From adbd1f070dc93b71d0191e42746720d06df64e93 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niccol=C3=B2=20Izzo?= <izzo.niccolo@gmail.com>
Date: Sat, 23 Jul 2022 17:27:32 +0200
Subject: [PATCH] Fixed bug in circular buffer management inside linux output
 stream driver, added unit test for circular buffer mode.

TG-220
---
 platform/drivers/audio/outputStream_linux.c | 46 +++++++++++++------
 tests/unit/play_sine.c                      | 50 ++++++++++++++++++---
 2 files changed, 78 insertions(+), 18 deletions(-)

diff --git a/platform/drivers/audio/outputStream_linux.c b/platform/drivers/audio/outputStream_linux.c
index b7c3b3f5..5efc857b 100644
--- a/platform/drivers/audio/outputStream_linux.c
+++ b/platform/drivers/audio/outputStream_linux.c
@@ -47,27 +47,38 @@ 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 size_t        offset            = 0;         // Playback offset
 
 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;
+    size_t remaining = 0;
 
     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;
-    }
+    if (offset >= buf_len / 2)
+        first_half_active = false;
 
-    pa_stream_write(s, active_buf, active_buf_len, NULL, 0, PA_SEEK_RELATIVE);
+    remaining = buf_len - offset;
+
+    // We can play all the rest of the buffer
+    if (length > remaining)
+    {
+        pa_stream_write(s, buf + offset, remaining, NULL, 0, PA_SEEK_RELATIVE);
+
+        if(first_half_active == true)
+            first_half_active = false;
+        else
+            first_half_active = true;
+
+        offset = 0;
+    }
+    else
+    {
+        pa_stream_write(s, buf + offset, length, NULL, 0, PA_SEEK_RELATIVE);
+        offset += length;
+    }
 }
 
 streamId outputStream_start(const enum AudioSink destination,
@@ -124,6 +135,12 @@ streamId outputStream_start(const enum AudioSink destination,
     {
         assert(p->stream && "Invalid PulseAudio Stream!");
 
+        if (pa_simple_write(p, buf, length / 2, &error) < 0) {
+            fprintf(stderr, __FILE__": pa_simple_write() failed: %s\n", pa_strerror(error));
+            return -1;
+        }
+        offset = length / 2;
+
         // Register write callback
         pa_stream_set_write_callback(p->stream, buf_circ_write_cb, NULL);
     }
@@ -155,7 +172,10 @@ bool outputStream_sync(const streamId id, const bool bufChanged)
         return false;
     }
 
-    running = false;
+    if (buf_mode == BUF_LINEAR)
+    {
+        running = false;
+    }
 
     return true;
 }
diff --git a/tests/unit/play_sine.c b/tests/unit/play_sine.c
index 9c581094..d745d670 100644
--- a/tests/unit/play_sine.c
+++ b/tests/unit/play_sine.c
@@ -24,6 +24,7 @@
 
 #include <interfaces/audio_stream.h>
 #include <math.h>
+#include <stdio.h>
 
 #define BUF_LEN 4096 * 10
 #define AMPLITUDE 20000
@@ -37,16 +38,21 @@
 
 int16_t buffer[BUF_LEN] = { 0 };
 
-int main()
+void fill_buffer_sine(int16_t *buffer, size_t len)
 {
-    int id = 0;
-
-    // Create 440 Hz sine wave
-    for(int i = 0; i < BUF_LEN; i++)
+    for(size_t i = 0; i < len; i++)
     {
         buffer[i] = AMPLITUDE * sin(2 * PI * i *
                     ((float) FREQUENCY / SAMPLE_RATE));
     }
+}
+
+void play_sine_linear()
+{
+    int id = 0;
+
+    // Create 440 Hz sine wave
+    fill_buffer_sine(buffer, BUF_LEN);
 
     // Play back sine wave
     for(int i = 0; i < 10; i++)
@@ -64,3 +70,37 @@ int main()
     outputStream_stop(id);
     outputStream_terminate(id);
 }
+
+void play_sine_circular()
+{
+    int id = 0;
+    stream_sample_t *buf = NULL;
+
+    // Fill first half of buffer with sine
+    fill_buffer_sine(buffer, BUF_LEN / 2);
+
+    // Play back sine wave
+    id = outputStream_start(SINK_SPK,
+                            PRIO_PROMPT,
+                            buffer,
+                            BUF_LEN,
+                            BUF_CIRC_DOUBLE,
+                            SAMPLE_RATE);
+
+    for(int i = 0; i < 10; i++)
+    {
+        buf = outputStream_getIdleBuffer(id);
+        fill_buffer_sine(buf, BUF_LEN / 2);
+        outputStream_sync(id, true);
+    }
+
+    // Sync, flush, terminate
+    outputStream_stop(id);
+    outputStream_terminate(id);
+}
+
+int main()
+{
+    //play_sine_linear();
+    play_sine_circular();
+}