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"Nowadays, video rendering is no longer done with overlays." Darn, I thought this explained why, after upgrading my GPU, videos playing in Chrome have a thin green stripe on their right edge.
The irony is that in 2025, this answer is now wrong again. Starting with smartphones, scanout hardware supports multiple planes/overlays again that are composited on the fly by fixed function blocks. This bypasses having to power on the GPU and wasting memory bandwidth (a large amount of power use in a smartphone). No longer involves hacks with green pixels though.
Right, because we have alpha channels now
The desktop compositors takes the graphics content of all the windows, including their composition visuals, and combines them to form a full desktop image that is sent to the monitor.
...at the cost of latency and efficiency.
This was a nice trick to protect text from copying. For instance, student assignments. Students could still use digital camera on CRT display, but 20 years ago cameras were costly and students did not have them. And typing text from scratch was a tedious job. So online served assignments were not shared too fast.
"Nowadays, video rendering is no longer done with overlays." Darn, I thought this explained why, after upgrading my GPU, videos playing in Chrome have a thin green stripe on their right edge.
MS started exposing some capabilities using MPO in the windows 8 era [0], and they've pretty much always had pretty comprehensive composition pipes in hardware for mobile platforms due to the power/bandwidth limitations meaning compositing the display can be a significant fraction of the total device's performance.
I suspect green (or other block colour) artifacts on video edges are due to bugs/mismatches in specification with the hardware video decoder and how the app displays it, and the bugs that often fall out of that.
Most video compression requires pretty large blocks, normally from 16x16 up 64x64 depending on format, and that may not align with the actual video size (e.g. 1080 does not divide by either). But often implementations still need that extra surface, as things like motion vectors may still refer to data in the "invisible" portion. And it has to be filled with something. It's then real easy to fall into bugs where small numeric errors in things like blending, or even just mix-ups between the different "sizes" that surface has, to cause issues at the edges.
I suspect the other comment about using ANGLE/dx9/dx11-on-12 may be effective as it /also/ causes the hardware video decoder not to be used, which is often a source of "unexpected" differences or limitations that commonly cause errors like that.
[0] https://learn.microsoft.com/en-us/windows-hardware/drivers/d...
This was a nice trick to protect text from copying. For instance, student assignments. Students could still use digital camera on CRT display, but 20 years ago cameras were costly and students did not have them. And typing text from scratch was a tedious job. So online served assignments were not shared too fast.
Around 2005 digital cameras were commonplace. Mobile phones also had cameras by then, even if not very good ones by today's standards. Maybe you're talking about an earlier time?
While cameras were definitely common, they also weren't quiet as ubiquitous as they're today.
Lots of families only had them for trips etc, not readily available for kids to make photos of screens.
Fun Fact: This same sort of thing also happened on the Classic Macintosh Quadra 840AV, when running in 8-bit (256 color) mode. Playback of realtime video capture reserved color index #243 (a very dark green in the system palette), and ANYWHERE that color was used, it would be replaced with the live video. I created some cool effects using this back in the 90s.
Fun Fact: This same sort of thing also happened on the Classic Macintosh Quadra 840AV, when running in 8-bit (256 color) mode. Playback of realtime video capture reserved color index #243 (a very dark green in the system palette), and ANYWHERE that color was used, it would be replaced with the live video. I created some cool effects using this back in the 90s.
Yes, other Mac AV models did the same thing. I remember doing this on the 6100/60AV that we had.
Earlier quoted context omitted.
Around 2005 digital cameras were commonplace. Mobile phones also had cameras by then, even if not very good ones by today's standards. Maybe you're talking about an earlier time?
2005 is pre iPhone. While cameras were definitely common, they also weren't quiet as ubiquitous as they're today. Lots of families only had them for trips etc, not readily available for kids to make photos of screens.