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libretroadmin
0d947c9797
A Color Format core option hands the frontend 30-bit HDR10 or 64-bit scRGB instead of the 24-bit picture, on Vulkan, Direct3D 11 and Direct3D 12 and every renderer of each, through the libretro HDR API (the pixel formats, GET_DISPLAY_METADATA, GET_HDR_METADATA). The picture is placed at the frontend's paper white and mapped onto the display through a Display Transform (beetle-psx's, vendored in rend/hdr/: Reinhard knee by default, which keeps everything below paper white as it was, ACES, ACES 2.0, AgX, PBR Neutral, GT, Hable and others), with optional HDR Expansion. At 24-bit, or when the frontend refuses, none of it runs and the picture is the same to the byte. On Vulkan the encode is the last subpass of the frame's render pass on the rasterizers and one draw on the compute renderer and CPU framebuffers, recorded into the frame's own submission (after the chip's write-out on a frame that has one); on Direct3D 11 and 12 it is one draw in the frame's context or command list, from one shared DXBC blob (tools/rend/kernels_dxbc.sh update-hdr). Nothing is copied and no submission or wait is added. ACES 2.0 (Full)'s cube is baked off the frame by a worker thread handed its jobs through atomics and an eventcount, without locks. tools/vulkan/vk_hdr.sh runs every Vulkan renderer at each Color Format and judges the pictures; tools/hdr/d3d_hdr.sh does the same with the Windows build on Direct3D 11 under wine; tools/vulkan/hdr_hlsl.sh and tools/hdr/hdr_d3d.sh hold the HLSL, and the Direct3D 11 and 12 encoders under wine, to the GLSL over every curve and setting; tools/hdr/hdr_cube.sh holds the worker's cube to the cube baked in place, under TSan and ASan/UBSan. All of them run in the Vulkan negotiation workflow.
163 lines
7.4 KiB
Markdown
163 lines
7.4 KiB
Markdown
parallel-dc
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===========
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parallel-dc is a Sega Dreamcast, NAOMI, NAOMI 2 and Atomiswave emulator
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core for [libretro](https://www.libretro.com) frontends such as
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[RetroArch](https://github.com/libretro/RetroArch).
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It started life as libretro's own fork of Flycast (itself a fork of
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reicast) and has since been developed independently. It is actively
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maintained and is no longer deprecated: much of the emulator has been
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audited against upstream [Flycast](https://github.com/flyinghead/flycast)
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and other references, the useful upstream fixes were brought over after
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being verified, and a great deal has been added or rewritten that
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upstream does not have.
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The same goals apply throughout the code base:
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- **Accuracy** - emulate what the hardware does, not what one game needs.
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- **Performance** - every change has to be at least as fast as what it
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replaces, and is measured. No allocation, shader compilation or blocking
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wait in the middle of a game.
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- **No locks** - threads talk through lock-free queues and atomics
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(libretro-common's `retro_atomic`), never mutexes or sleeps.
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- **Portability** - plain C/C89 where possible, built for every libretro
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platform, with libretro-common used for threads, file I/O and archives.
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What it runs
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------------
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- **Dreamcast** discs: CHD, GDI, CUE/BIN, CDI, and ELF programs, plus
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M3U playlists for multi-disc games.
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- **NAOMI**, **NAOMI 2** and **Atomiswave** games, as MAME romsets or
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flat `.bin`/`.dat` images. A romset is recognised by its contents, not
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its file name, so non-MAME sets work too, and a game can be started out
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of a merged set (a core option picks which one).
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- Any of the above inside **zip, 7z or rar** archives (RAR 2.9 to 5).
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Large compressed disc tracks are read as they are needed instead of
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being unpacked into memory first.
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- **No BIOS required.** The Dreamcast and NAOMI BIOS routines are
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reimplemented (HLE), including the NAOMI test menu. With
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*Use Real BIOS (If Available)* on (the default), a real BIOS in the
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system directory is used when present.
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What is different from upstream Flycast
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---------------------------------------
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### Video
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- **A renderer for every frontend driver**: OpenGL / OpenGL ES, Vulkan,
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Direct3D 9, Direct3D 11 and Direct3D 12. The core uses whichever the
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frontend prefers.
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- **Per-pixel translucency sorting** (order-independent transparency) on
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OpenGL 4.3+, Vulkan, Direct3D 11 and Direct3D 12, chosen with a core
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option rather than a build flag. Frames with more translucent pixels
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than the buffers hold are drawn in bands instead of losing pixels.
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- **Compute renderer** (Vulkan, experimental, *Rendering Method* option):
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draws the screen tile by tile with compute shaders the way the PowerVR2
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does, with exact per-pixel sorting. The rasterizer remains the default.
