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1 files changed, 44 insertions, 0 deletions

diff --git a/lib/types.h b/lib/types.h
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+#pragma once
+#include <cstdint>
+
+/*
+ A 32.32 fixed point number.  Th*is is used for expressing fractional
+ positions in a buffer.
+
+ When used for converting from sample rate f_s to f_d, the timing
+ error at time t is bounded by t * 2^-33 * r_d / r_s.  For a
+ pessimistic conversion ratio, 8 kHz -> 192 kHz, this means that it
+ will take at least five days to accumulate one millisecond of error.
+ */
+using lfr_fixed_t = std::int64_t;
+
+
+/* ========================================
+ Sample formats
+ ======================================== */
+
+/*
+ Audio sample formats.
+ */
+enum lfr_fmt_t {
+	LFR_FMT_U8,
+	LFR_FMT_S16BE,
+	LFR_FMT_S16LE,
+	LFR_FMT_S24BE,
+	LFR_FMT_S24LE,
+	LFR_FMT_F32BE,
+	LFR_FMT_F32LE,
+	LFR_FMT_COUNT
+};
+
+
+/*
+  Specialized resampling function, designed to work with a specific
+  sample format and filter type.  Do not attempt to reuse a function
+  for a different filter.
+
+  Note that lengths are still measured in frames, but since the
+  function is specialized for a given format and number of channels,
+  there is no need to specify the format or number of channels.
+*/
+using lfr_resample_func_t = void (*)( lfr_fixed_t *pos, lfr_fixed_t inv_ratio, unsigned *dither, void *out, int outlen, const void *in, int inlen, const struct lfr_filter *filter);
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