openmixer

omx-panel

Worked example: a third-party LV2 and CLAP plugin to a generated panel, adapted to Zynthian

The project's own text, in English. The source of this page

Worked example: a third-party LV2 and CLAP plugin to a generated panel, adapted to Zynthian

This takes two plugins nobody here wrote, as a distribution installs them, through the whole panel path: the scan into a descriptor, the layout, the MOD GUI and the test that holds it to the descriptor. It then follows the LV2 one to where Zynthian looks for it.

  • LV2: ZamComp, Damien Zammit's mono compressor (urn:zamaudio:ZamComp), from Fedora's lv2-zam-plugins. Section 4 reads, from Zynthian's sources, where it would look for it.
  • CLAP: LSP Limiter Mono (in.lsp-plug.limiter_mono), from Fedora's lsp-plugins-clap.

Every command below was run as written, from the root of this repository, and its output is shown under it, or is the committed file it writes under examples/worked-example/. What each command printed is also committed, one file per command, in examples/worked-example/transcript/, written by repeat.sh (run it after the setup of the next section; a command that prints nothing leaves no file). The output shown here is that transcript, line for line. A [exit N] line is the command's exit status when it is not 0. The rpm -q and lv2ls lines and the package versions are those of the container the run was made in. Nothing here was run on a Zynthian or a MOD: the last section says what comes from Zynthian's sources and what is still to be seen on one.

Where it ran

A Fedora 44 container (the openmixer-worker image, whose packages the commands below upgrade), the Fedora repositories and the FreeMixer channel enabled. The image also carries a copr repository, which the installs leave out so that every plugin comes from Fedora itself. As root:

dnf -y -q --disablerepo=copr-ycollet-audinux install lv2-zam-plugins lsp-plugins-clap omx-clap-host plugin-hostd plugin-hostd-devel omx-contract-devel
dnf -y -q --disablerepo=copr-ycollet-audinux upgrade omx-contract omx-contract-devel omx-clap-host omx-clap-core plugin-hostd plugin-hostd-devel
ln -s "$PWD/bin/omx-panel.mjs" /usr/local/bin/omx-panel
dnf -y -q --disablerepo=copr-ycollet-audinux install omx-panel

and, as the user, npm ci --silent in this checkout.

On a stock Fedora 44, the OpenMixer channel comes first, as this repository's CI adds it (dnf install https://www.openmixer.org/rpm/openmixer-release.noarch.rpm; not run here, the image carries the channel), and python3-lilv and sord are installed with the rest (the image carries them: python3-lilv-0.26.4, sord-0.16.22, lv2-1.18.10).

omx-panel is this checkout, run as omx-panel through the link above (/usr/local/bin comes before /usr/bin on the path). The commands ran at 3ebf9b7, the commit that adds repeat.sh; its omx-panel is origin/main at 15cc25bb9 (pull request 26 merged, so the readout fix of omx-panel#25 is in), and the branch adds only the example, this document, a line of the README and the exemption of the example's output files in tools/check-spdx.mjs. The released omx-panel 0.2.5, installed last, is run as /usr/bin/omx-panel once: it stops on ZamComp (section 3). Every other command runs as an unprivileged user.

1. The plugins as installed

$ mkdir -p examples/worked-example/zamcomp examples/worked-example/lsp-limiter-mono

$ rpm -q lv2-zam-plugins lsp-plugins-clap
lv2-zam-plugins-4.4-7.fc44.x86_64
lsp-plugins-clap-1.2.29-1.fc44.x86_64

$ rpm -ql lv2-zam-plugins | grep '^/usr/lib64/lv2/ZamComp.lv2/'
/usr/lib64/lv2/ZamComp.lv2/ZamComp_dsp.so
/usr/lib64/lv2/ZamComp.lv2/ZamComp_dsp.ttl
/usr/lib64/lv2/ZamComp.lv2/ZamComp_ui.so
/usr/lib64/lv2/ZamComp.lv2/ZamComp_ui.ttl
/usr/lib64/lv2/ZamComp.lv2/manifest.ttl
/usr/lib64/lv2/ZamComp.lv2/presets.ttl

