Motown in-proc streaming framework used to implement media services.

services/media/framework/lpcm_util.cc

+// Copyright 2016 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 "base/logging.h"
+#include "services/media/framework/lpcm_util.h"
+#include "services/media/framework/ostream.h"
+
+namespace mojo {
+namespace media {
+
+LpcmUtil* LpcmUtil::Create(const LpcmStreamType& stream_type) {
+  switch (stream_type.sample_format()) {
+    case LpcmStreamType::SampleFormat::kUnsigned8:
+    case LpcmStreamType::SampleFormat::kAny:
+      return new LpcmUtilImpl<uint8_t>(stream_type);
+    case LpcmStreamType::SampleFormat::kSigned16:
+      return new LpcmUtilImpl<int16_t>(stream_type);
+    case LpcmStreamType::SampleFormat::kSigned24In32:
+      return new LpcmUtilImpl<int32_t>(stream_type);
+    case LpcmStreamType::SampleFormat::kFloat:
+      return new LpcmUtilImpl<float>(stream_type);
+    default:
+      NOTREACHED()
+          << "unsupported sample format " << stream_type.sample_format();
+      return nullptr;
+  }
+}
+
+template<typename T>
+LpcmUtilImpl<T>::LpcmUtilImpl(const LpcmStreamType& stream_type) :
+    stream_type_(stream_type) {}
+
+template<typename T>
+LpcmUtilImpl<T>::~LpcmUtilImpl() {}
+
+template<typename T>
+void LpcmUtilImpl<T>::Silence(void* buffer, uint64_t frame_count) const {

[johngro, 2016/01/25 18:55:43]

for the cases of filling a non-float, signed buffer with zeros or filling a
uint8_t buffer with 0x80, ::memset is probably a better option than a for loop
as the environment's std library implementation of memset can pull some nice
tricks for speed's sake.

float and multibyte unisgned int types probably still need a for loop.

Depending on how much typing you want to do, you could use type traits to
separate out the memset version and the for loop versions (the memset version
should run if T is uint8_t or if T is a signed integral type)

[dalesat, 2016/01/25 23:29:37]

Done.

+  T* sample = reinterpret_cast<T*>(buffer);
+  for (
+      uint64_t sample_countdown = frame_count * stream_type_.channels();
+      sample_countdown != 0;
+      --sample_countdown) {
+    *sample = 0;
+    sample++;
+  }
+}
+
+template<>
+void LpcmUtilImpl<uint8_t>::Silence(void* buffer, uint64_t frame_count) const {
+  uint8_t* sample = reinterpret_cast<uint8_t*>(buffer);
+  for (
+      uint64_t sample_countdown = frame_count * stream_type_.channels();
+      sample_countdown != 0;
+      --sample_countdown) {
+    *sample = 0x80;
+    sample++;
+  }
+}
+
+template<typename T>
+void LpcmUtilImpl<T>::Copy(void* in, void* out, uint64_t frame_count) const {
+  std::memcpy(out, in, stream_type_.min_buffer_size(frame_count));
+}
+
+template<typename T>
+void LpcmUtilImpl<T>::Mix(void* in, void* out, uint64_t frame_count) const {
+  T* in_sample = reinterpret_cast<T*>(in);
+  T* out_sample = reinterpret_cast<T*>(out);
+  for (
+      uint64_t sample_countdown = frame_count * stream_type_.channels();
+      sample_countdown != 0;
+      --sample_countdown) {
+    *out_sample += *in_sample; // TODO(dalesat): Limit.
+    out_sample++;
+    in_sample++;
+  }
+}
+
+template<>
+void LpcmUtilImpl<uint8_t>::Mix(void* in, void* out, uint64_t frame_count)
+    const {
+  uint8_t* in_sample = reinterpret_cast<uint8_t*>(in);
+  uint8_t* out_sample = reinterpret_cast<uint8_t*>(out);
+  for (
+      uint64_t sample_countdown = frame_count * stream_type_.channels();
+      sample_countdown != 0;
+      --sample_countdown) {
+    *out_sample = uint8_t(uint16_t(*out_sample) + uint16_t(*in_sample) - 0x80);
+    // TODO(dalesat): Limit.
+    out_sample++;
+    in_sample++;
+  }
+}
+
+template<typename T>
+void LpcmUtilImpl<T>::Interleave(
+    void* in,
+    uint64_t in_byte_count,
+    void* out,
+    uint64_t frame_count) const {
+  DCHECK(in);
+  DCHECK(in_byte_count);
+  DCHECK(out);
+  DCHECK(frame_count);
+
+  uint32_t channels = stream_type_.channels();
+  uint64_t in_channel_stride = in_byte_count / channels;

[johngro, 2016/01/25 18:55:43]

see comment in header re: in_byte_count.  That said, if we are keeping
in_byte_count, then we should ASSERT both channels and !(in_byte_count %
channels)

[dalesat, 2016/01/25 23:29:37]

Done.

+
+  uint8_t* in_channel = reinterpret_cast<uint8_t*>(in);
+  uint8_t* out_channel = reinterpret_cast<uint8_t*>(out);
+
+  for (uint32_t channel = channels; channel != 0; --channel) {
+    T* in_sample = reinterpret_cast<T*>(in_channel);
+    T* out_sample = reinterpret_cast<T*>(out_channel);
+    for (uint64_t frame = frame_count; frame != 0; --frame) {
+      *out_sample = *in_sample;
+      ++in_sample;
+      out_sample += channels;
+    }
+    in_channel += in_channel_stride;
+    out_channel += stream_type_.sample_size();
+  }
+}
+
+}  // namespace media
+}  // namespace mojo