Add an initial revision of an audio server.

services/media/audio/platform/generic/mixers/point_sampler.cc

Index: services/media/audio/platform/generic/mixers/point_sampler.cc
diff --git a/services/media/audio/platform/generic/mixers/point_sampler.cc b/services/media/audio/platform/generic/mixers/point_sampler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c3496785cf1215e802fce85b1fb92b3d5ca5141d
--- /dev/null
+++ b/services/media/audio/platform/generic/mixers/point_sampler.cc
@@ -0,0 +1,179 @@
+// Copyright 2015 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 <limits>
+#include <type_traits>
+
+#include "base/logging.h"
+#include "services/media/audio/audio_track_impl.h"
+#include "services/media/audio/platform/generic/mixers/mixer_utils.h"
+#include "services/media/audio/platform/generic/mixers/point_sampler.h"
+
+namespace mojo {
+namespace media {
+namespace audio {
+namespace mixers {
+
+// Point Sample Mixer implementation.
+template <typename DType,
+          size_t   DChCount,
+          typename SType,
+          size_t   SChCount>
+class PointSamplerImpl : public PointSampler {
+ public:
+  PointSamplerImpl() {}
+
+  bool Mix(void*       dst,
+           uint32_t    dst_frames,
+           uint32_t*   dst_offset,
+           const void* src,
+           uint32_t    frac_src_frames,
+           uint32_t*   frac_src_offset,
+           uint32_t    frac_step_size,
+           bool        accumulate) override;
+
+ private:
+  template <bool DoAccumulate>
+  static inline bool Mix(void*       dst,
+                         uint32_t    dst_frames,
+                         uint32_t*   dst_offset,
+                         const void* src,
+                         uint32_t    frac_src_frames,
+                         uint32_t*   frac_src_offset,
+                         uint32_t    frac_step_size);
+};
+
+template <typename DType,
+          size_t   DChCount,
+          typename SType,
+          size_t   SChCount>
+template <bool DoAccumulate>
+inline bool PointSamplerImpl<DType, DChCount, SType, SChCount>::Mix(
+    void*       dst_void,
+    uint32_t    dst_frames,
+    uint32_t*   dst_offset,
+    const void* src_void,
+    uint32_t    frac_src_frames,
+    uint32_t*   frac_src_offset,
+    uint32_t    frac_step_size) {
+  using SR = utils::SrcReader<SType, SChCount, DChCount>;
+  using DM = utils::DstMixer<DType, DoAccumulate>;
+
+  const SType* src  = static_cast<const SType*>(src_void);
+  DType*       dst  = static_cast<DType*>(dst_void);
+  uint32_t     doff = *dst_offset;
+  uint32_t     soff = *frac_src_offset;
+
+  DCHECK_LT(doff, dst_frames);
+  DCHECK_LT(soff, frac_src_frames);
+
+  while ((doff < dst_frames) && (soff < frac_src_frames)) {
+    uint32_t S = (soff >> AudioTrackImpl::PTS_FRACTIONAL_BITS) * SChCount;

[jeffbrown, 2015/11/04 23:43:34]

variables shouldn't be uppercase

[johngro, 2015/11/06 02:20:27]

Done.

+    DType*   out = dst + (doff * DChCount);
+
+    for (size_t D = 0; D < DChCount; ++D) {

[jeffbrown, 2015/11/04 23:43:34]

We could handle all of the specialization for accumulation at this level instead
of burying it down in DM::Mix.  We know the function just turns into reading
from Dest and doing an extra mix.

[johngro, 2015/11/06 02:20:27]

I disagree.  I don't want to write two versions of this loop which differ only
in whether they overwrite or accumulate and saturate.  This approach produces
the same code with no cut-n-paste.

Adding a pseudo-runtime check could avoid the duplication (something like "if
(DoAccumulate) ...") but leaves to door open for the compiler to not actually
optimize.  I realize that this is a small argument given how much we are
depending on the optimizer here, but a -O0 build might actually leave the branch
in (for no good reason).