$ rpm -qf /usr/lib64/clap/lsp-plugins.clap
lsp-plugins-clap-1.2.29-1.fc44.x86_64

$ lv2ls | grep -x urn:zamaudio:ZamComp
urn:zamaudio:ZamComp

$ lv2info urn:zamaudio:ZamComp > examples/worked-example/zamcomp/lv2info.txt

$ omx-clap-scan /usr/lib64/clap/lsp-plugins.clap | sed -n '/^  plugin in.lsp-plug.limiter_mono /,/^    note ports/p' > examples/worked-example/lsp-limiter-mono/omx-clap-scan.txt

zamcomp/lv2info.txt is ZamComp as lilv reads it: three audio ports, eight input controls (att, rel, kn, rat, thr, mak, slew, sidech, ports 3 to 10) and two output controls, the readouts gr (gain reduction) and outlevel (ports 11 and 12). lilv lists the three presets in an order that changes from run to run, so a repeat can differ from the committed file in those three lines and nowhere else. lsp-limiter-mono/omx-clap-scan.txt is the limiter as omx-clap-scan lists it, version 1.0.33, 28 parameters; the scan of the whole lsp-plugins.clap lists every plugin the file holds, and sed keeps this one.

2. The scan into a descriptor

One step writes a scanned descriptor (omx-contract docs/descriptors.md) for either format: plugin-hostd-probe describe (plugin-hostd 0.7.0 and later, its docs/formats.md). It runs omx-clap-core's omx-clap-scan --fields, the dump of every field one CLAP or LV2 plugin states, read as a host reads it (for LV2, through lilv), and maps each field to a descriptor word by plugin-hostd's format tables. So the LV2 scan to a descriptor exists, and it is the same step as the CLAP one.

$ rpm -q omx-clap-host omx-clap-core plugin-hostd omx-contract
omx-clap-host-0.20.1-1.fc44.x86_64
omx-clap-core-0.20.1-1.fc44.x86_64
plugin-hostd-0.10.0-1.fc44.x86_64
omx-contract-3.1.0-1.fc44.noarch

$ omx-clap-scan --fields lv2:urn:zamaudio:ZamComp > examples/worked-example/zamcomp/zamcomp.fields.tsv

$ plugin-hostd-probe describe lv2:urn:zamaudio:ZamComp > examples/worked-example/zamcomp/zamcomp.descriptor.json

$ omx-clap-scan --fields clap:/usr/lib64/clap/lsp-plugins.clap#in.lsp-plug.limiter_mono > examples/worked-example/lsp-limiter-mono/limiter_mono.fields.tsv

$ plugin-hostd-probe describe clap:/usr/lib64/clap/lsp-plugins.clap#in.lsp-plug.limiter_mono > examples/worked-example/lsp-limiter-mono/limiter_mono.descriptor.json

The dumps are the committed .fields.tsv files, the descriptors the .descriptor.json beside them. What a scan cannot know, it writes as unknown:

  • every control's meaning is unknown (neither format states what a control means), so the layout infers no family and no roles: both plugins are family none;
  • ZamComp's units are its TTL's (ms, dB), its rat and slew state none (unknown); gr and outlevel are readonly, with a range and no default;
  • the limiter's controls are keyed by CLAP parameter id, a number; their units are unknown and their scales unknown or stepped, as CLAP states neither.

3. The layout and the MOD GUI

ZamComp, with no panel file

$ omx-panel layout --descriptor examples/worked-example/zamcomp/zamcomp.descriptor.json > examples/worked-example/zamcomp/zamcomp.layout.json

$ omx-panel layout --descriptor examples/worked-example/zamcomp/zamcomp.descriptor.json --pages | tee examples/worked-example/zamcomp/zamcomp.pages.json
[
  {
    "section": 0,
    "sectionName": "Controls",
    "pageName": "Controls 1",
    "ids": [
      "att",
      "rel",
      "kn",
      "rat",
      "thr",
      "mak",
      "slew",
      "sidech"
    ]
  },
  {
    "section": 0,
    "sectionName": "Controls",
    "pageName": "Controls 2",
    "ids": [
      "gr",
      "outlevel",
      null,
      null,
      null,
      null,
      null,
      null
    ]
  }
]

ZamComp's TTL states no port groups, so every control is in the one section Controls, in port order, cut into pages of eight (the page rule of docs/panel-layout.md). The two readouts take the second page: the layout pages every control it lists, a readout included.

