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◆ main openmsx / src / sound / ResampleBlip.cc
3.5 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
e8555c89 Andy McCall 1 
#include "ResampleBlip.hh"
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#include "ResampledSoundDevice.hh"
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#include "narrow.hh"
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#include "one_of.hh"
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#include "small_buffer.hh"
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#include "xrange.hh"
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#include <algorithm>
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#include <array>
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#include <cassert>
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namespace openmsx {
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template<unsigned CHANNELS>
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ResampleBlip<CHANNELS>::ResampleBlip(
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		ResampledSoundDevice& input_, const DynamicClock& hostClock_)
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	: ResampleAlgo(input_)
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	, hostClock(hostClock_)
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	, step([&]{ // calculate 'hostClock.getFreq() / getEmuClock().getFreq()', but with less rounding errors
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			uint64_t emuPeriod = input_.getEmuClock().getPeriod().toUint64(); // unknown units
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			uint64_t hostPeriod = hostClock.getPeriod().toUint64(); // unknown units, but same as above
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			return FP::roundRatioDown(narrow<unsigned>(emuPeriod),
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			                          narrow<unsigned>(hostPeriod));
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		}())
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{
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	std::ranges::fill(lastInput, 0.0f);
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}
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template<unsigned CHANNELS>
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bool ResampleBlip<CHANNELS>::generateOutputImpl(float* dataOut, size_t hostNum,
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                                                EmuTime time)
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{
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	auto& emuClk = getEmuClock();
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	if (unsigned emuNum = emuClk.getTicksTill(time); emuNum > 0) {
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		// 3 extra for padding, CHANNELS extra for sentinel
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		// Clang will produce a link error if the length expression is put
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		// inside the macro.
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		const unsigned len = emuNum * CHANNELS + std::max(3u, CHANNELS);
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		small_buffer<float, 8192> buf(uninitialized_tag{}, len); // typical ~5194 (PSG, samples=1024) but could be larger
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		EmuTime emu1 = emuClk.getFastAdd(1); // time of 1st emu-sample
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		assert(emu1 > hostClock.getTime());
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		if (input.generateInput(buf.data(), emuNum)) {
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			FP pos1;
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			hostClock.getTicksTill(emu1, pos1);
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			for (auto ch : xrange(CHANNELS)) {
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				// In case of PSG (and to a lesser degree SCC) it happens
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				// very often that two consecutive samples have the same
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				// value. We can benefit from this by setting a sentinel
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				// at the end of the buffer and move the end-of-loop test
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				// into the 'samples differ' branch.
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				assert(emuNum > 0);
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				buf[CHANNELS * emuNum + ch] =
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					buf[CHANNELS * (emuNum - 1) + ch] + 1.0f;
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				FP pos = pos1;
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				auto last = lastInput[ch]; // local var is slightly faster
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				for (unsigned i = 0; /**/; ++i) {
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					if (auto delta = buf[CHANNELS * i + ch] - last;
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					    delta != 0) [[unlikely]] {
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						if (i == emuNum) {
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							break;
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						}
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						last = buf[CHANNELS * i + ch];
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						blip[ch].addDelta(
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							BlipBuffer::TimeIndex(pos),
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							delta);
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					}
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					pos += step;
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				}
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				lastInput[ch] = last;
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			}
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		} else {
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			// input all zero
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			BlipBuffer::TimeIndex pos;
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			hostClock.getTicksTill(emu1, pos);
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			for (auto ch : xrange(CHANNELS)) {
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				if (lastInput[ch] != 0.0f) {
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					auto delta = -lastInput[ch];
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					lastInput[ch] = 0.0f;
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					blip[ch].addDelta(pos, delta);
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				}
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			}
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		}
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		emuClk += emuNum;
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	}
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	std::array<bool, CHANNELS> results;
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	for (auto ch : xrange(CHANNELS)) {
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		results[ch] = blip[ch].template readSamples<CHANNELS>(dataOut + ch, hostNum);
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	}
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	static_assert(CHANNELS == one_of(1u, 2u), "either mono or stereo");
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	if constexpr (CHANNELS == 1) {
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		return results[0];
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	} else {
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		if (results[0] == results[1]) {
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			// Both muted or both unmuted
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			return results[0];
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		} else {
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			// One channel muted, the other not.
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			// We have to set the muted channel to all-zero.
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			unsigned offset = results[0] ? 1 : 0;
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			for (auto i : xrange(hostNum)) {
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				dataOut[2 * i + offset] = 0.0f;
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			}
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			return true;
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		}
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	}
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}
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// Force template instantiation.
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template class ResampleBlip<1>;
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template class ResampleBlip<2>;
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} // namespace openmsx