Add 0RGB1555 pixel format support with NEON optimization #42
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Replace the boolean `downsample` flag with a proper `pixel_format` enum that tracks all three libretro pixel formats. This fixes compatibility with cores that use the legacy 0RGB1555 default format (like mame2003+). Changes: - Add RETRO_PIXEL_FORMAT_0RGB1555 support (was previously rejected) - Rename downsample/buffer to pixel_format/convert_buffer for clarity - Add convert_0rgb1555_neon() processing 8 pixels per iteration - Add convert_0rgb1555_scalar() fallback for non-NEON platforms - Unify conversion dispatch through pixel_convert() function - Reset pixel_format to default when closing cores The 0RGB1555→RGB565 conversion expands green from 5 to 6 bits using g6 = (g << 1) | (g >> 4) for better color accuracy.
There was a problem hiding this comment.
Pull request overview
This PR adds support for the 0RGB1555 pixel format (15-bit color with 1 unused bit) to complement the existing XRGB8888 and RGB565 format support. This change aligns with the libretro specification where 0RGB1555 is the default format if cores don't explicitly set a pixel format, and is used by older arcade cores like mame2003+.
Key changes:
- Refactored pixel format handling from a boolean flag (
downsample) to an enum-based system (pixel_format) supporting three formats - Implemented 0RGB1555 to RGB565 conversion with both NEON-optimized (8 pixels per iteration) and scalar fallback versions
- Improved documentation with detailed explanations of each pixel format, conversion algorithms, and performance characteristics
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Took a look at MyMinUI to learn from the work they've been doing. Main thing that stood out was that we don't support 0RGB1555. We haven't hit specific issues from this yet although we haven't tested all of our new cores thoroughly yet so it'll be nice to already have this in place.