Add a linear interpolation resampler.

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

Index: services/media/audio/platform/generic/mixers/linear_sampler.cc
diff --git a/services/media/audio/platform/generic/mixers/linear_sampler.cc b/services/media/audio/platform/generic/mixers/linear_sampler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3bb8a0bd51ef926dcda4e730be07aecdb84728c4
--- /dev/null
+++ b/services/media/audio/platform/generic/mixers/linear_sampler.cc
@@ -0,0 +1,241 @@
+// 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 "base/logging.h"
+#include "services/media/audio/platform/generic/mixers/linear_sampler.h"
+#include "services/media/audio/platform/generic/mixers/mixer_utils.h"
+
+namespace mojo {
+namespace media {
+namespace audio {
+namespace mixers {
+
+template <typename DType,
+          size_t   DChCount,
+          typename SType,
+          size_t   SChCount>
+class LinearSamplerImpl : public LinearSampler {
+ public:
+  LinearSamplerImpl()
+    : LinearSampler(FRAC_ONE - 1, FRAC_ONE - 1) {
+    Reset();
+  }
+
+  bool Mix(void*       dst,
+           uint32_t    dst_frames,
+           uint32_t*   dst_offset,
+           const void* src,
+           uint32_t    frac_src_frames,
+           int32_t*    frac_src_offset,
+           uint32_t    frac_step_size,
+           bool        accumulate) override;
+
+  void Reset() override {
+    ::memset(filter_data_, 0, sizeof(filter_data_));
+  }
+
+ private:
+  template <bool DoAccumulate>
+  inline bool Mix(void*       dst,
+                  uint32_t    dst_frames,
+                  uint32_t*   dst_offset,
+                  const void* src,
+                  uint32_t    frac_src_frames,
+                  int32_t*    frac_src_offset,
+                  uint32_t    frac_step_size);
+
+  static inline int32_t Interpolate(int32_t A, int32_t B, uint32_t alpha) {
+    return ((A * static_cast<int32_t>(FRAC_ONE - alpha))
+          + (B * static_cast<int32_t>(alpha)))
+         >> AudioTrackImpl::PTS_FRACTIONAL_BITS;
+  }
+
+  int32_t filter_data_[2 * DChCount];
+};
+
+template <typename DType,
+          size_t   DChCount,
+          typename SType,
+          size_t   SChCount>
+template <bool DoAccumulate>
+inline bool LinearSamplerImpl<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,
+    int32_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;
+  int32_t      soff = *frac_src_offset;
+
+  DCHECK_LT(doff, dst_frames);
+  DCHECK_GE(frac_src_frames, FRAC_ONE);
+  DCHECK_LE(frac_src_frames,
+            static_cast<uint32_t>(std::numeric_limits<int32_t>::max()));
+
+  if (soff < 0) {
+    DCHECK_LT(static_cast<uint32_t>(-soff), FRAC_ONE);
+
+    for (size_t D = 0; D < DChCount; ++D) {
+      filter_data_[DChCount + D] = SR::Read(src + (D / SR::DstPerSrc));
+    }
+
+    do {
+      DType* out = dst + (doff * DChCount);
+
+      for (size_t D = 0; D < DChCount; ++D) {
+        int32_t sample = Interpolate(filter_data_[DChCount + D],
+                                     filter_data_[D],
+                                     -soff);
+        out[D] = DM::Mix(out + D, sample);
+      }
+
+      doff += 1;
+      soff += frac_step_size;
+    } while ((doff < dst_frames) && (soff < 0));
+  }
+
+  int32_t source_end = static_cast<int32_t>(frac_src_frames - FRAC_ONE);
+  while ((doff < dst_frames) && (soff < source_end)) {
+    uint32_t S = (soff >> AudioTrackImpl::PTS_FRACTIONAL_BITS) * SChCount;
+    DType*   out = dst + (doff * DChCount);
+
+    for (size_t D = 0; D < DChCount; ++D) {
+      int32_t s1 = SR::Read(src + S + (D / SR::DstPerSrc));
+      int32_t s2 = SR::Read(src + S + (D / SR::DstPerSrc) + SChCount);
+      int32_t sample = Interpolate(s1, s2, soff & FRAC_MASK);
+      out[D] = DM::Mix(out + D, sample);
+    }
+
+    doff += 1;
+    soff += frac_step_size;
+  }
+
+  // If we have room to produce one more sample, and our sampling position hits
+  // the position input buffer's final frame exactly, go ahead and sample the
+  // final frame into the output buffer.
