OBS Settings for Capture Cards: Video, Audio Routing and Lip Sync

If you use a capture card to turn a DSLR or mirrorless camera into a webcam, OBS needs to know two things: what video format the camera is sending, and where your voice should come from. Most capture card problems in OBS come from getting one of those wrong, not from a hidden setting.

The short answer

No single set of OBS settings is best for every capture card. The settings that work are the ones that match your camera's HDMI output, send exactly one speech source to the mixer, and keep that speech in sync with the picture. The menu names below are the ones OBS uses. The options you see depend on your operating system, your OBS version and your capture card's driver, so check your card's documentation where it differs.

• Set the capture source's resolution and frame rate to match what the camera actually outputs over HDMI.
• Set the OBS canvas and output frame rate to match, or to a rate that divides evenly from it.
• Decide whether your voice arrives through the camera's HDMI audio or through a separate microphone, then mute the other path.
• If the microphone connects to the computer separately, delay it with Sync Offset so speech lines up with lip movement.
• Match the OBS sample rate to your audio devices and keep monitoring off unless you are using headphones.
• If you send OBS video into a call through Virtual Camera, set up audio separately, because Virtual Camera carries video only.

Video settings that affect the picture

Add the card as a Video Capture Device source. On Linux this is listed as Video Capture Device (V4L2). In its properties, change Resolution/FPS Type from Device Default to Custom. Then pick the resolution and frame rate your camera sends over HDMI. Leaving it on Device Default can produce a resolution or frame rate that doesn't match the incoming signal, which can cause stutter or a soft image.

Under Settings, then Video, set the base canvas and output resolution to match your target. Set the common FPS value to the camera's frame rate where possible. When the output frame rate doesn't divide evenly into the source rate, motion can judder, and that judder can make lip movement look slightly off even when the audio is correctly timed.

The camera must send a clean HDMI signal, meaning one without on-screen menus, focus points or recording indicators. Whether a camera can do this, and at which resolutions and frame rates, depends on the model. Check this before changing anything in OBS, because no OBS setting can remove overlays the camera adds.

Getting capture card audio into OBS

HDMI can carry audio as well as video, so a capture card may deliver the camera's sound along with the picture. Depending on the card and platform, that audio either appears inside the video source or shows up as a separate audio input device.

On Windows, the Video Capture Device properties include Audio Output Mode. Choose Capture audio only if you want the card's audio to appear in the OBS mixer, where you can meter it, filter it and adjust its sync. The desktop audio options instead send the sound to your system output, which can stop it from being controlled the same way inside OBS. If the card shows its audio as a separate device, enable Use custom audio device and select that device. On other platforms, or with other cards, you may need to add the card's audio as its own Audio Input Capture source.

Choosing which microphone carries your voice

With a camera-and-capture-card setup, your voice can reach OBS in three ways. Each one trades convenience against speech quality and sync.

Route | How it reaches OBS | Sync with video | Speech-quality notes

Camera's built-in mic | Embedded in HDMI through the capture card | Usually travels with the picture | The mic is often far from the mouth, so it picks up more room sound and camera handling noise

External mic plugged into the camera | Embedded in HDMI through the capture card | Usually travels with the picture | Placement can be much better; quality depends on the camera's audio input and level control

USB or interface mic on the computer | Separate audio input in OBS | Often arrives earlier than the video | Usually the most control over placement and gain, but typically needs a sync offset

Whichever route you pick, mute or remove the others in the mixer. If the camera mic and a USB mic are both live, your voice is captured twice with a small time difference between them. That can sound hollow or echoey.

Fixing lip sync

The camera's processing and the capture card both add delay to the video. A microphone connected directly to the computer skips that path, so your voice can be heard slightly before your lips move. OBS handles this with Sync Offset, found in Advanced Audio Properties, which delays an audio source by a set number of milliseconds. The right value depends on the camera, the card and the frame rate, so there is no universal number. Measure it for your own setup.

• Open Advanced Audio Properties from the audio mixer.
• Make a short test recording in which you clap sharply in view of the camera.
• Play it back frame by frame and compare the moment the hands meet with the start of the clap sound.
• If the sound comes first, raise the microphone's Sync Offset and record again.
• Repeat until the sound and the visible clap line up, then recheck whenever you change resolution, frame rate or hardware.

Audio settings that matter for speech

• Sample rate: under Settings, then Audio, set the sample rate to match your microphone and capture card where possible. A mismatch forces resampling and has been linked to crackling or drift.
• Monitoring: leave Audio Monitoring off for your voice source unless you are wearing headphones. Monitoring through speakers can feed back into the microphone.
• Levels: watch the mixer meter while speaking normally. Speech should sit well below the top of the meter, and loud peaks shouldn't reach the red zone, where clipping causes distortion that can't be removed later.
• Filters: OBS includes Noise Suppression, Noise Gate, Compressor and Limiter filters. Apply them only to the voice source. Use them sparingly, because heavy noise suppression or a tight gate can clip the starts and ends of words.
• Gain: set level at the source first, on the camera's audio input or the microphone interface, and use OBS gain only for small corrections. Boosting a weak signal also raises the background noise.

Using the setup in video calls

OBS Virtual Camera passes video to conferencing apps but not audio. In the call app, you will usually select your microphone directly as the audio input. That means OBS filters and the Sync Offset you set no longer apply, and the call may show the same audio-ahead-of-video offset described above. To send OBS-processed audio into a call, you need a separate virtual audio device, which OBS does not provide on every platform.

Common problems and checks

• Black or frozen image: confirm the camera is sending HDMI output, that its own screen or menus aren't taking over the output, and that no other app is using the capture card.
• No audio from the card: check Audio Output Mode and the custom audio device setting, or add the card's audio as a separate input.
• Audio drifts out of sync over time: check that sample rates match across devices, then repeat the clap test.
• Voice sounds doubled or hollow: two sources are capturing the same speech, so mute one.
• Card missing in OBS: some cards need the manufacturer's driver or utility. Check its documentation for your operating system.

Limits of this guide

This guide describes standard OBS controls and general audio principles. It isn't based on testing specific capture cards or cameras. No verified measurements were available for latency, required sync offsets, supported formats for particular models, or the speech quality of camera microphones versus separate ones. Those details vary by hardware and software version, so confirm them with your capture card and camera documentation and with your own test recordings.