1 files changed, 140 insertions, 0 deletions
diff --git a/src/player/CrossFade.cxx b/src/player/CrossFade.cxx
new file mode 100644
index 000000000..6d7b41440
--- /dev/null
+++ b/src/player/CrossFade.cxx
@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2003-2015 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "CrossFade.hxx"
+#include "Chrono.hxx"
+#include "MusicChunk.hxx"
+#include "AudioFormat.hxx"
+#include "util/NumberParser.hxx"
+#include "util/Domain.hxx"
+#include "Log.hxx"
+
+#include <assert.h>
+
+static constexpr Domain cross_fade_domain("cross_fade");
+
+gcc_pure
+static float
+mixramp_interpolate(const char *ramp_list, float required_db)
+{
+	float last_db = 0, last_secs = 0;
+	bool have_last = false;
+
+	/* ramp_list is a string of pairs of dBs and seconds that describe the
+	 * volume profile. Delimiters are semi-colons between pairs and spaces
+	 * between the dB and seconds of a pair.
+	 * The dB values must be monotonically increasing for this to work. */
+
+	while (1) {
+		/* Parse the dB value. */
+		char *endptr;
+		const float db = ParseFloat(ramp_list, &endptr);
+		if (endptr == ramp_list || *endptr != ' ')
+			break;
+
+		ramp_list = endptr + 1;
+
+		/* Parse the time. */
+		float secs = ParseFloat(ramp_list, &endptr);
+		if (endptr == ramp_list || (*endptr != ';' && *endptr != 0))
+			break;
+
+		ramp_list = endptr;
+		if (*ramp_list == ';')
+			++ramp_list;
+
+		/* Check for exact match. */
+		if (db == required_db) {
+			return secs;
+		}
+
+		/* Save if too quiet. */
+		if (db < required_db) {
+			last_db = db;
+			last_secs = secs;
+			have_last = true;
+			continue;
+		}
+
+		/* If required db < any stored value, use the least. */
+		if (!have_last)
+			return secs;
+
+		/* Finally, interpolate linearly. */
+		secs = last_secs + (required_db - last_db) * (secs - last_secs) / (db - last_db);
+		return secs;
+	}
+
+	return -1;
+}
+
+unsigned
+CrossFadeSettings::Calculate(SignedSongTime total_time,
+			     float replay_gain_db, float replay_gain_prev_db,
+			     const char *mixramp_start, const char *mixramp_prev_end,
+			     const AudioFormat af,
+			     const AudioFormat old_format,
+			     unsigned max_chunks) const
+{
+	unsigned int chunks = 0;
+	float chunks_f;
+
+	if (total_time.IsNegative() ||
+	    duration < 0 || duration >= total_time.ToDoubleS() ||
+	    /* we can't crossfade when the audio formats are different */
+	    af != old_format)
+		return 0;
+
+	assert(duration >= 0);
+	assert(af.IsValid());
+
+	chunks_f = (float)af.GetTimeToSize() / (float)CHUNK_SIZE;
+
+	if (mixramp_delay <= 0 || !mixramp_start || !mixramp_prev_end) {
+		chunks = (chunks_f * duration + 0.5);
+	} else {
+		/* Calculate mixramp overlap. */
+		const float mixramp_overlap_current =
+			mixramp_interpolate(mixramp_start,
+					    mixramp_db - replay_gain_db);
+		const float mixramp_overlap_prev =
+			mixramp_interpolate(mixramp_prev_end,
+					    mixramp_db - replay_gain_prev_db);
+		const float mixramp_overlap =
+			mixramp_overlap_current + mixramp_overlap_prev;
+
+		if (mixramp_overlap_current >= 0 &&
+		    mixramp_overlap_prev >= 0 &&
+		    mixramp_delay <= mixramp_overlap) {
+			chunks = (chunks_f * (mixramp_overlap - mixramp_delay));
+			FormatDebug(cross_fade_domain,
+				    "will overlap %d chunks, %fs", chunks,
+				    mixramp_overlap - mixramp_delay);
+		}
+	}
+
+	if (chunks > max_chunks) {
+		chunks = max_chunks;
+		LogWarning(cross_fade_domain,
+			   "audio_buffer_size too small for computed MixRamp overlap");
+	}
+
+	return chunks;
+}