How to Check Ecasound for LADSPA and JACK Support

This guide explains how to verify that an Ecasound installation or source build includes full support for both LADSPA plugins and the JACK Audio Connection Kit. You will learn how to inspect compile-time flags, query the ecasound binary for enabled subsystems, and run quick command-line tests to confirm that both audio interfaces operate correctly at runtime.

1. Check Compiled Feature Flags

The fastest way to determine which subsystems are compiled into your Ecasound binary is to pass the --version flag:

ecasound --version

Look at the output under the configuration features or libraries section. A build with full support will explicitly list both JACK and LADSPA among the enabled components. If either is missing, the binary was compiled without the necessary development headers (libjack-dev or ladspa-sdk).

If you are compiling from source, check the summary output at the conclusion of running ./configure:

./configure

Ensure the status report at the end displays:

JACK support: yes
LADSPA support: yes

If either shows no, inspect config.log to identify missing header files or linker dependencies before running make.

2. Verify Functional JACK Support

Even if compiled in, verify that the JACK driver initializes properly with the audio server.

Ensure your JACK server is running (e.g., via jackd or pipewire-jack).
Run a minimal test command routing null audio to a JACK output:

ecasound -i null -o jack

Results:

Success: Ecasound starts processing, registers its ports with the JACK graph, and displays the continuous engine status bar without errors.
Failure: If JACK support is missing entirely, Ecasound will exit with an error such as:
```
(eca-session) Unknown audio subsystem: 'jack'
```
If JACK support is compiled in but the server is not reachable, Ecasound will output an error stating it cannot connect to the JACK daemon, confirming the driver exists.

3. Verify Functional LADSPA Support

To confirm that the LADSPA subsystem functions, test Ecasound's ability to locate and instantiate a plugin.

Ensure you have standard LADSPA plugins installed (e.g., swh-plugins or tap-plugins) and that the LADSPA_PATH environment variable includes your plugin directory (commonly /usr/lib/ladspa or /usr/local/lib/ladspa).
Run Ecasound in interactive mode:

ecasound -c

At the ecasound> prompt, query available LADSPA plugins:

ladspa-list

Results:

Success: Ecasound prints a list of detected LADSPA unique IDs and plugin labels.
Failure: An error indicating Command not found or an empty list (when plugins are verified to be on the disk) indicates LADSPA support is disabled or not recognizing the plugin directory.

You can also run a direct non-interactive command applying a known plugin:

ecasound -i null -o null -el:amp_mono,1.0

If LADSPA is properly integrated, Ecasound will load the plugin without throwing an "unknown effect" or "subsystem not supported" error.