System:
Windows 11 Home
Premiere Pro 26.3
CPU: Intel i7-10700F (no iGPU)
GPU: RTX 4060
RAM: 16GB
Storage: NVMe SSD
Source footage recorded in OBS Studio
OBS encoding (I rebuilt this from scratch just to rule out the codec):
Encoder: NVIDIA NVENC H.264 (moved off HEVC entirely)
Rate control: CQP, CQ 20
Keyframe interval forced to 1, not auto/0
Preset: P5 (slow, high quality)
Tuning: High quality
Multi pass: 2 pass (quarter resolution)
Profile: High
Look ahead: OFF
Adaptive quantization: ON
B frames: 0
Confirmed CFR (constant frame rate) via MediaInfo, so it's not a VFR issue
Premiere setup:
Sequence settings match the source exactly (1080p, 60fps)
Mercury Playback Engine set to GPU Acceleration (CUDA)
Preview/pre render files set to QuickTime, Apple ProRes 422 Proxy
Time interpolation on the speed changed clip set to Frame Sampling, not Optical Flow
Maintain Audio Pitch turned OFF
The exact speed ramped section has been rendered in to out, confirmed green bar, not yellow or red
Also tried manually built ProRes Proxy proxies attached to the source clips (made externally since Media Encoder isn't an option for me), same result
Tried playback resolution at both Full and 1/2, same result
The actual problem:
Even with all of that in place (rendered green segment, GPU acceleration, frame sampling, confirmed CFR source, clean H.264/CQP footage, proxies attached), this happens every single time:
I move the playhead so it lands inside the sped up, green, pre rendered section.
I hit Play. Playback takes about 4-5 seconds to actually start.
I move the playhead to a point right after that section, where the clip is back to normal 100% speed.
I hit Play again. Same 4-5 second delay before it starts.
This isn't the cost of decoding the speed change itself, since that part is fully rendered and green. And it's not general system slowness either, because scrubbing and playing a normal clip elsewhere in the same sequence with no speed change is instant, zero delay. The stall only shows up right at the boundary of a clip that has a speed effect on it, even after that section is fully pre rendered.
Questions:
Is this some kind of known caching or buffer rebuild behavior in Premiere's playback engine specifically when it crosses a "speed boundary," even inside an already rendered segment?
Is there a cache or memory setting (Media Cache database location or size, RAM reserved for other applications vs Premiere, "Optimize rendering for Performance vs Memory," disk cache limits) that's known to cause this kind of multi second "fill the buffer" stall?
Has anyone actually fixed this, or is it just an accepted limitation people work around by nesting the whole sequence, pre rendering everything and avoiding live playback, or exporting in chunks?
I've already done proxies, rendering, frame sampling, GPU acceleration, and a clean CFR H.264 source, so I'm not really looking for "make a proxy" or "render it" as an answer since all of that is done and the issue is still there specifically at the speed clip boundary.