$ omx-panel modgui --descriptor examples/worked-example/zamcomp/zamcomp.descriptor.json --out examples/worked-example/zamcomp/no-panel/ZamComp.lv2
modgui: wrote examples/worked-example/zamcomp/no-panel/ZamComp.lv2/modgui.ttl
modgui: wrote examples/worked-example/zamcomp/no-panel/ZamComp.lv2/modgui/icon-ZamComp.html
modgui: wrote examples/worked-example/zamcomp/no-panel/ZamComp.lv2/modgui/stylesheet-ZamComp.css
modgui: wrote examples/worked-example/zamcomp/no-panel/ZamComp.lv2/modgui/screenshot-ZamComp.png
modgui: wrote examples/worked-example/zamcomp/no-panel/ZamComp.lv2/modgui/thumbnail-ZamComp.png
modgui: wrote examples/worked-example/zamcomp/no-panel/ZamComp.lv2/modgui/knobs/omx-knob.png

$ tools/modgui-test.sh examples/worked-example/zamcomp/no-panel/ZamComp.lv2 examples/worked-example/zamcomp/zamcomp.descriptor.json
PASS modgui-gen --check ZamComp
PASS template draws att with its declared travel and default
PASS template draws rel with its declared travel and default
PASS template draws kn with its declared travel and default
PASS template draws rat with its declared travel and default
PASS template draws thr with its declared travel and default
PASS template draws mak with its declared travel and default
PASS template draws slew with its declared travel and default
PASS template draws sidech with its declared travel and default
PASS template draws readout gr as a display with its declared range
PASS template draws readout outlevel as a display with its declared range
PASS template draws exactly the 10 declared parameters
PASS sord_validate ZamComp.lv2/*.ttl against the LV2 specs, modgui terms and resource-hint terms (Found 21 errors among 85 files (checked 1947 restrictions); all 21 the label errors of omx-contract#144)
PASS sord_validate refuses a modgui property outside modgui-terms.ttl
PASS a moved default makes modgui-gen --check fail

The eight input controls are knobs (none is a toggle or a choice in the TTL), the two readouts displays (docs/modgui.md); modgui.ttl lists the eight as modgui:port.

ZamComp, with a panel file

zamcomp/zamcomp.panel.json is a panel written for this example: the detector controls in one section, the makeup gain in a second as a fader, the two readouts in a third. Its family is none: a declared dynamics would be refused, since no control of the scan carries the meaning threshold or ratio (docs/panel-layout.md, the family).

$ omx-panel layout --descriptor examples/worked-example/zamcomp/zamcomp.descriptor.json --panel examples/worked-example/zamcomp/zamcomp.panel.json --pages | tee examples/worked-example/zamcomp/zamcomp.panel.pages.json
[
  {
    "section": 0,
    "sectionName": "Detector",
    "pageName": "Detector",
    "ids": [
      "thr",
      "rat",
      "kn",
      "att",
      "rel",
      "slew",
      "sidech",
      null
    ]
  },
  {
    "section": 1,
    "sectionName": "Output",
    "pageName": "Output",
    "ids": [
      "mak",
      null,
      null,
      null,
      null,
      null,
      null,
      null
    ]
  },
  {
    "section": 2,
    "sectionName": "Meters",
    "pageName": "Meters",
    "ids": [
      "gr",
      "outlevel",
      null,
      null,
      null,
      null,
      null,
      null
    ]
  }
]

$ omx-panel modgui --descriptor examples/worked-example/zamcomp/zamcomp.descriptor.json --panel examples/worked-example/zamcomp/zamcomp.panel.json --out examples/worked-example/zamcomp/with-panel/ZamComp.lv2
modgui: wrote examples/worked-example/zamcomp/with-panel/ZamComp.lv2/modgui.ttl
modgui: wrote examples/worked-example/zamcomp/with-panel/ZamComp.lv2/modgui/icon-ZamComp.html
modgui: wrote examples/worked-example/zamcomp/with-panel/ZamComp.lv2/modgui/stylesheet-ZamComp.css
modgui: wrote examples/worked-example/zamcomp/with-panel/ZamComp.lv2/modgui/screenshot-ZamComp.png
modgui: wrote examples/worked-example/zamcomp/with-panel/ZamComp.lv2/modgui/thumbnail-ZamComp.png
modgui: wrote examples/worked-example/zamcomp/with-panel/ZamComp.lv2/modgui/knobs/omx-knob.png
modgui: wrote examples/worked-example/zamcomp/with-panel/ZamComp.lv2/modgui/knobs/omx-fader.png

