Ok I got it. The LV2 Buf Size section in the docs is just the
specification of the buf size extension. The mechanism of access is
through the lv2 options:
typedef struct {
LV2_URID_Map *map;
LV2_URID samplerate;
LV2_URID buffersize;
} GuitarMidiURIDs;
static void map_options(LV2_URID_Map *map, GuitarMidiURIDs *urids)
{
urids->map = map;
urids->samplerate = map->map(map->handle,
LV2_CORE__sampleRate);
urids->buffersize = map->map(map->handle,
LV2_BUF_SIZE__maxBlockLength);
}
static LV2_Handle
instantiate(const LV2_Descriptor *descriptor,
double rate,
const char *bundle_path,
const LV2_Feature *const *features)
{
LV2_URID_Map *map = NULL;
LV2_Log_Log *log = NULL;
LV2_Options_Option *options = NULL;
printf("Loading plugin\n");
...
// map the options to get the sample rate and buffer size
GuitarMidiURIDs urids;
map_options(map, &urids);
auto buffer_size = BUFFER_SIZE;
// get the sample rate and buffer size from the host options
if (options){
for(int o=0;o<options[o].key;o++){
if(options[o].key==urids.samplerate){
rate=*((double*)options[o].value);
lv2_log_note(&g_logger,"Sample rate:
%f\n",rate);
}
else if (options[o].key==urids.buffersize){
buffer_size=*((uint32_t*)options[o].va
lue);
lv2_log_note(&g_logger,"Buffer size:
%d\n",buffer_size);
}
}}
... use the buffersize
}
Gerald
On Mon, 2026-06-15 at 11:56 +0200, gm-linuxaudio.privatize920 at
passmail.net wrote:
> Hi,
> Im at a loss trying to understand how to access runtime parameters in
> an lv2 plugin at init time. Specifically the buffer size.
> I understand the concept of the LV2_URIDs and have mapped the
> resource
> LV2_BUF_SIZE__maxBlockLength to its urid:
>
> typedef struct {
> LV2_URID_Map *map;
> LV2_URID samplerate;
> LV2_URID buffersize;
> } GuitarMidiURIDs;
>
>
> static void map_options(LV2_URID_Map *map, GuitarMidiURIDs *urids)
> {
> urids->map = map;
> urids->samplerate = map->map(map->handle,
> LV2_CORE__sampleRate);
> urids->buffersize = map->map(map->handle,
> LV2_BUF_SIZE__maxBlockLength);
> }
>
>
> Now I cant find in the examples how to actually get the buffersize
> given urids->buffersize. Can someone point me to a plugin where this
> is
> achieved?
> Thanks,
> Gerald
