Rework output to directly support 4A

When building for 4A, switch to new gstreamer-based ALSA output for
the RTL-SDR backend, and the Kingfisher backend now uses a gstreamer
pipeline for its loopback to either an ALSA or Pulse sink depending
on 4A or not.  Using gstreamer instead of direct ALSA output has the
benefit of transparently handling resampling to the M3ULCB hardware's
required 48 KHz sample rate for the RTL-SDR backend.

Change-Id: I2bfbf924927bb461cce88b04aba0e626f8d71215
Signed-off-by: Scott Murray <scottm@ghidorah.spiteful.org>

1 files changed, 69 insertions, 46 deletions

diff --git a/binding/radio_impl_kingfisher.c b/binding/radio_impl_kingfisher.c
index ac7ec7f..3612424 100644
--- a/binding/radio_impl_kingfisher.c
+++ b/binding/radio_impl_kingfisher.c
@@ -22,6 +22,9 @@
 #include <glib.h>
 #include <fcntl.h>
 #include <sys/stat.h>
+#include <gst/gst.h>
+#define AFB_BINDING_VERSION 2
+#include <afb/afb-binding.h>
 
 #include "radio_impl.h"
 
@@ -29,6 +32,9 @@
 #define SI_INIT	"/usr/bin/si_init"
 #define SI_CTL	"/usr/bin/si_ctl"
 
+#define GST_SINK_OPT_LEN	128
+#define GST_PIPELINE_LEN	256
+
 // Structure to describe FM band plans, all values in Hz.
 typedef struct {
 	char *name;
@@ -47,19 +53,22 @@ static fm_band_plan_t known_fm_band_plans[5] = {
 
 static unsigned int bandplan = 0;
 static bool present;
-static bool active;
 static uint32_t current_frequency;
 static int scan_valid_snr_threshold = 128;
 static int scan_valid_rssi_threshold = 128;
 static bool scanning = false;
 
+// GStreamer state
+static GstElement *pipeline;
+static bool running;
+
 static void (*freq_callback)(uint32_t, void*);
 static void *freq_callback_data;
 
 static uint32_t kf_get_min_frequency(radio_band_t band);
 static void kf_scan_stop(void);
 
-static int kf_init(void)
+static int kf_init(const char *output)
 {
 	GKeyFile* conf_file;
 	int conf_file_present = 0;
@@ -67,7 +76,8 @@ static int kf_init(void)
 	char *value_str;
 	char cmd[128];
 	int rc;
-	char *output_sink;
+	char output_sink_opt[GST_SINK_OPT_LEN];
+	char gst_pipeline_str[GST_PIPELINE_LEN];
 
 	if(present)
 		return 0;
@@ -122,7 +132,7 @@ static int kf_init(void)
 					   "scan_valid_snr_threshold",
 					   &error);
 		if(!error) {
-			fprintf(stderr, "Scan valid SNR level set to %d\n", n);
+			AFB_INFO("Scan valid SNR level set to %d", n);
 			scan_valid_snr_threshold = n;
 		}
 
@@ -132,7 +142,7 @@ static int kf_init(void)
 					   "scan_valid_rssi_threshold",
 					   &error);
 		if(!error) {
-			fprintf(stderr, "Scan valid SNR level set to %d\n", n);
+			AFB_INFO("Scan valid SNR level set to %d", n);
 			scan_valid_rssi_threshold = n;
 		}
 
@@ -141,11 +151,11 @@ static int kf_init(void)
 
 	rc = system(SI_INIT);
 	if(rc != 0) {
-		fprintf(stderr, "si_init failed, rc = %d", rc);
+		AFB_ERROR("si_init failed, rc = %d", rc);
 		return -1;
 	}
 
-	fprintf(stderr, "Using FM Bandplan: %s\n", known_fm_band_plans[bandplan].name);
+	AFB_INFO("Using FM Bandplan: %s", known_fm_band_plans[bandplan].name);
 	current_frequency = kf_get_min_frequency(BAND_FM);
 	sprintf(cmd,
 		"%s /dev/i2c-11 0x65 -b fm -p %s -t %d -u %d -c %d",
@@ -156,39 +166,50 @@ static int kf_init(void)
 		current_frequency / 1000);
 	rc = system(cmd);
 	if(rc != 0) {
-		fprintf(stderr, "%s failed, rc = %d", SI_CTL, rc);
+		AFB_ERROR("%s failed, rc = %d", SI_CTL, rc);
 		return -1;
 	}
 
