Implement audio recording for Linux via ALSA.

media/audio/linux/alsa_util.cc

+// 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.
+
+#include "media/audio/linux/alsa_util.h"
+
+#include <string>
+
+#include "base/logging.h"
+#include "media/audio/linux/alsa_wrapper.h"
+
+namespace {
+
+snd_pcm_t* OpenDevice(AlsaWrapper* wrapper,
+                      const char* device_name,
+                      snd_pcm_stream_t type,
+                      int channels,
+                      int sample_rate,
+                      snd_pcm_format_t pcm_format,
+                      int latency_us) {
+  snd_pcm_t* handle = NULL;
+  int error = wrapper->PcmOpen(&handle, device_name, type, SND_PCM_NONBLOCK);
+  if (error < 0) {
+    LOG(WARNING) << "PcmOpen: " << device_name << ","
+                 << wrapper->StrError(error);
+    return NULL;
+  }
+
+  error = wrapper->PcmSetParams(handle, pcm_format,
+                                SND_PCM_ACCESS_RW_INTERLEAVED, channels,
+                                sample_rate, 1, latency_us);
+  if (error < 0) {
+    LOG(WARNING) << "PcmSetParams: " << device_name << ", "
+                 << wrapper->StrError(error) << " - Format: " << pcm_format
+                 << " Channels: " << channels << " Latency: " << latency_us;
+    if (!alsa_util::CloseDevice(wrapper, handle)) {
+      // TODO(ajwong): Retry on certain errors?
+      LOG(WARNING) << "Unable to close audio device. Leaking handle.";
+    }
+    return NULL;
+  }
+
+  return handle;
+}
+
+}

[awong, 2010/09/02 21:16:08]

// namespace

+
+namespace alsa_util {
+
+snd_pcm_format_t BitsToFormat(int bits_per_sample) {
+  switch (bits_per_sample) {
+    case 8:
+      return SND_PCM_FORMAT_U8;
+
+    case 16:
+      return SND_PCM_FORMAT_S16;
+
+    case 24:
+      return SND_PCM_FORMAT_S24;
+
+    case 32:
+      return SND_PCM_FORMAT_S32;
+
+    default:
+      return SND_PCM_FORMAT_UNKNOWN;
+  }
+}
+
+int CloseDevice(AlsaWrapper* wrapper, snd_pcm_t* handle) {
+  std::string device_name = wrapper->PcmName(handle);
+  int error = wrapper->PcmClose(handle);
+  if (error < 0) {
+    LOG(ERROR) << "PcmClose: " << device_name << ", "
+               << wrapper->StrError(error);
+  }
+
+  return error;
+}
+
+snd_pcm_t* OpenCaptureDevice(AlsaWrapper* wrapper,
+                             const char* device_name,
+                             int channels,
+                             int sample_rate,
+                             snd_pcm_format_t pcm_format,
+                             int latency_us) {
+  return OpenDevice(wrapper, device_name, SND_PCM_STREAM_CAPTURE, channels,
+                    sample_rate, pcm_format, 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) {
+  return OpenDevice(wrapper, device_name, SND_PCM_STREAM_PLAYBACK, channels,
+                    sample_rate, pcm_format, latency_us);
+}
+
+}

[awong, 2010/09/02 21:16:08]

// namespace alsa_util

remove extra newline.

+