OBS "Starting the Output Failed" - Fix

OBS "Starting the Output Failed": Fix

You click Start Streaming, and OBS returns a dialog reading Starting the output failed. Please check the log for details. Nothing starts. The dialog usually adds a line suggesting you update your video drivers if you are using the NVENC or AMD encoders.

That suggestion is a guess on OBS's part, and it is right perhaps a third of the time. The accurate description of what happened is narrower: OBS asked an encoder to initialise, and the encoder refused. Your scenes are fine. Your sources are fine. Your audio is fine. One component failed to start, and the reason it failed was written to a log file half a second before the dialog appeared.

That log is the fastest route to the answer, and almost nobody opens it. This guide starts there.

Recording, not streaming? If the dialog appeared when you clicked Start Recording rather than Start Streaming, and the wording you saw was closer to An error occurred while starting the output, the causes are different enough to be a separate problem. OBS "An Error Occurred While Starting the Output": Fix covers the recording side: output paths, container limits and audio track mismatches.

Step 1: Read the Log Line That Names Your Cause

OBS writes a timestamped log for every session, and the failure appears in the last few lines.

1. In the OBS menu bar, open Help > Log Files > Show Log Files, or View Current Log to open it directly.
2. Open the most recent file and scroll to the bottom.
3. Read the last ten to fifteen lines before the session ended.

You are looking for a line beginning with [obs-nvenc], [FFmpeg, [x264, or [amf, or containing the phrase Failed to start. That line names the encoder that failed and, usually, why.

Common lines and what they mean:

If you would rather not interpret it yourself, upload the log with Help > Log Files > Upload Current Log File. It produces a link to OBS's own log analyser, which flags the failing line in plain language.

Step 2: Confirm the Selected Encoder Still Exists

The single most common cause is an encoder selection that no longer matches the hardware present.

This happens more often than it sounds. A settings profile copied from another machine, a graphics card swapped out, a laptop that boots on integrated graphics, or an OBS update that renamed encoder entries will all leave you with a profile pointing at an encoder that is not there. OBS keeps the stale selection, shows it in the dropdown, and only discovers the problem when you press start.

1. Open Settings > Output.
2. Set Output Mode to Advanced so every encoder option is visible.
3. Open the Streaming tab and look at Video Encoder.
4. Change it to Software (x264) and click Apply.
5. Try again.

If it starts, the encoder selection was the fault. x264 runs on the CPU and exists on every machine, which is exactly why it is the right diagnostic: it removes the GPU from the equation entirely.

Do not leave it there permanently if you have a capable GPU. x264 will start competing with whatever else your processor is doing, and on a machine that is also running a game you will feel it. Work through the remaining steps, then set the encoder back to your hardware option.

On the encoder names: on NVIDIA cards choose NVIDIA NVENC H.264, on AMD choose AMD HW H.264 (AVC), on Intel choose QuickSync H.264. If your dropdown lists an HEVC or AV1 variant, those are newer and narrower in support; H.264 is the option to test with.

Step 3: Turn Off Hardware-Accelerated GPU Scheduling

If x264 starts cleanly but your hardware encoder still fails, the next suspect is a Windows feature rather than OBS.

Hardware-accelerated GPU scheduling (HAGS) hands GPU work queue management from the driver to the GPU itself. It is a reasonable feature that has a long history of interfering with hardware encode paths, and it is enabled by default on many systems. The classic signature is this error appearing suddenly after a Windows feature update, with nothing changed on your end.

1. Press the Windows key, type Graphics settings, and press Enter.
2. Open Change default graphics settings.
3. Turn Hardware-accelerated GPU scheduling off.
4. Restart the machine. The toggle does nothing until you do.

Retry with your hardware encoder selected. If it now starts, HAGS was the cause and leaving it off costs you nothing measurable for recording or streaming work.

Step 4: Free Up Contended GPU and Encoder Resources

Encoder initialisation needs memory and, on the GPU path, an available encode session. If something else has already taken what OBS needs, initialisation fails.

Work through these in order, testing after each:

Close other capture software. NVIDIA App instant replay, ShadowPlay, AMD ReLive, Xbox Game Bar background recording, Discord's Go Live, and any other running instance of OBS all hold encoder sessions. Quit them properly rather than minimising them.

Turn off browser hardware acceleration if a browser is open. Chrome and Edge with many tabs will hold GPU resources. In the browser settings, search for hardware acceleration and disable it, then restart the browser.

Start OBS before the game, not after. A game that has already claimed the GPU at exclusive fullscreen leaves OBS fighting for what remains. Launch OBS first, then the game, and set the game to borderless windowed rather than exclusive fullscreen.

Run OBS as administrator. Right-click the shortcut and choose Run as administrator. This raises OBS's priority for resource requests against elevated processes and anti-cheat drivers that would otherwise refuse it. To make it permanent: right-click the shortcut, Properties > Advanced, tick Run as administrator.

Step 5: Clean Install the Graphics Driver

If the log named a driver-level failure, or if steps 2 to 4 changed nothing, the driver install is the remaining candidate. A routine driver update layers a new install over the old one and carries corrupted encoder profiles forward with it, which is why "I already updated my drivers" is not the same as having fixed this.

1. Download the current driver for your exact card model from nvidia.com, amd.com, or intel.com. Do not use Windows Update or a driver utility for this.
2. Run the installer and choose Custom (Advanced) rather than Express.
3. Tick Perform a clean installation. This wipes existing profiles and settings before writing new ones.
4. Restart, reopen OBS, and set the encoder back to your hardware option.

Expect the screen to flicker or go black briefly during the install; that is normal. If a clean install still fails, use the manufacturer's older branch driver from a few releases back. New driver branches do occasionally ship with broken encode paths, and rolling back is a legitimate fix rather than a workaround.

Symptom Router

The Underlying Trade

Every step above exists because OBS gives you direct control of the encoder. That control is genuinely valuable when you are running a multi-camera broadcast and need to pin a specific bitrate to a specific hardware path. It is the reason OBS is the tool of record for live production.

It is also the reason a settings profile can point at an encoder that no longer exists, and only tell you at the moment you press start.

If what you actually do is record software tutorials and product walkthroughs, you are paying the maintenance cost of a broadcast desk for a job that never involves one. Cubix Capture has no encoder dropdown to get wrong. It selects the capture path itself, on Windows and Mac, and applies the zoom and cursor smoothing during capture so the file is finished when you stop. The free Starter plan runs without an account, which is enough to check the output against your own material.

Keep Reading

• OBS "An Error Occurred While Starting the Output": Fix for the recording-side variant of this dialog.
• OBS NVENC Error: How to Fix NVIDIA Encoding Issues if the log named NVENC.
• OBS Encoding Overloaded Error: How to Fix if the output starts but cannot keep up.
• OBS Best Settings for Screen Recording for a configuration baseline to rebuild from.