-	// Handle 4A disabling PA udev module
-	if(system("pactl list sources short |grep -q alsa_input.radio") != 0) {
-		// Set up radio source
-		if(system("pactl load-module module-alsa-source device=hw:radio,0 name=radio") != 0) {
-			fprintf(stderr, "radio PA source creation failed!\n");
+	// Initialize GStreamer
+	gst_init(NULL, NULL);
+
+	if(output) {
+		AFB_INFO("Using output device %s", output);
+		rc = snprintf(output_sink_opt, GST_SINK_OPT_LEN, " device=%s", output);
+		if(rc >= GST_SINK_OPT_LEN) {
+			AFB_ERROR("output device string too long");
 			return -1;
 		}
+	} else {
+		output_sink_opt[0] = '\0';
 	}
-
-	// Set initial state to muted
-	rc = system("pactl set-source-mute alsa_input.radio 1");
-	if(rc != 0) {
-		fprintf(stderr, "pactl failed, rc = %d", rc);
+	// NOTE: If muting without pausing is desired, it can likely be done
+	//       by adding a "volume" element to the pipeline before the sink,
+	//       and setting the volume to 0 to mute.
+#ifdef HAVE_4A_FRAMEWORK
+	rc = snprintf(gst_pipeline_str,
+		      GST_PIPELINE_LEN,
+		      "alsasrc device=hw:radio ! queue ! audioconvert ! audioresample ! alsasink%s",
+		      output_sink_opt);
+#else
+	// Use PulseAudio output for compatibility with audiomanager / module_router
+	rc = snprintf(gst_pipeline_str,
+		      GST_PIPELINE_LEN,
+		      "alsasrc device=hw:radio ! queue ! audioconvert ! audioresample ! pulsesink stream-properties=\"props,media.role=radio\"");
+#endif
+	if(rc >= GST_PIPELINE_LEN) {
+		AFB_ERROR("pipeline string too long");
 		return -1;
 	}
-
-	// Set up loopback to output sink
-	output_sink = getenv("PULSE_SINK");
-	if(!output_sink) {
-		// On non-4A, loopback to the sink for the on-board Starter Kit M3/H3 audio
-		output_sink = "1";
-	}
-	sprintf(cmd, "pactl load-module module-loopback source=alsa_input.radio sink=%s", output_sink);
-	rc = system(cmd);
-	if(rc != 0) {
-		fprintf(stderr, "pactl failed, rc = %d", rc);
+	pipeline = gst_parse_launch(gst_pipeline_str, NULL);
+	if(!pipeline) {
+		AFB_ERROR("pipeline construction failed!");
 		return -1;
 	}
 
+	// Start pipeline in paused state
+	gst_element_set_state(pipeline, GST_STATE_PAUSED);
+
 	present = true;
 	return 0;
 }
@@ -281,26 +302,28 @@ static void kf_start(void)
 	if(!present)
 		return;
 
-	if(!active) {
-		rc = system("pactl set-source-mute alsa_input.radio 0");
-		if(rc != 0)
-			fprintf(stderr, "pactl set-source-mute failed!\n");
-		active = true;
+	if(!running) {
+		// Start pipeline
+		gst_element_set_state(pipeline, GST_STATE_PLAYING);
+		running = true;
 	}
 }
 
 static void kf_stop(void)
 {
-	int rc;
-
-	if(!present)
-		return;
-
-	if(active) {
-		active = false;
-		rc = system("pactl set-source-mute alsa_input.radio 1");
-		if(rc != 0)
-			fprintf(stderr, "pactl set-source-mute failed!\n");
+	GstEvent *event;
+
+	if(present && running) {
+		// Stop pipeline
+		running = false;
+		gst_element_set_state(pipeline, GST_STATE_PAUSED);
+
+		// Flush pipeline
+		// This seems required to avoid stutters on starts after a stop
+		event = gst_event_new_flush_start();
+		gst_element_send_event(GST_ELEMENT(pipeline), event);
+		event = gst_event_new_flush_stop(TRUE);
+		gst_element_send_event(GST_ELEMENT(pipeline), event); 
 	}
 }
 
@@ -324,14 +347,14 @@ static void kf_scan_start(radio_scan_direction_t direction,
 	sprintf(cmd, "%s /dev/i2c-11 0x65 -l %s", SI_CTL, direction == SCAN_FORWARD ? "up" : "down");
 	fp = popen(cmd, "r");
 	if(fp == NULL) {
-		fprintf(stderr, "Could not run: %s!\n", cmd);
+		AFB_ERROR("Could not run: %s!", cmd);
 		return;
 	}
 	// Look for "Frequency:" in output
 	while(fgets(line, 128, fp) != NULL) {
 		if(strncmp("Frequency:", line, 10) == 0) {
 			new_frequency = atoi(line + 10);
-			//fprintf(stderr, "%s: got new_frequency = %d\n", __FUNCTION__, new_frequency);
+			//AFB_DEBUG("%s: got new_frequency = %d", __FUNCTION__, new_frequency);
 			break;
 		}
 	}