ALSA: allow to measure & set systemic audio latency w/o restart.

(MIDI needs a bit more work)

diff --git a/libs/backends/alsa/alsa_audiobackend.cc b/libs/backends/alsa/alsa_audiobackend.cc
index d0236327f3b475f532b7e9c039235b292f49d00f..25a5e3f12775860eae1c94eece7123d4fa708d04 100644 (file)
--- a/libs/backends/alsa/alsa_audiobackend.cc
+++ b/libs/backends/alsa/alsa_audiobackend.cc
@@ -483,6 +483,9 @@ int
 AlsaAudioBackend::set_systemic_input_latency (uint32_t sl)
 {
        _systemic_audio_input_latency = sl;
+       if (_run) {
+               update_systemic_audio_latencies();
+       }
        return 0;
 }
 
@@ -490,6 +493,9 @@ int
 AlsaAudioBackend::set_systemic_output_latency (uint32_t sl)
 {
        _systemic_audio_output_latency = sl;
+       if (_run) {
+               update_systemic_audio_latencies();
+       }
        return 0;
 }
 
@@ -499,6 +505,9 @@ AlsaAudioBackend::set_systemic_midi_input_latency (std::string const device, uin
        struct AlsaMidiDeviceInfo * nfo = midi_device_info(device);
        if (!nfo) return -1;
        nfo->systemic_input_latency = sl;
+       if (_run && nfo->enabled) {
+               update_systemic_midi_latencies ();
+       }
        return 0;
 }
 
@@ -508,9 +517,49 @@ AlsaAudioBackend::set_systemic_midi_output_latency (std::string const device, ui
        struct AlsaMidiDeviceInfo * nfo = midi_device_info(device);
        if (!nfo) return -1;
        nfo->systemic_output_latency = sl;
+       if (_run && nfo->enabled) {
+               update_systemic_midi_latencies ();
+       }
        return 0;
 }
 
+void
+AlsaAudioBackend::update_systemic_audio_latencies ()
+{
+       const uint32_t lcpp = (_periods_per_cycle - 2) * _samples_per_period;
+       LatencyRange lr;
+
+       lr.min = lr.max = lcpp + (_measure_latency ? 0 : _systemic_audio_input_latency);
+       for (std::vector<AlsaPort*>::const_iterator it = _system_outputs.begin (); it != _system_outputs.end (); ++it) {
+               set_latency_range (*it, true, lr);
+       }
+
+       lr.min = lr.max = (_measure_latency ? 0 : _systemic_audio_output_latency);
+       for (std::vector<AlsaPort*>::const_iterator it = _system_inputs.begin (); it != _system_inputs.end (); ++it) {
+               set_latency_range (*it, false, lr);
+       }
+       update_latencies ();
+}
+
+void
+AlsaAudioBackend::update_systemic_midi_latencies ()
+{
+#if 0
+       // TODO, need a way to associate the port with the corresponding AlsaMidiDeviceInfo
+       for (std::vector<AlsaPort*>::iterator it = _system_midi_out.begin (); it != _system_midi_out.end (); ++it) {
+               LatencyRange lr;
+               lr.min = lr.max = (_measure_latency ? 0 : nfo->systemic_output_latency);
+               set_latency_range (*it, false, lr);
+       }
+       for (std::vector<AlsaPort*>::const_iterator it = _system_midi_in.begin (); it != _system_midi_in.end (); ++it) {
+               LatencyRange lr;
+               lr.min = lr.max = (_measure_latency ? 0 : nfo->systemic_input_latency);
+               set_latency_range (*it, true, lr);
+       }
+#endif
+       update_latencies ();
+}
+
 /* Retrieving parameters */
 std::string
 AlsaAudioBackend::device_name () const
@@ -679,6 +728,7 @@ AlsaAudioBackend::set_midi_device_enabled (std::string const device, bool enable
        struct AlsaMidiDeviceInfo * nfo = midi_device_info(device);
        if (!nfo) return -1;
        nfo->enabled = enable;
+       // TODO - trigger update when already running
        return 0;
 }
 
@@ -1236,7 +1286,7 @@ AlsaAudioBackend::register_system_audio_ports()
        const int a_ins = _n_inputs;
        const int a_out = _n_outputs;
 
-       // TODO set latency depending on _periods_per_cycle and  _samples_per_period
+       const uint32_t lcpp = (_periods_per_cycle - 2) * _samples_per_period;
 
        /* audio ports */
        lr.min = lr.max = (_measure_latency ? 0 : _systemic_audio_input_latency);
@@ -1249,7 +1299,7 @@ AlsaAudioBackend::register_system_audio_ports()
                _system_inputs.push_back(static_cast<AlsaPort*>(p));
        }
 
-       lr.min = lr.max = (_measure_latency ? 0 : _systemic_audio_output_latency);
+       lr.min = lr.max = lcpp + (_measure_latency ? 0 : _systemic_audio_output_latency);
        for (int i = 1; i <= a_out; ++i) {
                char tmp[64];
                snprintf(tmp, sizeof(tmp), "system:playback_%d", i);
@@ -1311,7 +1361,7 @@ AlsaAudioBackend::register_system_midi_ports()
                                }
                                LatencyRange lr;
                                lr.min = lr.max = (_measure_latency ? 0 : nfo->systemic_output_latency);
-                               set_latency_range (p, false, lr);
+                               set_latency_range (p, true, lr);
                                static_cast<AlsaMidiPort*>(p)->set_n_periods(_periods_per_cycle); // TODO check MIDI alignment
                                _system_midi_out.push_back(static_cast<AlsaPort*>(p));
                                _rmidi_out.push_back (mout);

diff --git a/libs/backends/alsa/alsa_audiobackend.h b/libs/backends/alsa/alsa_audiobackend.h
index 1dca7ec14989f0a410d574ffdf8a41d61dcb5781..a661aa2979faaa26ec240a5f450c7a09dd60a029 100644 (file)
--- a/libs/backends/alsa/alsa_audiobackend.h
+++ b/libs/backends/alsa/alsa_audiobackend.h
@@ -184,6 +184,8 @@ class AlsaAudioBackend : public AudioBackend {
                bool can_change_sample_rate_when_running () const;
                bool can_change_buffer_size_when_running () const;
 
+               bool can_change_systemic_latency_when_running () const { return true; }
+
                int set_device_name (const std::string&);
                int set_input_device_name (const std::string&);
                int set_output_device_name (const std::string&);
@@ -443,6 +445,9 @@ class AlsaAudioBackend : public AudioBackend {
                        return NULL;
                }
 
+               void update_systemic_audio_latencies ();
+               void update_systemic_midi_latencies ();
+
 }; // class AlsaAudioBackend
 
 } // namespace