Clamp AudioBuffer float to int{16,32} conversion

media/base/audio_sample_conversion.h

+// Copyright 2015 The Chromium Authors. All rights reserved.

[DaleCurtis, 2016/04/01 19:31:20]

2016

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_BASE_AUDIO_SAMPLE_CONVERSION_H_
+#define MEDIA_BASE_AUDIO_SAMPLE_CONVERSION_H_
+
+#include <limits>
+
+namespace media {
+
+namespace internal {
+
+template <typename T>
+struct IntegerSampleTraits {
+  typedef T promoted_type;
+  static const T bias = 0;
+  static promoted_type min() { return std::numeric_limits<T>::min(); }
+  static promoted_type max() { return std::numeric_limits<T>::max(); }
+};
+
+template <>
+struct IntegerSampleTraits<uint8_t> {
+  typedef int16_t promoted_type;
+  static const uint8_t bias = 128;
+  static promoted_type min() { return std::numeric_limits<int8_t>::min(); }
+  static promoted_type max() { return std::numeric_limits<int8_t>::max(); }
+};
+
+}  // namespace internal
+
+template <typename Format>
+void DeinterleaveOneChannel(const Format* source,
+                            int start_frame,
+                            int frames,
+                            float* channel_data,
+                            int channel_count,
+                            int ch) {
+  using Traits = internal::IntegerSampleTraits<Format>;
+  using Promoted = typename Traits::promoted_type;
+
+  const float min = 1.0f / Traits::min();
+  const float max = 1.0f / Traits::max();
+
+  for (int i = start_frame, offset = ch; i < start_frame + frames;
+       ++i, offset += channel_count) {
+    const Promoted v = static_cast<Promoted>(source[offset]) - Traits::bias;
+    channel_data[i] = v * (v < 0 ? -min : max);

[DaleCurtis, 2016/04/01 19:31:20]

Out of curiosity if you make this "v * (v ? max : -min)" Does that change
anything?

+  }
+}
+
+template <>
+inline void DeinterleaveOneChannel<float>(const float* source,
+                                          int start_frame,
+                                          int frames,
+                                          float* channel_data,
+                                          int channel_count,
+                                          int ch) {
+  for (int i = start_frame, offset = ch; i < start_frame + frames;
+       ++i, offset += channel_count) {
+    channel_data[i] = source[offset];
+  }
+}
+
+template <typename Format>
+void InterleaveOneChannel(const float* channel_data,
+                          int start_frame,
+                          int frames,
+                          Format* dest,
+                          int channel_count,
+                          int ch) {
+  using Traits = internal::IntegerSampleTraits<Format>;
+  using Promoted = typename Traits::promoted_type;
+
+  const Promoted min = Traits::min();
+  const Promoted max = Traits::max();
+
+  for (int i = start_frame, offset = ch; i < start_frame + frames;
+       ++i, offset += channel_count) {
+    const float v = channel_data[i];
+
+    Promoted sample;
+    if (v < 0)
+      sample = v <= -1 ? min : static_cast<Promoted>(-v * min);
+    else
+      sample = v >= 1 ? max : static_cast<Promoted>(v * max);
+
+    dest[offset] = static_cast<Format>(sample + Traits::bias);
+  }
+}
+
+template <>
+inline void InterleaveOneChannel<float>(const float* channel_data,
+                                        int start_frame,
+                                        int frames,
+                                        float* dest,
+                                        int channel_count,
+                                        int ch) {
+  for (int i = start_frame, offset = ch; i < start_frame + frames;
+       ++i, offset += channel_count) {
+    dest[offset] = channel_data[i];
+  }
+}
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_SAMPLE_CONVERSION_H_