ALSA backend: always register ports with systemic latency

and allow re-start to un/set reporting latency.

diff --git a/libs/backends/alsa/alsa_audiobackend.cc b/libs/backends/alsa/alsa_audiobackend.cc
index b3948f8342ccb5ef91e58f49b8c3912f49055fb4..efb5a6c4404d085d02bb83c34cabe8ae11720d8d 100644 (file)
--- a/libs/backends/alsa/alsa_audiobackend.cc
+++ b/libs/backends/alsa/alsa_audiobackend.cc
@@ -805,7 +805,14 @@ AlsaAudioBackend::_start (bool for_latency_measurement)
        }
 
        if (_active || _run) {
-               PBD::error << _("AlsaAudioBackend: already active.") << endmsg;
+               if (for_latency_measurement != _measure_latency) {
+                       _measure_latency = for_latency_measurement;
+                       update_systemic_audio_latencies();
+                       update_systemic_midi_latencies ();
+                       PBD::info << _("AlsaAudioBackend: reload latencies.") << endmsg;
+                       return NoError;
+               }
+               PBD::info << _("AlsaAudioBackend: already active.") << endmsg;
                return BackendReinitializationError;
        }
 
@@ -1043,6 +1050,7 @@ AlsaAudioBackend::stop ()
        delete _pcmi; _pcmi = 0;
        _midi_ins = _midi_outs = 0;
        release_device();
+       _measure_latency = false;
 
        return (_active == false) ? 0 : -1;
 }
@@ -1384,7 +1392,7 @@ AlsaAudioBackend::register_system_audio_ports()
        const uint32_t lcpp = (_periods_per_cycle - 2) * _samples_per_period;
 
        /* audio ports */
-       lr.min = lr.max = (_measure_latency ? 0 : _systemic_audio_input_latency);
+       lr.min = lr.max = (_systemic_audio_input_latency);
        for (int i = 1; i <= a_ins; ++i) {
                char tmp[64];
                snprintf(tmp, sizeof(tmp), "system:capture_%d", i);
@@ -1396,7 +1404,7 @@ AlsaAudioBackend::register_system_audio_ports()
                _system_inputs.push_back (ap);
        }
 
-       lr.min = lr.max = lcpp + (_measure_latency ? 0 : _systemic_audio_output_latency);
+       lr.min = lr.max = lcpp + (_systemic_audio_output_latency);
        for (int i = 1; i <= a_out; ++i) {
                char tmp[64];
                snprintf(tmp, sizeof(tmp), "system:playback_%d", i);
@@ -1479,7 +1487,7 @@ AlsaAudioBackend::register_system_midi_ports(const std::string device)
                                        delete mout;
                                }
                                LatencyRange lr;
-                               lr.min = lr.max = (_measure_latency ? 0 : nfo->systemic_output_latency);
+                               lr.min = lr.max = (nfo->systemic_output_latency);
                                set_latency_range (p, true, lr);
                                static_cast<AlsaMidiPort*>(p)->set_n_periods(_periods_per_cycle); // TODO check MIDI alignment
                                AlsaPort *ap = static_cast<AlsaPort*>(p);
@@ -1519,7 +1527,7 @@ AlsaAudioBackend::register_system_midi_ports(const std::string device)
                                        continue;
                                }
                                LatencyRange lr;
-                               lr.min = lr.max = (_measure_latency ? 0 : nfo->systemic_input_latency);
+                               lr.min = lr.max = (nfo->systemic_input_latency);
                                set_latency_range (p, false, lr);
                                AlsaPort *ap = static_cast<AlsaPort*>(p);
                                ap->set_pretty_name (replace_name_io (i->first, true));