$ tools/modgui-test.sh examples/worked-example/zamcomp/with-panel/ZamComp.lv2 examples/worked-example/zamcomp/zamcomp.descriptor.json examples/worked-example/zamcomp/zamcomp.panel.json
PASS modgui-gen --check ZamComp
PASS template draws thr with its declared travel and default
PASS template draws rat with its declared travel and default
PASS template draws kn with its declared travel and default
PASS template draws att with its declared travel and default
PASS template draws rel with its declared travel and default
PASS template draws slew with its declared travel and default
PASS template draws sidech with its declared travel and default
PASS template draws mak with its declared travel and default
PASS template draws readout gr as a display with its declared range
PASS template draws readout outlevel as a display with its declared range
PASS template draws exactly the 10 declared parameters
PASS sord_validate ZamComp.lv2/*.ttl against the LV2 specs, modgui terms and resource-hint terms (Found 21 errors among 85 files (checked 1938 restrictions); all 21 the label errors of omx-contract#144)
PASS sord_validate refuses a modgui property outside modgui-terms.ttl
PASS a moved default makes modgui-gen --check fail

With the panel, modgui.ttl lists the seven controls of the first section, Detector, as modgui:port, and the makeup fader brings its own film strip.

The released 0.2.5 on ZamComp

$ rpm -q omx-panel
omx-panel-0.2.5-1.fc44.noarch

$ /usr/bin/omx-panel modgui --descriptor examples/worked-example/zamcomp/zamcomp.descriptor.json --out /tmp/zamcomp-0.2.5.lv2 2>&1 | grep '^Error'
Error: modgui-gen: 'gr' is not a declared control input with a travel

That is omx-panel#25: 0.2.5 looks a travel up for a readout. This checkout carries the fix.

LSP Limiter Mono, a CLAP plugin

$ omx-panel layout --descriptor examples/worked-example/lsp-limiter-mono/limiter_mono.descriptor.json > examples/worked-example/lsp-limiter-mono/limiter_mono.layout.json

$ omx-panel layout --descriptor examples/worked-example/lsp-limiter-mono/limiter_mono.descriptor.json --pages > examples/worked-example/lsp-limiter-mono/limiter_mono.pages.json

$ omx-panel modgui --descriptor examples/worked-example/lsp-limiter-mono/limiter_mono.descriptor.json --out /tmp/limiter_mono.lv2 2>&1 | grep '^Error'
Error: modgui-gen: 'in.lsp-plug.limiter_mono' states no LV2 URI; a MOD GUI belongs to an LV2 bundle

The limiter's 28 controls state no group, so they are one section Controls, four pages of eight, the last holding four (limiter_mono.pages.json, each slot a CLAP parameter id). These are the pages a CLAP host shows through clap.remote-controls. A MOD GUI belongs to an LV2 bundle, so the generator refuses a CLAP descriptor by name; lsp-plugins also ships an LV2 build, which would be scanned as lv2:<uri> and go the way of ZamComp.

Not every lsp CLAP plugin lays out yet. Filter Mono has two parameters named "Filter mode", and a CLAP control, whose id is a number, is keyed by its name:

$ plugin-hostd-probe describe clap:/usr/lib64/clap/lsp-plugins.clap#in.lsp-plug.filter_mono > examples/worked-example/lsp-limiter-mono/filter_mono.descriptor.json

$ omx-panel layout --descriptor examples/worked-example/lsp-limiter-mono/filter_mono.descriptor.json --pages
omx-panel: examples/worked-example/lsp-limiter-mono/filter_mono.descriptor.json: 'Filter mode' is a control twice
[exit 1]

That is omx-panel#27. survey-lsp-mono.sh scans and lays out every mono plugin of the file:

$ bash examples/worked-example/survey-lsp-mono.sh
refused in.lsp-plug.filter_mono: omx-panel: <descriptor>: 'Filter mode' is a control twice
refused in.lsp-plug.sampler_mono: omx-panel: <descriptor>: 'Sample pitch' is a control twice
refused in.lsp-plug.trigger_midi_mono: omx-panel: <descriptor>: 'Sample pitch' is a control twice
refused in.lsp-plug.trigger_mono: omx-panel: <descriptor>: 'Sample pitch' is a control twice
59 laid out, 4 refused

With --all it also lists the 59 plugins that lay out, one ok line each (transcript/27a-survey-lsp-mono-all.txt). The four refusals have the cause of Filter Mono's, a name two parameters share.

