The RetroTink 4K received a significant update via Experimental Firmware Version 1.5.1 which adds some interesting features for downscaling:
- Menu now works in 240p output using temporal downscaling
- Added ability to generate interlaced output timings
A custom modeline is required for interlaced output, where the vertical active size is the sum of both fields, and interlaced is defined by adding ‘1’ as the last comma separated item in the text file. I tested the 480i modeline that was listed with the firmware announcement on the RetroTink’s official discord server:
720, 16, 62, 138, 0, 480, 4, 3, 22, 0, 59.94, “720x480i59.94”, 1
Scaling does not currently work with interlacing, so a 480i output can only come from a 480p/i input, 720i from 720p/i and so on. 480i resolution passthrough is not without lag (I measured up to 36msec with the Time Sleuth), Edit: 36msec lag is only in triple buffer mode. With Gen Lock in the HDMI Output settings, lag in all downscaling scenarios should only be approximately 3msec. Currently, the interlaced output is effected by the deinterlacing menu settings, where the Blend, Weave, Linear and LCD options all produced an equivalent crisp and clean 480i output.
This is a significant iteration for anyone wanting to interlace a progressive input resolution, transcoding, or wanting to use the RetroTink 4K’s filtering options in signal passthrough. Keep in mind that my testing did not go beyond 15KHz output and that this version is an experimental firmware and some kinks may still need ironing out. If you are already downscaling with the RetroTink 4K then this update is essential for the 240p menu fix alone.