JACK: pass the latency test

See #2

soundio/soundio.h

@@ -1004,9 +1004,12 @@ SOUNDIO_EXPORT int soundio_outstream_clear_buffer(struct SoundIoOutStream *outst
 ///   device does not support pausing/unpausing.
 SOUNDIO_EXPORT int soundio_outstream_pause(struct SoundIoOutStream *outstream, bool pause);
 
-/// Obtain the total number of seconds that the next frame you write to the
+/// Obtain the total number of seconds that the next frame written after the
-/// outstream will take to become audible. This includes both software and
+/// last frame written with ::soundio_outstream_end_write will take to become
-/// hardware latency.
+/// audible. This includes both software and hardware latency. In other words,
+/// if you call this function directly after calling ::soundio_outstream_end_write,
+/// this gives you the number of seconds that the next frame written will take
+/// to become audible.
 ///
 /// This function must be called only from within SoundIoOutStream::write_callback.
 SOUNDIO_EXPORT int soundio_outstream_get_latency(struct SoundIoOutStream *outstream,

src/jack.cpp

@@ -214,6 +214,7 @@ static int refresh_devices_bare(SoundIoPrivate *si) {
             djp->full_name = soundio_str_dupe(port->full_name, port->full_name_len);
             djp->full_name_len = port->full_name_len;
             djp->channel_id = port->channel_id;
+            djp->latency_range = port->latency_range;
 
             if (!djp->full_name) {
                 jack_free(port_names);
@@ -469,6 +470,8 @@ static int outstream_open_jack(struct SoundIoPrivate *si, struct SoundIoOutStrea
     jack_on_shutdown(osj->client, outstream_shutdown_callback, os);
 
 
+    jack_nframes_t max_port_latency = 0;
+
     // register ports and map channels
     int connected_count = 0;
     for (int ch = 0; ch < outstream->layout.channel_count; ch += 1) {
@@ -490,11 +493,13 @@ static int outstream_open_jack(struct SoundIoPrivate *si, struct SoundIoOutStrea
             osjp->dest_port_name = djp->full_name;
             osjp->dest_port_name_len = djp->full_name_len;
             connected_count += 1;
+            max_port_latency = max(max_port_latency, djp->latency_range.max);
         }
     }
     // If nothing got connected, channel layouts aren't working. Just send the
     // data in the order of the ports.
     if (connected_count == 0) {
+        max_port_latency = 0;
         outstream->layout_error = SoundIoErrorIncompatibleDevice;
 
         int ch_count = min(outstream->layout.channel_count, dj->port_count);
@@ -503,9 +508,12 @@ static int outstream_open_jack(struct SoundIoPrivate *si, struct SoundIoOutStrea
             SoundIoDeviceJackPort *djp = &dj->ports[ch];
             osjp->dest_port_name = djp->full_name;
             osjp->dest_port_name_len = djp->full_name_len;
+            max_port_latency = max(max_port_latency, djp->latency_range.max);
         }
     }
 
+    osj->hardware_latency = max_port_latency / (double)outstream->sample_rate;
+
     return 0;
 }
 
@@ -575,7 +583,9 @@ static int outstream_clear_buffer_jack(struct SoundIoPrivate *si, struct SoundIo
 static int outstream_get_latency_jack(struct SoundIoPrivate *si, struct SoundIoOutStreamPrivate *os,
         double *out_latency)
 {
-    soundio_panic("TODO");
+    SoundIoOutStreamJack *osj = &os->backend_data.jack;
+    *out_latency = osj->hardware_latency;
+    return 0;
 }
 
 
@@ -684,6 +694,8 @@ static int instream_open_jack(struct SoundIoPrivate *si, struct SoundIoInStreamP
     }
     jack_on_shutdown(isj->client, instream_shutdown_callback, is);
 
