libretro/wiki/advanced-usage.md

Advanced Usage

Fine-grained control over pack generation, hardware filtering, truth analysis, and verification.

Custom Packs

Build from hash

Look up a single MD5 in the database:

python scripts/generate_pack.py --from-md5 d8f1206299c48946e6ec5ef96d014eaa

Build a pack containing only files matching hashes from a list (one MD5 per line, # for comments):

python scripts/generate_pack.py --platform batocera --from-md5-file missing.txt

This is useful when a platform reports missing files and you want to generate a targeted pack rather than re-downloading the full archive.

Split packs

Generate one ZIP per system instead of a single monolithic pack:

python scripts/generate_pack.py --platform retroarch --split

Group the split ZIPs by manufacturer (Sony, Nintendo, Sega, etc.):

python scripts/generate_pack.py --platform retroarch --split --group-by manufacturer

System-specific packs

Extract only the files for a single system within a platform:

python scripts/generate_pack.py --platform retroarch --system sony-playstation

Required only

Exclude optional files from the pack:

python scripts/generate_pack.py --platform batocera --required-only

What counts as "required" depends on the platform YAML. For existence-mode platforms (RetroArch), the distinction comes from the .info file's required field. For MD5-mode platforms (Batocera), all declared files are treated as required unless explicitly marked optional.

Region filtering

Keep one regional BIOS per system instead of all of them:

python scripts/generate_pack.py --platform retroarch --region us
python scripts/generate_pack.py --platform retroarch --region us,eu,jp

The list is an ordered priority, best first, the same model ROM managers use for 1G1R. --region us,eu,jp means prefer North America, fall back to Europe, fall back to Japan. It does not mean "keep all three": when a US BIOS exists for a system, the European and Japanese ones are dropped.

Accepted names are territory slugs (japan, north-america, europe, south-korea, taiwan, brazil, france...) plus short aliases (jp, us, eu, kr) and the signal spellings (ntsc-j, ntsc-u, pal). Territories nest, so --region europe keeps a BIOS declared [france], and --region france keeps one declared [europe].

Three rules keep a filtered pack usable:

• No system is ever emptied. If nothing matches, the whole group is kept. --region us still ships disksys.rom, because the Famicom Disk System has no American BIOS.
• Region-free files always survive. psxonpsp660.bin, ps1_rom.bin and openbios.bin are declared [world]; they add a capability rather than competing regionally.
• Untagged files always survive. Most BIOS are not regional and carry no region: at all.

What this does and does not do: it shrinks the pack. It does not change how cores pick a BIOS. Most cores already select per region from fixed filename lists driven by the game's region (PicoDrive in libretro.c, Genesis Plus GX in loadrom.c), so a USA game already gets the US BIOS when it is present. Only cores that load a single unqualified file change behaviour. Loading imports from another region may need the unfiltered pack.

Verification takes the same flag, and needs it: a filtered pack checked without it reports every dropped file as missing.

python scripts/generate_pack.py --platform recalbox --region us --verify-packs

--region composes with --split, --target, --required-only, --source, --emulator and --system. It is mutually exclusive with --from-md5, which selects by hash. pipeline.py never passes it, so the released packs stay complete.

Pack Source Variants

A pack is built from two file sources: the platform's own declared list (layer 1) and the requirements of the emulator profiles that apply to it (layer 3). --source selects which of the two contributes.

--source	Contents	Name suffix
full (default)	platform baseline plus everything its cores need	none
platform	only what the platform itself declares	_Platform
truth	only what the emulator profiles require	_Truth

--required-only crosses with each of them and adds _Required:

python scripts/generate_pack.py --platform retroarch --source platform
python scripts/generate_pack.py --platform retroarch --source truth --required-only
python scripts/generate_pack.py --all --all-variants --output-dir dist/

--all-variants builds all six combinations in one run, producing names like RetroArch_Lakka_v1.22.2_BIOS_Pack.zip, RetroArch_Lakka_v1.22.2_Platform_BIOS_Pack.zip and RetroArch_Lakka_v1.22.2_Truth_Required_BIOS_Pack.zip.

Which one to pick: full is the one to ship, since it covers alternate cores and optional firmware. platform is much smaller and matches exactly what the frontend checks for, which suits SD cards and handhelds. truth is a diagnostic build: it shows what the emulator source code asks for, independent of what the platform declares, and is how a gap between the two becomes visible.

Variants compose with --split, --target and --manifest.

Hardware Target Filtering

What targets are

A target represents a hardware architecture where a platform runs. Each architecture has a different set of available cores. For example, the RetroArch Switch target has fewer cores than the x86_64 target because some cores are not ported to ARM.

Target data is scraped from upstream sources (buildbot nightly listings, board configs, scriptmodules) and stored in platforms/targets/<platform>.yml.