4. Zynthian

What follows comes from Zynthian's sources (zynthian-ui f46b018 and zynthian-sys 0774a58, both on their vangelis branch; zynthian-plugins 648c84a, its master), the omx-plugins README, and the lilv runs shown. Each file and line cited is at those commits. None of it was seen on a Zynthian.

Where Zynthian looks for LV2 bundles and their MOD GUIs

  • LV2_PATH is /usr/lib/lv2:/usr/lib/arm-linux-gnueabihf/lv2:/usr/local/lib/lv2:$ZYNTHIAN_PLUGINS_DIR/lv2: $ZYNTHIAN_DATA_DIR/presets/lv2:$ZYNTHIAN_MY_DATA_DIR/presets/lv2 (zynthian-sys scripts/zynthian_envars.sh:107), with ZYNTHIAN_PLUGINS_DIR /zynthian/zynthian-plugins (:105). zynthian-ui loads it with lilv's world.load_all() (zyngine/zynthian_lv2.py:213).
  • A bundle a user adds goes to /zynthian/zynthian-plugins/lv2 (LV2_DIR, zynthian_lv2.py:197): the webconf upload copies it there through add_engine (zynthian_lv2.py:386), and the omx-plugins README has a Zynthian without the apt channel copy its lv2/ bundles there and rescan the LV2 plugins from the admin menu. A plugin the rescan finds for the first time is disabled until enabled (zynthian_lv2.py:619).
  • The last commit of the zynthian-plugins repository (directories dssi, ladspa, lv2, vst) is 648c84a, dated 2016-09-21. The image's setup script installs LV2 plugins with apt-get, and the list names zam-plugins (zynthian-sys scripts/setup_plugins_rbpi.sh:42-52, the name on line 52); the recipe that builds zam-plugins from source, scripts/recipes/install_zam.sh, is commented out at setup_plugins_rbpi.sh:94. That the Debian package carries the same ZamComp as Fedora's, and puts it in /usr/lib/lv2, is not read from these sources.
  • A MOD GUI is drawn by MOD-UI, which Zynthian runs as an engine of its own (zynthian-ui zyngine/zynthian_engine_modui.py; zynthian's mod-ui fork, scripts/recipes/install_mod-ui.sh, run by setup_system_raspioslite_64bit_trixie.sh:562). Its service takes an LV2_PATH (etc/systemd/mod-ui.service:11) that scripts/update_zynthian_sys.sh:527 fills from the value set at :188: the same directories as above plus /usr/lib/$arch_libdir/lv2 and $ZYNTHIAN_PLUGINS_DIR/lv2-presets.

How the bundle gets there

A MOD GUI is read only when the bundle's manifest names modgui.ttl, and only from the bundle lilv takes the plugin from. Both are shown on a copy of the installed bundle:

$ rm -rf /tmp/stage && mkdir -p /tmp/stage

$ cp -R /usr/lib64/lv2/ZamComp.lv2 /tmp/stage/

$ cp -R examples/worked-example/zamcomp/with-panel/ZamComp.lv2/modgui.ttl examples/worked-example/zamcomp/with-panel/ZamComp.lv2/modgui /tmp/stage/ZamComp.lv2/

$ LV2_PATH=/tmp/stage python3 examples/worked-example/lilv-modgui.py urn:zamaudio:ZamComp
plugin  urn:zamaudio:ZamComp
bundle  file:///tmp/stage/ZamComp.lv2/
modgui:gui  none
[exit 1]

$ printf '\n<urn:zamaudio:ZamComp> rdfs:seeAlso <modgui.ttl> .\n' >> /tmp/stage/ZamComp.lv2/manifest.ttl

$ LV2_PATH=/tmp/stage python3 examples/worked-example/lilv-modgui.py urn:zamaudio:ZamComp
plugin  urn:zamaudio:ZamComp
bundle  file:///tmp/stage/ZamComp.lv2/
modgui:resourcesDirectory  file:///tmp/stage/ZamComp.lv2/modgui
modgui:iconTemplate  file:///tmp/stage/ZamComp.lv2/modgui/icon-ZamComp.html
modgui:stylesheet  file:///tmp/stage/ZamComp.lv2/modgui/stylesheet-ZamComp.css
modgui:screenshot  file:///tmp/stage/ZamComp.lv2/modgui/screenshot-ZamComp.png
modgui:thumbnail  file:///tmp/stage/ZamComp.lv2/modgui/thumbnail-ZamComp.png
modgui:brand  Damien Zammit
modgui:label  ZamComp
modgui:port  0 thr
modgui:port  1 rat
modgui:port  2 kn
modgui:port  3 att
modgui:port  4 rel
modgui:port  5 slew
modgui:port  6 sidech

