Well, I’ve gotten further in this particular stab at rewriting the subtitle rendering routine than I ever have before. The main sticking point seems to be that there’s a Windows-specific bug in ImageMagick+Pango, which means even if everything else is perfect (and we’re not quite there yet either), we’ll need to maintain two different rendering engines, which produce slightly different results, which is relevant in the sense that the SRT timings are optimized for the Windows method (the new method can occasionally be one frame off), etc, etc.
And, well, the script is slow as molasses. But it’s slow across all platforms, so there’s that.
Two steps forward, one step back. The newest ImageMagick fixes the ImageMagick+Pango text rendering bug, so we now have cross-platform parity. Unfortunately the newest ImageMagick also completely changes a few critical functions so all the scripts that worked previously are now broken to some degree. But equally broken across all platforms… I guess this will be good practice for the Perl 6 apocalypse.