marqs85
commented
3 years ago I understand the issue as my Panasonic EZ950 behaves in a similar way (never had the issue with older VT30 plasma, though). However, OSSC has inherent limitation of input sampling rate being coupled to output total width. A few tricks can be done in certain cases (like line3x generic 4:3), but in general you don't have much control over active width if you aim for best compatibility.
For example, let's consider 1440x480 which is probably the likeliest "high-res" 480p mode these devices would accept. Sampling rate would be 2x858=1716 which would have active content on roughly 0.75x1716=1287 pixels. To maintain correct aspect, you'd need to scale that 1287px into pillarboxed area of 1440, i.e. 1080 pixels. It could be possible to do that via nearest neighbor or even linear horizontal scaling on the FPGA, but it'd be a tradeoff in quality.
The upcoming Pro model gets a way with this limitation by decoupling sampling and output. There you can just select suitable sampling rate for target output width which is then scanned out using a different clock.
wolf-re
The idea is to actually produce a 16:9 output image from a 480p (576p) input by padding it with black pixels left and right.
In the 1x (pass-through) mode this should be 854x480 (1024x576) where the 720 / 640 active pixels are sampled to the middle of the buffer. Then the full buffer width is output to yield an actual 16:9 image. This could also work for a 2x mode, with the current line buffer of 2048 pixels giving 1708x960 (2048x1152).
So if I'm not mistaken this would work nicely for 1:1 pixel aspect ratio cases, like (Dreamcast) 640x480 VGA input. For the non-1:1 cases this would require either undersampling or a slightly wrong AR in the boxed output. However when using the 2x upscale, I believe the OSSC can do the 2x pixels by increasing the ADC sample rate. In this case the non-1:1 AR case would not be undersampled any more and still give a correct AR in the output.
Why would this make sense? Well there seem to be some new-ish TVs (e.g. the Panasonic TX-50EXW784) and receivers (e.g. the Marantz SR6008) which cannot switch aspect ratio in game mode. So everything you blast at them is always displayed in 16:9 regardless of what the source says it should be. This even goes for VGA type input, which makes absolutely no sens as this is clearly 1:1 pixel AR content, but that's what they do. With this feature we could nicely work around such displays.
Would such a signal be anything even remotely spec conform?
Could this be achieved with the current state by creatively using the "Advanced timing tweaker" and "post proc." features?
ps.: I'm volunteering as a tester :smile: I do have the above mentioned two devices and also a much more compatible desktop monitor.