145 lines
4.2 KiB
C++
145 lines
4.2 KiB
C++
/*
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* Copyright 2003-2020 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "CrossFade.hxx"
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#include "Chrono.hxx"
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#include "MusicChunk.hxx"
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#include "pcm/AudioFormat.hxx"
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#include "util/NumberParser.hxx"
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#include "util/Domain.hxx"
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#include "util/Math.hxx"
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#include "Log.hxx"
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#include <cassert>
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static constexpr Domain cross_fade_domain("cross_fade");
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gcc_pure
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static FloatDuration
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mixramp_interpolate(const char *ramp_list, float required_db) noexcept
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{
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float last_db = 0;
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FloatDuration last_duration = FloatDuration::zero();
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bool have_last = false;
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/* ramp_list is a string of pairs of dBs and seconds that describe the
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* volume profile. Delimiters are semi-colons between pairs and spaces
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* between the dB and seconds of a pair.
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* The dB values must be monotonically increasing for this to work. */
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while (true) {
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/* Parse the dB value. */
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char *endptr;
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const float db = ParseFloat(ramp_list, &endptr);
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if (endptr == ramp_list || *endptr != ' ')
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break;
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ramp_list = endptr + 1;
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/* Parse the time. */
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FloatDuration duration{ParseFloat(ramp_list, &endptr)};
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if (endptr == ramp_list || (*endptr != ';' && *endptr != 0))
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break;
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ramp_list = endptr;
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if (*ramp_list == ';')
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++ramp_list;
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/* Check for exact match. */
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if (db == required_db) {
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return duration;
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}
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/* Save if too quiet. */
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if (db < required_db) {
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last_db = db;
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last_duration = duration;
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have_last = true;
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continue;
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}
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/* If required db < any stored value, use the least. */
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if (!have_last)
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return duration;
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/* Finally, interpolate linearly. */
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duration = last_duration + (required_db - last_db) * (duration - last_duration) / (db - last_db);
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return duration;
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}
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return FloatDuration(-1);
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}
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unsigned
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CrossFadeSettings::Calculate(SignedSongTime total_time,
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float replay_gain_db, float replay_gain_prev_db,
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const char *mixramp_start, const char *mixramp_prev_end,
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const AudioFormat af,
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const AudioFormat old_format,
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unsigned max_chunks) const noexcept
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{
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unsigned int chunks = 0;
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if (total_time.IsNegative() ||
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duration <= FloatDuration::zero() ||
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duration >= std::chrono::duration_cast<FloatDuration>(total_time) ||
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/* we can't crossfade when the audio formats are different */
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af != old_format)
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return 0;
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assert(duration > FloatDuration::zero());
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assert(af.IsValid());
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const auto chunk_duration =
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af.SizeToTime<FloatDuration>(sizeof(MusicChunk::data));
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if (mixramp_delay <= FloatDuration::zero() ||
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!mixramp_start || !mixramp_prev_end) {
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chunks = lround(duration / chunk_duration);
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} else {
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/* Calculate mixramp overlap. */
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const auto mixramp_overlap_current =
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mixramp_interpolate(mixramp_start,
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mixramp_db - replay_gain_db);
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const auto mixramp_overlap_prev =
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mixramp_interpolate(mixramp_prev_end,
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mixramp_db - replay_gain_prev_db);
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const auto mixramp_overlap =
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mixramp_overlap_current + mixramp_overlap_prev;
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if (mixramp_overlap_current >= FloatDuration::zero() &&
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mixramp_overlap_prev >= FloatDuration::zero() &&
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mixramp_delay <= mixramp_overlap) {
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chunks = lround((mixramp_overlap - mixramp_delay)
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/ chunk_duration);
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FormatDebug(cross_fade_domain,
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"will overlap %d chunks, %fs", chunks,
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(mixramp_overlap - mixramp_delay).count());
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}
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}
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if (chunks > max_chunks) {
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chunks = max_chunks;
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LogWarning(cross_fade_domain,
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"audio_buffer_size too small for computed MixRamp overlap");
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}
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return chunks;
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}
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