The style here is to do everything with compile time template specialization, I
feel that this is consistent with that style.

+      int32_t sample = SR::Read(src + S + (D / SR::DstPerSrc));
+      out[D] = DM::Mix(out + D, sample);
+    }
+
+    doff += 1;
+    soff += frac_step_size;
+  }
+
+  *dst_offset = doff;
+  *frac_src_offset = soff;
+
+  return (soff >= frac_src_frames);
+}
+
+template <typename DType,
+          size_t   DChCount,
+          typename SType,
+          size_t   SChCount>
+bool PointSamplerImpl<DType, DChCount, SType, SChCount>::Mix(
+    void*       dst,
+    uint32_t    dst_frames,
+    uint32_t*   dst_offset,
+    const void* src,
+    uint32_t    frac_src_frames,
+    uint32_t*   frac_src_offset,
+    uint32_t    frac_step_size,
+    bool        accumulate) {
+  return accumulate ? Mix<true>(dst, dst_frames, dst_offset,
+                                src, frac_src_frames, frac_src_offset,
+                                frac_step_size)
+                    : Mix<false>(dst, dst_frames, dst_offset,
+                                src, frac_src_frames, frac_src_offset,
+                                frac_step_size);
+}
+
+// Templates used to expand all of the different combinations of the possible
+// Point Sampler Mixer configurations.
+template <typename DType,
+          size_t   DChCount,
+          typename SType,
+          size_t   SChCount>
+static inline MixerPtr SelectPSM(const LpcmMediaTypeDetailsPtr& src_format,
+                                 const LpcmMediaTypeDetailsPtr& dst_format) {
+  return MixerPtr(new PointSamplerImpl<DType, DChCount, SType, SChCount>());
+}
+
+template <typename DType,
+          size_t   DChCount,
+          typename SType>
+static inline MixerPtr SelectPSM(const LpcmMediaTypeDetailsPtr& src_format,
+                                 const LpcmMediaTypeDetailsPtr& dst_format) {
+  switch (src_format->samples_per_frame) {
+  case 1:
+    return SelectPSM<DType, DChCount, SType, 1>(src_format, dst_format);
+  case 2:
+    return SelectPSM<DType, DChCount, SType, 2>(src_format, dst_format);
+  default:
+    return nullptr;
+  }
+}
+
+template <typename DType,
+          size_t   DChCount>
+static inline MixerPtr SelectPSM(const LpcmMediaTypeDetailsPtr& src_format,
+                                 const LpcmMediaTypeDetailsPtr& dst_format) {
+  switch (src_format->sample_format) {
+  case LpcmSampleFormat::UNSIGNED_8:
+    return SelectPSM<DType, DChCount, uint8_t>(src_format, dst_format);
+  case LpcmSampleFormat::SIGNED_16:
+    return SelectPSM<DType, DChCount, int16_t>(src_format, dst_format);
+  default:
+    return nullptr;
+  }
+}
+
+template <typename DType>
+static inline MixerPtr SelectPSM(const LpcmMediaTypeDetailsPtr& src_format,
+                                 const LpcmMediaTypeDetailsPtr& dst_format) {
+  switch (dst_format->samples_per_frame) {
+  case 1:
+    return SelectPSM<DType, 1>(src_format, dst_format);
+  case 2:
+    return SelectPSM<DType, 2>(src_format, dst_format);
+  default:
+    return nullptr;
+  }
+}
+
+MixerPtr PointSampler::Select(const LpcmMediaTypeDetailsPtr& src_format,
+                              const LpcmMediaTypeDetailsPtr& dst_format) {
+  switch (dst_format->sample_format) {
+  case LpcmSampleFormat::UNSIGNED_8:
+    return SelectPSM<uint8_t>(src_format, dst_format);
+  case LpcmSampleFormat::SIGNED_16:
+    return SelectPSM<int16_t>(src_format, dst_format);
+  default:
+    return nullptr;
+  }
+}
+
+}  // namespace mixers
+}  // namespace audio
+}  // namespace media
+}  // namespace mojo