+    jack_nframes_t max_port_latency = 0;
+
     // register ports and map channels
     int connected_count = 0;
     for (int ch = 0; ch < instream->layout.channel_count; ch += 1) {
@@ -705,11 +717,13 @@ static int instream_open_jack(struct SoundIoPrivate *si, struct SoundIoInStreamP
             isjp->source_port_name = djp->full_name;
             isjp->source_port_name_len = djp->full_name_len;
             connected_count += 1;
+            max_port_latency = max(max_port_latency, djp->latency_range.max);
         }
     }
     // If nothing got connected, channel layouts aren't working. Just send the
     // data in the order of the ports.
     if (connected_count == 0) {
+        max_port_latency = 0;
         instream->layout_error = SoundIoErrorIncompatibleDevice;
 
         int ch_count = min(instream->layout.channel_count, dj->port_count);
@@ -718,9 +732,12 @@ static int instream_open_jack(struct SoundIoPrivate *si, struct SoundIoInStreamP
             SoundIoDeviceJackPort *djp = &dj->ports[ch];
             isjp->source_port_name = djp->full_name;
             isjp->source_port_name_len = djp->full_name_len;
+            max_port_latency = max(max_port_latency, djp->latency_range.max);
         }
     }
 
+    isj->hardware_latency = max_port_latency / (double)instream->sample_rate;
+
     return 0;
 }
 
@@ -780,7 +797,9 @@ static int instream_end_read_jack(struct SoundIoPrivate *si, struct SoundIoInStr
 static int instream_get_latency_jack(struct SoundIoPrivate *si, struct SoundIoInStreamPrivate *is,
         double *out_latency)
 {
-    soundio_panic("TODO");
+    SoundIoInStreamJack *isj = &is->backend_data.jack;
+    *out_latency = isj->hardware_latency;
+    return 0;
 }
 
 static void notify_devices_change(SoundIoPrivate *si) {

src/jack.hpp

@@ -20,6 +20,7 @@ struct SoundIoDeviceJackPort {
     char *full_name;
     int full_name_len;
     SoundIoChannelId channel_id;
+    jack_latency_range_t latency_range;
 };
 
 struct SoundIoDeviceJack {
@@ -49,6 +50,7 @@ struct SoundIoOutStreamJack {
     int period_size;
     int frames_left;
     bool is_paused;
+    double hardware_latency;
     SoundIoOutStreamJackPort ports[SOUNDIO_MAX_CHANNELS];
     SoundIoChannelArea areas[SOUNDIO_MAX_CHANNELS];
 };
@@ -63,6 +65,7 @@ struct SoundIoInStreamJack {
     jack_client_t *client;
     int period_size;
     int frames_left;
+    double hardware_latency;
     SoundIoInStreamJackPort ports[SOUNDIO_MAX_CHANNELS];
     SoundIoChannelArea areas[SOUNDIO_MAX_CHANNELS];
     char *buf_ptrs[SOUNDIO_MAX_CHANNELS];

test/latency.cpp

@@ -53,14 +53,14 @@ static double seconds_offset = 0.0;
 
 static SoundIoRingBuffer pulse_rb;
 
-static void write_time(SoundIoOutStream *outstream) {
+static void write_time(SoundIoOutStream *outstream, double extra) {
     double latency;
     int err;
     if ((err = soundio_outstream_get_latency(outstream, &latency))) {
         soundio_panic("getting latency: %s", soundio_strerror(err));
     }
     double now = soundio_os_get_time();
-    double audible_time = now + latency;
+    double audible_time = now + latency + extra;
     double *write_ptr = (double *)soundio_ring_buffer_write_ptr(&pulse_rb);
     *write_ptr = audible_time;
     soundio_ring_buffer_advance_write_ptr(&pulse_rb, sizeof(double));
@@ -92,7 +92,7 @@ static void write_callback(struct SoundIoOutStream *outstream, int frame_count_m
             if (frames_until_pulse <= 0) {
                 if (pulse_frames_left == -1) {
                     pulse_frames_left = 0.25 * float_sample_rate;
-                    write_time(outstream); // announce beep start
+                    write_time(outstream, seconds_per_frame * frame); // announce beep start
                 }
                 if (pulse_frames_left > 0) {
                     pulse_frames_left -= 1;
@@ -101,7 +101,7 @@ static void write_callback(struct SoundIoOutStream *outstream, int frame_count_m
                     frames_until_pulse = (0.5 + (rand() / (double)RAND_MAX) * 2.0) * float_sample_rate;
                     pulse_frames_left = -1;
                     sample = 0.0;
-                    write_time(outstream); // announce beep end
+                    write_time(outstream, seconds_per_frame * frame); // announce beep end
                 }
             } else {
                 frames_until_pulse -= 1;