+  if ((doff < dst_frames) && (soff == source_end)) {
+    uint32_t S = (soff >> AudioTrackImpl::PTS_FRACTIONAL_BITS) * SChCount;
+    DType*   out = dst + (doff * DChCount);
+
+    for (size_t D = 0; D < DChCount; ++D) {
+      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;
+
+  if (soff >= source_end) {
+    uint32_t S = (source_end >> AudioTrackImpl::PTS_FRACTIONAL_BITS) * SChCount;
+    for (size_t D = 0; D < DChCount; ++D) {
+      filter_data_[D] = SR::Read(src + S + (D / SR::DstPerSrc));
+    }
+    return (doff < dst_frames);
+  }
+
+  return false;
+}
+
+template <typename DType,
+          size_t   DChCount,
+          typename SType,
+          size_t   SChCount>
+bool LinearSamplerImpl<DType, DChCount, SType, SChCount>::Mix(
+    void*       dst,
+    uint32_t    dst_frames,
+    uint32_t*   dst_offset,
+    const void* src,
+    uint32_t    frac_src_frames,
+    int32_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
+// Linear Sampler Mixer configurations.
+template <typename DType,
+          size_t   DChCount,
+          typename SType,
+          size_t   SChCount>
+static inline MixerPtr SelectLSM(const LpcmMediaTypeDetailsPtr& src_format,
+                                 const LpcmMediaTypeDetailsPtr& dst_format) {
+  return MixerPtr(new LinearSamplerImpl<DType, DChCount, SType, SChCount>());
+}
+
+template <typename DType,
+          size_t   DChCount,
+          typename SType>
+static inline MixerPtr SelectLSM(const LpcmMediaTypeDetailsPtr& src_format,
+                                 const LpcmMediaTypeDetailsPtr& dst_format) {
+  switch (src_format->channels) {
+  case 1:
+    return SelectLSM<DType, DChCount, SType, 1>(src_format, dst_format);
+  case 2:
+    return SelectLSM<DType, DChCount, SType, 2>(src_format, dst_format);
+  default:
+    return nullptr;
+  }
+}
+
+template <typename DType,
+          size_t   DChCount>
+static inline MixerPtr SelectLSM(const LpcmMediaTypeDetailsPtr& src_format,
+                                 const LpcmMediaTypeDetailsPtr& dst_format) {
+  switch (src_format->sample_format) {
+  case LpcmSampleFormat::UNSIGNED_8:
+    return SelectLSM<DType, DChCount, uint8_t>(src_format, dst_format);
+  case LpcmSampleFormat::SIGNED_16:
+    return SelectLSM<DType, DChCount, int16_t>(src_format, dst_format);
+  default:
+    return nullptr;
+  }
+}
+
+template <typename DType>
+static inline MixerPtr SelectLSM(const LpcmMediaTypeDetailsPtr& src_format,
+                                 const LpcmMediaTypeDetailsPtr& dst_format) {
+  switch (dst_format->channels) {
+  case 1:
+    return SelectLSM<DType, 1>(src_format, dst_format);
+  case 2:
+    return SelectLSM<DType, 2>(src_format, dst_format);
+  default:
+    return nullptr;
+  }
+}
+
+MixerPtr LinearSampler::Select(const LpcmMediaTypeDetailsPtr& src_format,
+                              const LpcmMediaTypeDetailsPtr& dst_format) {
+  switch (dst_format->sample_format) {
+  case LpcmSampleFormat::UNSIGNED_8:
+    return SelectLSM<uint8_t>(src_format, dst_format);
+  case LpcmSampleFormat::SIGNED_16:
+    return SelectLSM<int16_t>(src_format, dst_format);
+  default:
+    return nullptr;
+  }
+}
+
+}  // namespace mixers
+}  // namespace audio
+}  // namespace media
+}  // namespace mojo