Document the hardsub/auto-split fork

Add FORK_NOTES.md describing the new features, a README pointer, and keep
the known-good baseline encoder as contrib/dvd-safe-converter.sh (the
reference the Compatibility profile is modelled on).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

FORK_NOTES.md

@@ -0,0 +1,66 @@
+# DeVeDe-NG — Hardsub & Auto-split Fork
+
+This is a fork of [DeVeDe-NG](https://gitlab.com/rastersoft/devedeng) that adds
+three things aimed at producing burn-ready NTSC DVDs from arbitrary video files:
+
+1. **Embedded subtitle detection + hardsubbing (burn-in).**
+2. **Selectable DVD encode profiles** (Compatibility / High quality / Custom).
+3. **Automatic splitting of over-long projects across multiple ISOs / DVD-Rs.**
+
+The baseline encode is modelled on the known-good script in
+[`contrib/dvd-safe-converter.sh`](contrib/dvd-safe-converter.sh).
+
+## 1. Hardsubbing embedded subtitles
+
+The analyzer (`ffprobe` / `avprobe`) now detects embedded subtitle tracks and
+classifies each as **text** (SubRip/ASS/mov_text/WebVTT) or **image**
+(PGS/VOBSUB/DVD subtitle). In a movie's *Subtitles* properties page a
+**"Burn in embedded subtitle"** dropdown lets you pick one track to render
+permanently into the picture.
+
+- **Text** subs are burned with ffmpeg's `subtitles=` (libass) filter, applied
+  after scaling to the DVD size.
+- **Image** subs are composited with an `overlay` filtergraph *before* scaling,
+  so bitmap positioning stays aligned with the source frame. (OCR-to-text is an
+  optional future enhancement; the default overlays the bitmap directly.)
+
+Burned-in subtitles are part of the video; the existing *soft* subtitle support
+(spumux subpicture streams from external files) is unchanged.
+
+## 2. Encode profiles
+
+A project-level **Encode profile** selector (next to the disc-size control,
+DVD only):
+
+| Profile | Video | Audio | Notes |
+| --- | --- | --- | --- |
+| **Compatibility (4500k)** | CBR 4500k | AC3 192k | Old-player safe baseline (~133 min / single-layer disc). |
+| **High quality (fill disc)** | VBR, fills disc | AC3 448k | Best quality per disc. |
+| **Custom** | user kbps | user kbps | Advanced; clamped to stay within DVD spec. |
+
+NTSC DVD audio is AC3 for all profiles (the upstream default was MP2 for NTSC),
+matching the baseline script and maximising player compatibility.
+
+## 3. Splitting long projects across discs
+
+Usable disc capacity is taken from the selected disc size (with the existing
+~10% safety margin). When a project does not fit on one disc at the chosen
+quality, you are asked whether to:
+
+- **Split into N discs** — keep the quality and author one DVD/ISO per disc
+  (`name-disc1.iso`, `name-disc2.iso`, …), **or**
+- **Reduce bitrate** — squeeze everything onto a single disc (the original
+  behaviour).
+
+Multiple titles are distributed across discs whole. A single movie that is
+itself larger than one disc is split by time at the **chapter boundary nearest**
+each disc's capacity (falling back to an even time cut when the movie has no
+chapters). Split discs are authored without a menu — each disc plays its
+segment(s) directly.
+
+### Limitations
+
+- Split discs have no DVD menu.
+- Burning is per-disc: the app produces the ISOs; burn each in turn.
+- Image-subtitle burn-in is supported by the ffmpeg backend; the avconv backend
+  handles text subtitles only.