$ LV2_PATH=/usr/lib64/lv2:/tmp/stage python3 examples/worked-example/lilv-modgui.py urn:zamaudio:ZamComp
lilv_world_compare_versions(): warning: Ignoring duplicate version 6.0 of <urn:zamaudio:ZamComp> from <file:///tmp/stage/ZamComp.lv2/>
lilv_world_compare_versions(): note: Previously loaded from <file:///usr/lib64/lv2/ZamComp.lv2/>
plugin  urn:zamaudio:ZamComp
bundle  file:///usr/lib64/lv2/ZamComp.lv2/
modgui:gui  none
[exit 1]

$ LV2_PATH=/tmp/stage:/usr/lib64/lv2 python3 examples/worked-example/lilv-modgui.py urn:zamaudio:ZamComp | head -3
lilv_world_compare_versions(): warning: Ignoring duplicate version 6.0 of <urn:zamaudio:ZamComp> from <file:///usr/lib64/lv2/ZamComp.lv2/>
lilv_world_compare_versions(): note: Previously loaded from <file:///tmp/stage/ZamComp.lv2/>
plugin  urn:zamaudio:ZamComp
bundle  file:///tmp/stage/ZamComp.lv2/
modgui:resourcesDirectory  file:///tmp/stage/ZamComp.lv2/modgui

lilv-modgui.py asks lilv, the library mod-ui reads LV2 data with, for the plugin's modgui:gui. The manifest line is added by hand: omx-panel modgui leaves the manifest as it is (omx-panel#28). Of two bundles with one plugin URI and one version, lilv keeps the first on LV2_PATH and ignores the other.

The test over the whole staged bundle:

$ tools/modgui-test.sh /tmp/stage/ZamComp.lv2 examples/worked-example/zamcomp/zamcomp.descriptor.json examples/worked-example/zamcomp/zamcomp.panel.json
PASS modgui-gen --check ZamComp
PASS template draws thr with its declared travel and default
PASS template draws rat with its declared travel and default
PASS template draws kn with its declared travel and default
PASS template draws att with its declared travel and default
PASS template draws rel with its declared travel and default
PASS template draws slew with its declared travel and default
PASS template draws sidech with its declared travel and default
PASS template draws mak with its declared travel and default
PASS template draws readout gr as a display with its declared range
PASS template draws readout outlevel as a display with its declared range
PASS template draws exactly the 10 declared parameters
error: Object not in range <http://lv2plug.in/ns/lv2core#ExtensionData>

error: Use of undefined property
       urn:zamaudio:ZamComp
error: Property <http://moddevices.com/ns/mod#brand> has no label
       urn:zamaudio:ZamComp
error: Use of undefined property
       urn:zamaudio:ZamComp
error: Property <http://moddevices.com/ns/mod#label> has no label
       urn:zamaudio:ZamComp
error: Object not in range <http://lv2plug.in/ns/lv2core#ExtensionData>
FAIL sord_validate ZamComp.lv2/*.ttl (Found 27 errors among 89 files (checked 2194 restrictions))
PASS sord_validate refuses a modgui property outside modgui-terms.ttl
PASS a moved default makes modgui-gen --check fail
modgui-test: 1 check(s) failed
[exit 1]

The six errors besides the 21 of omx-contract#144 are ZamComp's own TTL's, and the installed bundle, untouched, has the same six against the same LV2 specifications:

$ for s in core port-props units urid atom worker ui options midi patch time log state buf-size parameters presets resize-port port-groups morph dynmanifest instance-access data-access event uri-map schemas; do set -- "$@" /usr/lib64/lv2/$s.lv2/*.ttl; done; sord_validate /usr/lib64/lv2/ZamComp.lv2/*.ttl "$@" 2>&1 | grep -A1 '^error'
error: Object not in range <http://lv2plug.in/ns/lv2core#ExtensionData>

