clean preamps, route the analog mixer output directly into the camera; this embeds audio onto the HDMI carrier, guaranteeing hardware-level lip-sync across all capture devices.