The documented way to grab a reliable composited frame at timeline time t is to render a very short range starting at t with /render-onserver and then capture its first frame. In practice the first frames of a range render come back with image and video layers missing.
I rendered several 0.06s ranges (rangeStart t, rangeEnd t+0.06, so 2 frames) over a project whose grid layer holds seven JPEG members. Every render succeeded and produced a valid file, but every image cell was solid black. Synthetic layers on the same frames – text, shapes, the label bar – rendered correctly, so the composite itself was fine; only the media had not loaded.
Re-rendering the same timeline region as a 1.4s range and pulling a frame about 1s in showed all seven images correctly. Nothing about the project changed between the two renders. So the media is fine; the export simply starts before it is ready.
This cost me a diagnostic cycle: I concluded the images were broken and started replacing them, when the only problem was the length of the range.
Two requests:
1. Apply the same warm-up treatment that v8.7.46 gave 3D models to ordinary image and video layers, so the first frame of a range render is trustworthy.
2. Related and arguably worse: because a 2-frame range can never reach the "3 consecutive frames failed to render" threshold, a short range render SUCCEEDS on a project containing a clip that cannot be decoded at all. It writes a valid file full of blank frames. A short range render therefore cannot be used to verify that media decodes – and there is no signal that anything went wrong.
Steps to reproduce
1. Build a project with image or video layers that begin after t=0.
2. POST /render-onserver (or /render-onserver-job) with rangeStart t, rangeEnd t+0.06, fps 30.
3. Capture the first frame of the returned clip.
4. Repeat with rangeEnd t+1.4 and sample about 1s in.
Expected
The first frame of a range render is fully composited, including image and video layers.
Actual
Short-range renders return frames with image/video layers missing (solid black in the grid cells) while text and shape layers composite correctly. A longer range renders the same moment correctly.
Context
Video Editor headless render, /render-onserver and /render-onserver-job with rangeStart/rangeEnd. Board id New_Pixelgbra_Website. Project 1080×1920, 30fps, grid layer with 7 JPEG members.
Environment
App version: 8.8.0
Platform: Windows 11 (AMD64)
