Hi,

I'm trying to use a LADSPA plugin in the pcm-plugin layer of the ALSA userspace library. However I get an error saying ALSA needs two control ports (input and output) while the plugin only has one input control port.

What could be the problem?

Thanks for your help

E-J

Below are all the details:

I'm running the software on a Blackfin DSP processor with uCLinux. The plugin is obtained from LADSPA org. The tools analyseplugin and applyplugin (as delivered within the LADSPA SDK) do work correctly. I use the amp.so plugin.

The error: ---------------------------------------------------------------------- Use 'aplay' with LADSPA plugin : error because of missing output control ---------------------------------------------------------------------- root:~> aplay -D myladspa test.wav Init AMP plugin AMP ladspa descriptor, index = 0 AMP ladspa descriptor, index = 1 ALSA lib ../../../alsa-lib-1.0.12/src/pcm/pcm_ladspa.c:1361:(snd_pcm_ladspa_parse_ioconfig) error adding default controls aplay: main:550: audio open error: Cannot allocate memory

The plugin info: ---------------------------------------------------------------------- AMP.SO plugin info ---------------------------------------------------------------------- root:~> analyseplugin amp.so Init AMP plugin AMP ladspa descriptor, index = 0

Plugin Name: "Mono Amplifier" Plugin Label: "amp_mono" Plugin Unique ID: 1048 Maker: "Richard Furse (LADSPA example plugins)" Copyright: "None" Must Run Real-Time: No Has activate() Function: No Has deactivate() Function: No Has run_adding() Function: No Environment: Normal or Hard Real-Time Ports: "Gain" input, control, 0 to ..., default 1, logarithmic <== one input control port "Input" input, audio "Output" output, audio AMP ladspa descriptor, index = 1

Plugin Name: "Stereo Amplifier" Plugin Label: "amp_stereo" Plugin Unique ID: 1049 Maker: "Richard Furse (LADSPA example plugins)" Copyright: "None" Must Run Real-Time: No Has activate() Function: No Has deactivate() Function: No Has run_adding() Function: No Environment: Normal or Hard Real-Time Ports: "Gain" input, control, 0 to ..., default 1, logarithmic <== one input control port "Input (Left)" input, audio "Output (Left)" output, audio "Input (Right)" input, audio "Output (Right)" output, audio AMP ladspa descriptor, index = 2

The config file: ---------------------------------------------------------------------- asound.conf ---------------------------------------------------------------------- pcm.myladspa{ type ladspa slave { pcm default }

path "/usr/lib/ladspa"; plugins [ { label "amp_stereo" filename "amp.so" policy "duplicate" output { controls[1] } input { controls[1] } } ] }

ctl.myladspa{ type hw card 0 }

ALSA always tries to open a input and output control port... ---------------------------------------------------------------------- pcm_ladspa.c ---------------------------------------------------------------------- --- snd_pcm_ladspa_parse_ioconfig is always called, for input AND output control --- in function snd_pcm_ladspa_add_plugin (line 1512):

err = snd_pcm_ladspa_parse_ioconfig(lplug, &lplug->input, input); if (err < 0) return err; err = snd_pcm_ladspa_parse_ioconfig(lplug, &lplug->output, output); if (err < 0) return err;

I think here might be an error or is it agreed a plugin ALWAYS has two control ports... ---------------------------------------------------------------------- pcm_ladspa.c ---------------------------------------------------------------------- --- if no output control found, calloc (0, sizeof...) results in -ENOMEM error ---

static int snd_pcm_ladspa_add_default_controls(snd_pcm_ladspa_plugin_t *lplug, snd_pcm_ladspa_plugin_io_t *io) { unsigned int count = 0; LADSPA_Data *array; unsigned char *initialized; unsigned long idx;

for (idx = 0; idx < lplug->desc->PortCount; idx++) if ((lplug->desc->PortDescriptors[idx] & (io->pdesc | LADSPA_PORT_CONTROL)) == (io->pdesc | LADSPA_PORT_CONTROL)) count++; array = (LADSPA_Data *)calloc(count, sizeof(LADSPA_Data)); if (!array) return -ENOMEM;