Use the libspeexdsp resampler

AFAICT it runs a little slower? but it's fixed point, and has much
better understood audio characteristics.

1 files changed, 18 insertions, 17 deletions

diff --git a/src/codecs/include/sample.hpp b/src/codecs/include/sample.hpp
index f8e08cdc..ea3a7ffc 100644
--- a/src/codecs/include/sample.hpp
+++ b/src/codecs/include/sample.hpp
@@ -9,38 +9,43 @@
 namespace sample {
 
 // A signed, 32-bit PCM sample.
-typedef int32_t Sample;
+typedef int16_t Sample;
 
 constexpr auto Clip(int64_t v) -> Sample {
-  if (v > INT32_MAX)
-    return INT32_MAX;
-  if (v < INT32_MIN)
-    return INT32_MIN;
+  if (v > INT16_MAX)
+    return INT16_MAX;
+  if (v < INT16_MIN)
+    return INT16_MIN;
   return v;
 }
 
 constexpr auto FromSigned(int32_t src, uint_fast8_t bits) -> Sample {
-  // Left-align samples, effectively scaling them up to 32 bits.
-  return src << (sizeof(Sample) * 8 - bits);
+  if (bits > 16) {
+    // Left-align samples, effectively scaling them up to 32 bits.
+    return src << (sizeof(Sample) * 8 - bits);
+  } else if (bits < 16) {
+    return src << (bits - (sizeof(Sample) * 8));
+  }
+  return src;
 }
 
 constexpr auto FromUnsigned(uint32_t src, uint_fast8_t bits) -> Sample {
   // Left-align, then substract the max value / 2 to make the sample centred
   // around zero.
-  return (src << (sizeof(uint32_t) * 8 - bits)) - (~0UL >> 1);
+  return (src << (sizeof(uint16_t) * 8 - bits)) - (~0UL >> 1);
 }
 
 constexpr auto FromFloat(float src) -> Sample {
-  return std::clamp<float>(src, -1.0f, 1.0f) * static_cast<float>(INT32_MAX);
+  return std::clamp<float>(src, -1.0f, 1.0f) * static_cast<float>(INT16_MAX);
 }
 
 constexpr auto FromDouble(double src) -> Sample {
-  return std::clamp<double>(src, -1.0, 1.0) * static_cast<double>(INT32_MAX);
+  return std::clamp<double>(src, -1.0, 1.0) * static_cast<double>(INT16_MAX);
 }
 
 constexpr auto FromMad(mad_fixed_t src) -> Sample {
   // Round the bottom bits.
-  src += (1L << (MAD_F_FRACBITS - 24));
+  src += (1L << (MAD_F_FRACBITS - 16));
 
   // Clip the leftover bits to within range.
   if (src >= MAD_F_ONE)
@@ -49,14 +54,10 @@ constexpr auto FromMad(mad_fixed_t src) -> Sample {
     src = -MAD_F_ONE;
 
   // Quantize.
-  return FromSigned(src >> (MAD_F_FRACBITS + 1 - 24), 24);
+  return FromSigned(src >> (MAD_F_FRACBITS + 1 - 16), 16);
 }
 
-constexpr auto ToSigned16Bit(Sample src) -> int16_t {
-  return src >> 16;
-}
-
-static constexpr float kFactor = 1.0f / static_cast<float>(INT32_MAX);
+static constexpr float kFactor = 1.0f / static_cast<float>(INT16_MAX);
 
 constexpr auto ToFloat(Sample src) -> float {
   return src * kFactor;