Implement audio recording for Linux via ALSA.

media/audio/linux/alsa_util.h

Index: media/audio/linux/alsa_util.h
diff --git a/media/audio/linux/alsa_util.h b/media/audio/linux/alsa_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..5c9a0a04dc4c1cc2378fbd15074be98003c75a73
--- /dev/null
+++ b/media/audio/linux/alsa_util.h
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+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_AUDIO_LINUX_ALSA_UTIL_H_
+#define MEDIA_AUDIO_LINUX_ALSA_UTIL_H_
+
+#include <alsa/asoundlib.h>
+
+class AlsaWrapper;
+
+namespace alsa_util {
+
+snd_pcm_format_t BitsToFormat(int bits_per_sample);
+
+snd_pcm_t* OpenCaptureDevice(AlsaWrapper* wrapper,
+                             const char* device_name,
+                             int channels,
+                             int sample_rate,
+                             snd_pcm_format_t pcm_format,
+                             int latency_us);
+
+snd_pcm_t* OpenPlaybackDevice(AlsaWrapper* wrapper,
+                              const char* device_name,
+                              int channels,
+                              int sample_rate,
+                              snd_pcm_format_t pcm_format,
+                              int latency_us);
+
+int CloseDevice(AlsaWrapper* wrapper, snd_pcm_t* handle);
+
+}
+
+#endif  // MEDIA_AUDIO_LINUX_ALSA_UTIL_H_