Usage

Filter packs or verification to only include systems reachable by cores available on the target hardware:

python scripts/generate_pack.py --platform retroarch --target switch
python scripts/generate_pack.py --all --target x86_64
python scripts/verify.py --platform batocera --target rpi4

When combined with --all, platforms that define the target are filtered. Platforms without a target file for that name are left unfiltered (no information to exclude anything). Platforms that have target data but not the requested target are skipped with an INFO message.

How it works

The filtering pipeline has three stages:

1. load_target_config() reads platforms/targets/<platform>.yml and returns the set of cores available on the target. Aliases from _overrides.yml are resolved (e.g., --target rpi4 may match bcm2711 in the target file).

2. resolve_platform_cores() determines which emulator profiles are relevant for the platform, then intersects the result with the target's core set. The intersection uses a reverse index built from each profile's cores: field, so that upstream names (e.g., mednafen_psx on the buildbot) map to profile keys (e.g., beetle_psx).

3. filter_systems_by_target() removes platform systems where every core that emulates them is absent from the target. Systems with no core information are kept (benefit of the doubt). System ID normalization strips manufacturer prefixes and separators so that xbox matches microsoft-xbox.

List available targets

python scripts/verify.py --platform retroarch --list-targets

Overrides

platforms/targets/_overrides.yml provides two mechanisms:

• Aliases: map user-facing names to internal target IDs (e.g., rpi4 -> bcm2711).
• add/remove cores: patch the scraped core list for a specific target without overwriting the entire file. Useful when a core is known to work but is not listed on the buildbot, or vice versa.

Single-target platforms

Platforms with only one target (e.g., RetroBat with windows, RomM with browser) treat --target <their-only-target> as a no-op: the output is identical to running without --target.

Truth Generation and Diffing

What truth is

Truth data is ground truth generated from emulator profiles. It represents what each core actually needs based on source code analysis, independent of what platform scrapers declare. The purpose is gap analysis: finding files that platforms miss or declare incorrectly.

Generate truth

Build truth YAMLs from emulator profiles for a platform or all platforms:

python scripts/generate_truth.py --platform retroarch
python scripts/generate_truth.py --all --output-dir dist/truth/

Each truth YAML lists every system with its files, hashes, and the emulator profiles that reference them. The output mirrors the platform YAML structure so the two can be diffed directly.

Diff truth vs scraped

Find divergences between generated truth and scraped platform data:

python scripts/diff_truth.py --platform retroarch
python scripts/diff_truth.py --all

The diff reports:

• Files present in truth but absent from the platform YAML (undeclared).
• Files present in the platform YAML but absent from truth (orphaned or from cores not profiled yet).
• Hash mismatches between truth and platform data.

Export to native formats

Convert truth data to the native format each platform consumes:

python scripts/export_native.py --platform batocera    # Python dict (batocera-systems)
python scripts/export_native.py --platform recalbox    # XML (es_bios.xml)
python scripts/export_native.py --all --output-dir dist/upstream/

This allows submitting corrections upstream in the format maintainers expect.

Emulator-Level Verification

Per-emulator checks

Verify files against a single emulator's ground truth (size, hashes, crypto):

python scripts/verify.py --emulator handy
python scripts/verify.py --emulator handy --verbose

Default output shows aggregate results per file: the core name and which checks apply. With --verbose, each file expands to one line per core with the exact validation parameters and source code reference:

lynxboot.img
  handy validates size=512 crc32=0x0d973c9d [src/handy/system.h:45]

Per-system checks

Aggregate verification across all cores that emulate a system:

python scripts/verify.py --system atari-lynx

Standalone mode

Some cores have both libretro and standalone modes with different file requirements. Filter to standalone-only:

python scripts/verify.py --emulator dolphin --standalone

Ground truth in verbose output

The verbose report includes a coverage footer:

Ground truth: 142/160 files have emulator validation (88%)

This indicates how many files in the platform can be cross-checked against source-verified emulator profiles. Files without ground truth rely solely on platform-level verification. JSON output (--json) always includes the full per-emulator detail regardless of verbosity.

Offline Workflow

Full offline pipeline

Run the entire pipeline without network access:

python scripts/pipeline.py --offline

This skips data directory refresh, MAME/FBNeo hash fetch, and buildbot staleness checks. All other steps (database generation, verification, pack building, consistency check, README, site generation) run normally using cached data.

Partial runs

Skip pack generation when you only need verification results:

python scripts/pipeline.py --offline --skip-packs

Skip documentation generation:

python scripts/pipeline.py --offline --skip-docs

Truth pipeline

Include truth generation and diffing in the pipeline:

python scripts/pipeline.py --offline --with-truth

Include truth + native format export:

python scripts/pipeline.py --offline --with-export

Combining flags

Flags compose freely:

python scripts/pipeline.py --offline --skip-docs --with-truth --target switch

This runs: database generation, verification (filtered to Switch cores), truth generation and diff, consistency check. Packs and docs are skipped, no network access.