Video stutters or drops frames
The output is technically running but visibly hitching — frames repeated, audio out of sync, encoder errors in the log.
First, look at the Performance panel in Desktop (or the Performance Report under Runtime) for the per-tick processing time. If processing time is regularly ≥ 80% of frame budget, the host is over-committed.
Common causes (in order of probability):
- GPU clock not locked. The GPU's idle-vs-load power state ramp takes 100s of milliseconds — long enough to drop frames at 60 fps. Lock clocks via Composer's settings or
nvidia-smi -lgc <min>,<max>. See Tuning. - Hardware-accelerated GPU scheduling is on (Windows 11). NVENC sessions occasionally drop frames with this enabled. Disable it under Settings → System → Display → Graphics → Default graphics settings and reboot. Walkthrough in Performance and optimization.
- Capture card on a narrow PCIe slot. Verify with
nvidia-smi -q | grep -i pcie(or your motherboard's diagnostic) that the slot is x4 or wider. x1 / x2 slots throttle high-bitrate capture. - Hyper-V enabled. The Hyper-V hypervisor adds GPU-virtualisation overhead that costs measurable frame budget. Disable Hyper-V in BIOS / Windows Features.
- Frame-rate mismatch. A 60 fps project ingesting 30 fps clips spends extra CPU on frame doubling. Pre-convert source media to the project frame rate.
- Resolution scaling at runtime. A scene rendering at UHD with HD source clips spends frame budget upscaling. Pre-rescale media files to the project resolution.
- NVENC saturated. Too many concurrent encoders. Reduce target count, or move heavy encoders to libx264 (CPU) on a host with CPU headroom.
- Sharing the GPU with the desktop compositor. On a single-GPU Windows host, the desktop compositor competes with Composer. Use the CPU's integrated graphics for the desktop, or fit a second cheap GPU. Enabling the screen saver also helps (suspends the desktop compositor after inactivity).
- Remote-access tools running. TeamViewer, RDP, AnyDesk etc. periodically grab framebuffers. Don't run them during a live show.
The full performance recipe is in Tuning for maximum performance and Performance and optimization.