Initial primitive audio pipeline implementation

1 files changed, 131 insertions, 0 deletions

diff --git a/audio.c b/audio.c
new file mode 100644
index 0000000..bb5ef23
--- /dev/null
+++ b/audio.c
@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2024 Mikhail Burakov. This file is part of receiver.
+ *
+ * receiver is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * receiver is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with receiver.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "audio.h"
+
+#include <alsa/asoundlib.h>
+#include <errno.h>
+#include <stdatomic.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+#include <threads.h>
+
+#include "atomic_queue.h"
+#include "toolbox/utils.h"
+
+struct AudioContext {
+  const char* device;
+  atomic_bool running;
+  struct AtomicQueue queue;
+  thrd_t thread;
+};
+
+static int AudioContextThreadProc(void* arg) {
+  struct AudioContext* context = arg;
+
+  snd_pcm_t* pcm = NULL;
+  int err = snd_pcm_open(&pcm, context->device, SND_PCM_STREAM_PLAYBACK, 0);
+  if (err) {
+    LOG("Failed to open pcm (%s)", snd_strerror(err));
+    atomic_store_explicit(&context->running, 0, memory_order_relaxed);
+    return 0;
+  }
+
+  // TODO(mburakov): Read audio configuration from the server.
+  err = snd_pcm_set_params(pcm, SND_PCM_FORMAT_S16_LE,
+                           SND_PCM_ACCESS_RW_INTERLEAVED, 2, 48000, 1, 10000);
+  if (err) {
+    LOG("Failed to set pcm params (%s)", snd_strerror(err));
+    atomic_store_explicit(&context->running, 0, memory_order_relaxed);
+    goto rollback_pcm;
+  }
+
+  while (atomic_load_explicit(&context->running, memory_order_relaxed)) {
+    // TODO(mburakov): Frame size depends on dynamic audio configuration.
+    static const unsigned frame_size = sizeof(int16_t) * 2;
+    uint8_t buffer[480 * frame_size];
+
+    size_t size = AtomicQueueRead(&context->queue, buffer, sizeof(buffer));
+    if (size < sizeof(buffer)) {
+      // LOG("Audio queue underflow!");
+      memset(buffer + size, 0, sizeof(buffer) - size);
+    }
+
+    for (snd_pcm_uframes_t offset = 0; offset < sizeof(buffer) / frame_size;) {
+      snd_pcm_sframes_t nframes =
+          snd_pcm_writei(pcm, buffer + offset * frame_size,
+                         sizeof(buffer) / frame_size - offset);
+      if (nframes < 0) {
+        LOG("Failed to write pcm (%s)", snd_strerror((int)nframes));
+        atomic_store_explicit(&context->running, 0, memory_order_relaxed);
+        goto rollback_pcm;
+      }
+      offset += (snd_pcm_uframes_t)nframes;
+    }
+  }
+
+rollback_pcm:
+  snd_pcm_close(pcm);
+  return 0;
+}
+
+struct AudioContext* AudioContextCreate(const char* device) {
+  struct AudioContext* audio_context = malloc(sizeof(struct AudioContext));
+  if (!audio_context) {
+    LOG("Failed to allocate context (%s)", strerror(errno));
+    return NULL;
+  }
+
+  audio_context->device = device;
+  atomic_init(&audio_context->running, 1);
+  if (!AtomicQueueCreate(&audio_context->queue, 4800 * sizeof(int16_t) * 2)) {
+    LOG("Failed to create queue (%s)", strerror(errno));
+    goto rollback_context;
+  }
+
+  if (thrd_create(&audio_context->thread, AudioContextThreadProc,
+                  audio_context) != thrd_success) {
+    LOG("Failed to create thread (%s)", strerror(errno));
+    goto rollback_queue;
+  }
+  return audio_context;
+
+rollback_queue:
+  AtomicQueueDestroy(&audio_context->queue);
+rollback_context:
+  free(audio_context);
+  return NULL;
+}
+
+bool AudioContextDecode(struct AudioContext* audio_context, const void* buffer,
+                        size_t size) {
+  if (!atomic_load_explicit(&audio_context->running, memory_order_relaxed)) {
+    LOG("Audio thread was stopped early!");
+    return false;
+  }
+  if (AtomicQueueWrite(&audio_context->queue, buffer, size) < size)
+    LOG("Audio queue overflow!");
+  return true;
+}
+
+void AudioContextDestroy(struct AudioContext* audio_context) {
+  atomic_store_explicit(&audio_context->running, 0, memory_order_relaxed);
+  thrd_join(audio_context->thread, NULL);
+  AtomicQueueDestroy(&audio_context->queue);
+  free(audio_context);
+}