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- **TA processing on the GPU** (*TA Processing* option, Vulkan and
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OpenGL 4.3+): the display lists the game sends are turned into vertices
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on the GPU, byte-identical to the CPU path.
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- **SSAA** (2x/4x/8x, Vulkan), sized to the video memory the driver
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reports.
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- **Texture decoding on the GPU**, with textures written straight into an
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upload ring (no staging copy per texture). Shaders and pipelines are
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built at start-up and cached on disk, so there are no mid-game compile
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hitches.
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- **Render-to-texture** kept on the GPU and copied back to emulated video
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memory only when the game actually reads it; the per-game RTT setting
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is gone.
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- PowerVR features are always on, as on hardware: fog, modifier volumes
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(shadows, including in the per-triangle renderers) and mipmapping.
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*Force Texture LOD0* replaces the old mipmapping switch.
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- Fog, shadows, depth, palettes, texture formats and clipping audited and
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fixed against the hardware; host-side precision loss in shaders and
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colour conversion removed. glm replaced by a small C89 matrix header.
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- Vulkan memory handled by a lean C89 block heap instead of the Vulkan
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Memory Allocator, sized from the driver's real memory budget.
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- Threaded rendering reworked: one emulated frame per `retro_run`, no
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skipped frames, output identical to non-threaded rendering.
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- **HDR output** (*Color Format*: 30-bit HDR10 or 64-bit scRGB; Vulkan,
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Direct3D 11 and Direct3D 12): the picture is placed at the frontend's
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paper white and mapped onto the display through a selectable *Display
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Transform* (Reinhard soft knee by default, which leaves everything below
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paper white as the 24-bit picture; ACES, ACES 2.0, AgX, Khronos PBR
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Neutral, GT, Hable and others), with optional *HDR Expansion* into the
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headroom. The 24-bit output is unchanged, to the byte, and is what a
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frontend that cannot present HDR gets.
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### CPU and timing
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- **SH4**: instruction fixes from an audit against upstream and the
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hardware (DIV1, FTRC, FIPR/FTRV and more); every instruction now has a
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recompiled form; faster x86-64 and ARM64 recompilers (direct block
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links, loads/stores through the host memory mapping, fewer instructions
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per access); and an optional cycle-accurate timing model
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(*SH4 Timing*: Legacy / Accurate; NAOMI 2 always uses Accurate).
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- **MMU** (Windows CE games): supported by the 32-bit ARM recompiler as
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well, with translation tables on every host, correct TLB invalidation,
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write protection and self-modifying-code handling.
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- **ARM7 recompiler** for x86-64 (*Sound CPU Recompiler* option), with an
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interpreter fallback.
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- Scanline and frame timing fixed so frames come out at the right rate
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without lost lines.
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### NAOMI 2
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- The ELAN geometry processor is emulated in C89, with SIMD (SSE2/NEON)
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vertex lighting and its memory mapped for the recompilers.
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- 45 NAOMI 2 games in the game table, with input maps; romsets and
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cartridge sets start without a BIOS.
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### Sound
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- AICA audited: two-pole low-pass filter, 20-bit interpolation, faster
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channel loop, save states that keep pending notes and CD audio.
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- The DSP is always emulated. Each video frame carries exactly the number
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of samples the hardware produces for it, not fixed-size chunks.
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### Frontend and I/O
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- Lock-free threading throughout: emulation thread, CHD read-ahead,
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modem / broadband adapter / NAOMI network, save writer, archive
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decoding. No C++11 threads, `<mutex>` or `<chrono>`.
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- File I/O goes through the frontend's VFS and libretro-common, with
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sectors read in place rather than copied and archives decoded in the
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background.
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- Obsolete core options removed (Framerate, Fog Effects, Volume Modifier,
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Enable DSP, Enable RTT Buffer, the OSD/FPS options and others): the
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hardware behaviour they switched off is now always emulated.
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Building
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--------
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```
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make -j$(nproc)
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```
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Use `platform=<name>` for other targets (for example `platform=win`,
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`platform=libnx`, `platform=emscripten`; see the Makefile). The core is
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built as `parallel_dc_libretro`, and its options keep the `reicast_` prefix so
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existing configurations still apply.
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Tests
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-----
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`tools/` holds the regression tests used during development: a headless
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runner and test disc (`tools/threads`), and checks for the SH4 and ARM7
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recompilers, AICA/DSP, the NAOMI 2 geometry chip, the tile accelerator on
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CPU and GPU, the texture decoders on every API, a reference software
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renderer used as an oracle (`tools/rend/refsw`), the Vulkan heap, and the
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CHD and archive readers.
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License
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-------
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GPL version 2; see [LICENSE](LICENSE).
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All code contributed to this fork is *not* bound by the Individual
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Contributor License Agreement of the reicast repository
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(https://github.com/reicast/reicast-emulator) and shall *not* be
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considered a contribution to that repository.
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