Implemented circular buffer mode in linux output stream driver.

openrtx/include/interfaces/audio_stream.h

@@ -106,6 +106,7 @@ void inputStream_stop(streamId id);
  * @param prio: priority of the requester.
  * @param buf: buffer containing the audio samples.
  * @param length: length of the buffer, in elements.
+ * @param mode: operation mode of the buffer
  * @param sampleRate: sample rate in Hz.
  * @return a unique identifier for the stream or -1 if the stream could not be
  * opened.
@@ -138,7 +139,7 @@ stream_sample_t *outputStream_getIdleBuffer(const streamId id);
  * synchronisation point, the function returns immediately.
  *
  * @param id: stream identifier.
- * @param bufChanged: if true, notifies the strem handler that new data has
+ * @param bufChanged: if true, notifies the stream handler that new data has
  * been written to the idle section of the data buffer. This field is valid
  * only in circular double buffered mode.
  * @return true if execution was effectively blocked, false if stream is not

platform/drivers/audio/outputStream_linux.c

@@ -22,23 +22,62 @@
 #include <interfaces/audio_stream.h>
 #include <pulse/error.h>
 #include <pulse/simple.h>
+#include <pulse/pulseaudio.h>
 #include <stddef.h>
 #include <stdio.h>
 
+// Expand opaque pa_simple struct
+struct pa_simple {
+    pa_threaded_mainloop *mainloop;
+    pa_context *context;
+    pa_stream *stream;
+    pa_stream_direction_t direction;
+
+    const void *read_data;
+    size_t read_index, read_length;
+
+    int operation_success;
+};
+
 static int           priority          = PRIO_BEEP; // Current priority
 static bool          running           = false;     // Stream is running
-pa_simple *s = NULL;                    // Pulseaudio instance
+static pa_simple     *p                = NULL;      // Pulseaudio instance
-int error;                              // Error code
+static int           error             = 0;         // Error code
+static enum BufMode  buf_mode;                      // Buffer operation mode
+static stream_sample_t *buf            = NULL;      // Playback buffer
+static size_t        buf_len           = 0;         // Buffer length
+static bool          first_half_active = true; // Circular addressing mode flag
+
+static void buf_circ_write_cb(pa_stream *s, size_t length, void *userdata)
+{
+    (void) userdata;
+    // TODO: We can play length more bytes of data
+    // Start playback of the other half
+    stream_sample_t *active_buf = (first_half_active) ?
+        buf : buf + buf_len / 2;
+    first_half_active = !first_half_active;
+    size_t active_buf_len = buf_len / 2;
+
+    if (!s || length <= 0)
+        return;
+
+    if (pa_stream_begin_write(s, (void **) &active_buf, &active_buf_len) < 0)
+    {
+        fprintf(stderr, "pa_stream_begin_write() failed: %s", pa_strerror(pa_context_errno(p->context)));
+        return;
+    }
+
+    pa_stream_write(s, active_buf, active_buf_len, NULL, 0, PA_SEEK_RELATIVE);
+}
 
 streamId outputStream_start(const enum AudioSink destination,
                             const enum AudioPriority prio,
-                            stream_sample_t * const buf,
+                            stream_sample_t * const buffer,
                             const size_t length,
                             const enum BufMode mode,
                             const uint32_t sampleRate)
 {
     assert(destination == SINK_SPK && "Only speaker sink was implemented!\n");
-    assert(mode == BUF_LINEAR && "Only linear buffering was implemented!\n");
 
     /* The Sample format to use */
     static pa_sample_spec ss = {
@@ -60,28 +99,34 @@ streamId outputStream_start(const enum AudioSink destination,
     // Assign priority and set stream as running
     priority = prio;
     running  = true;
+    buf_mode = mode;
+    buf = buffer;
+    buf_len = length;
+    first_half_active = true;
 
-    if (!s)
+    if (!p)
-    {
-        if (!(s = pa_simple_new(NULL,
-                                "OpenRTX",
-                                PA_STREAM_PLAYBACK,
-                                NULL,
-                                "playback",
-                                &ss,
-                                NULL,
-                                NULL,
-                                &error)))
     {
+        // Create a new playback stream
+        if (!(p = pa_simple_new(NULL, "OpenRTX", PA_STREAM_PLAYBACK, NULL, "Audio out", &ss, NULL, NULL, &error))) {
             fprintf(stderr, __FILE__": pa_simple_new() failed: %s\n", pa_strerror(error));
             return -1;
         }
     }
 
-    if (pa_simple_write(s, buf, length, &error) < 0) {
+    if (mode == BUF_LINEAR)
+    {
+        if (pa_simple_write(p, buf, length, &error) < 0) {
             fprintf(stderr, __FILE__": pa_simple_write() failed: %s\n", pa_strerror(error));
             return -1;
         }
+    }
+    else if (mode == BUF_CIRC_DOUBLE)
+    {
+        assert(p->stream && "Invalid PulseAudio Stream!");
+
+        // Register write callback
+        pa_stream_set_write_callback(p->stream, buf_circ_write_cb, NULL);
+    }
 
     return 0;
 }
@@ -90,6 +135,12 @@ stream_sample_t *outputStream_getIdleBuffer(const streamId id)
 {
     (void) id;
 
+    if (buf_mode == BUF_CIRC_DOUBLE)
+    {
+        // Return half of the buffer not currently being read
+        return (!first_half_active) ? buf : buf + buf_len / 2;
+    }
+    else
         return NULL;
 }
 
@@ -99,7 +150,7 @@ bool outputStream_sync(const streamId id, const bool bufChanged)
     (void) bufChanged;
 
     /* Make sure that every single sample was played */
-    if (pa_simple_drain(s, &error) < 0) {
+    if (pa_simple_drain(p, &error) < 0) {
         fprintf(stderr, __FILE__": pa_simple_drain() failed: %s\n", pa_strerror(error));
         return false;
     }
@@ -114,7 +165,7 @@ void outputStream_stop(const streamId id)
     (void) id;
 
     /* Make sure that every single sample was played */
-    if (pa_simple_flush(s, &error) < 0) {
+    if (pa_simple_flush(p, &error) < 0) {
         fprintf(stderr, __FILE__": pa_simple_drain() failed: %s\n", pa_strerror(error));
     }
 
@@ -125,6 +176,6 @@ void outputStream_terminate(const streamId id)
 {
     (void) id;
 
-    if (s)
+    if (p)
-        pa_simple_free(s);
+        pa_simple_free(p);
 }