--
error: Use of undefined property
       urn:zamaudio:ZamComp
--
error: Property <http://moddevices.com/ns/mod#brand> has no label
       urn:zamaudio:ZamComp
--
error: Use of undefined property
       urn:zamaudio:ZamComp
--
error: Property <http://moddevices.com/ns/mod#label> has no label
       urn:zamaudio:ZamComp
--
error: Object not in range <http://lv2plug.in/ns/lv2core#ExtensionData>

On a Zynthian where the Debian package has put ZamComp in /usr/lib/lv2/ZamComp.lv2 (not read from the sources, see above), that bundle is first on LV2_PATH, and a copy of the bundle in /zynthian/zynthian-plugins/lv2 would be ignored by lilv as above. add_engine refuses a plugin whose engine is already registered unless force is set (zynthian_lv2.py:411-424). The MOD GUI then goes into the bundle lilv takes: copy modgui.ttl and modgui/ from examples/worked-example/zamcomp/with-panel/ZamComp.lv2/ into /usr/lib/lv2/ZamComp.lv2/, append the same rdfs:seeAlso line to its manifest.ttl, and restart MOD-UI. That step was not run, and a zam-plugins upgrade would overwrite the manifest. The descriptor should be the scan of the Zynthian's own ZamComp, whose Debian version may differ from Fedora's 4.4.

What the encoder pages show

The pages of eight above are the layout's: what a CLAP host shows through clap.remote-controls. Zynthian's touchscreen does not read them. For an LV2 plugin hosted by jalv it builds its own screens of four (zynthian-ui zyngine/zynthian_engine.py, generate_ctrl_screens, lines 681 to 724):

  • the controls are the plugin's input control ports, in port order (zynthian_lv2.py:940, get_plugin_ports), sorted by lv2:displayPriority, and grouped by pg:group; ungrouped controls are the group Params;
  • each group is cut into screens of four, numbered from 1 when a group has more than four;
  • an audio effect with no bypass port of its own gets a bypass control, added last (zyngine/zynthian_engine_jalv.py:544);
  • output control ports are no controllers: a readout is never on a screen.

ZamComp states no port group and no display priority:

$ grep -c -E 'portgroups|pg:group|displayPriority' /usr/lib64/lv2/ZamComp.lv2/ZamComp_dsp.ttl
0
[exit 1]

So, by those rules, Zynthian shows ZamComp as Params 1 (Attack, Release, Knee, Ratio), Params 2 (Threshold, Makeup, Slew, Sidechain) and Params 3 (bypass), and neither gr nor outlevel. This is read from the source, not seen. The layout's sections do not reach Zynthian's screens: an LV2 bundle would carry them as pg:group in its TTL, which the MOD GUI generator does not write. The word clap appears in no file of zynthian-ui at f46b018 (grep -ri clap finds nothing), and in zynthian-sys at 0774a58 only once, in a name misspelt "Claption" in a plugin description (config/engine_config.json:7932), so those sources name no CLAP host or plugin and the limiter's pages are not shown there.

What is verified, and what is not

Verified, by the commands above: both plugins come from Fedora 44's own packages; plugin-hostd-probe describe writes a scanned descriptor of each; omx-panel layout lays out ZamComp with and without a panel file and the limiter, and stops on Filter Mono and three more of the 63 mono lsp plugins (omx-panel#27); omx-panel modgui writes ZamComp's MOD GUI with and without a panel file, each bundle passing tools/modgui-test.sh, and refuses the CLAP limiter by name; omx-panel 0.2.5 stops on ZamComp's readout (omx-panel#25); lilv reads the MOD GUI from a copy of the bundle once its manifest names modgui.ttl, and keeps the first of two bundles of one plugin on LV2_PATH.

Not verified:

  • anything on a Zynthian or a MOD: the bundle's install there, MOD-UI drawing the template, the screens of four, the rescan;
  • the template as mod-ui draws it in a browser: the tests read the template's text and its TTL, not a render;
  • the readouts' displays showing a value: the generated MOD GUI draws a frame, and a live reading needs a modgui:javascript, which is not generated (docs/modgui.md);
  • ZamComp's Debian build (Zynthian's) having the same ports as Fedora's;
  • the limiter's pages on a CLAP host with a controller.

openmixer

A software mixing console for Linux. The desk is the software; the browser is the surface.

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Licence

OpenMixer is free software under the GPL-3.0-or-later. Every package in the workspace carries the same licence.

Roland, Midas, Behringer, RME and the product names used here belong to their respective owners. OpenMixer is an independent project and is not affiliated with any of them.