daniel
4cb40f6e34
New STATIC lib + peaks_tests (CTest), mirroring bank_model. Float samples, per-channel (no fold); exact integer bin spans handle remainder, short buffers, and degenerate inputs with no OOB. Bin-span math guarded against size_t overflow for pathological binCount.
65 lines
3.0 KiB
C++
65 lines
3.0 KiB
C++
#pragma once
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// peaks — waveform min/max envelope (thumbnail) computation from raw interleaved
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// PCM. We compute our own thumbnails from the captured file rather than depending
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// on REAPER's peak API: we own the file format, so this is simpler, testable, and
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// dependency-free. A future bank panel (M5) calls this at whatever bin resolution
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// the panel width dictates and draws one min/max envelope per channel.
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//
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// PURE MODULE (CLAUDE.md §load-bearing split): NO REAPER types, NO SWELL, NO
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// vendor/ includes. Standard library only. Builds and unit-tests without REAPER.
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#include <cstddef>
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#include <vector>
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namespace reasampler {
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// Canonical in-memory sample type. `float` is REAPER's native audio buffer format
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// (its render/PCM_source callbacks hand back interleaved 32-bit float), so peaks
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// consumes that directly with no lossy conversion. If a capture ever lands as a
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// different depth, the caller converts to float at the boundary — the thumbnail
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// core stays single-typed.
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using Sample = float;
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// One bin of a channel's envelope: the extremes of every sample that fell in it.
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// min <= max always. For an empty bin (more bins than frames), both are 0.
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struct MinMax {
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Sample min = 0.0f;
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Sample max = 0.0f;
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bool operator==(const MinMax& o) const { return min == o.min && max == o.max; }
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};
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// One channel's envelope: exactly `binCount` bins, in time order.
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using ChannelEnvelope = std::vector<MinMax>;
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// Per-channel envelopes: outer index is channel (channelCount entries, order
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// preserved — never mixed or folded), inner is that channel's bins.
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using Envelope = std::vector<ChannelEnvelope>;
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// Computes a per-channel min/max envelope from interleaved PCM.
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//
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// interleaved frame-interleaved samples: [f0c0, f0c1, ..., f1c0, f1c1, ...].
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// Size must be >= frameCount * channelCount; extra is ignored.
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// channelCount channels per frame (the stride). Each channel is enveloped
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// INDEPENDENTLY — no averaging, no stereo fold (precision
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// invariant: channel count preserved).
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// frameCount frames (samples-per-channel) to consider.
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// binCount requested bins per channel. Honored exactly for any frameCount.
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//
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// Frame->bin partition: frames are split into `binCount` contiguous spans as
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// evenly as possible; when frameCount does not divide evenly, the remainder is
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// spread one-frame-per-bin across the earliest bins (ceil/floor split), so the
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// tail is never dropped and no bin reads out of bounds. When binCount > frameCount
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// the trailing empty bins are {0, 0}.
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//
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// Defined behavior for degenerate input (no UB, no throw):
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// binCount == 0 -> per channel: an empty bin vector.
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// channelCount == 0 -> an empty envelope (no channels).
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// frameCount == 0 -> per channel: binCount bins, all {0, 0}.
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Envelope computeEnvelope(const std::vector<Sample>& interleaved,
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std::size_t channelCount,
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std::size_t frameCount,
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std::size_t binCount);
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} // namespace reasampler
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