1 files changed, 138 insertions, 0 deletions
diff --git a/src/CrossFade.cxx b/src/CrossFade.cxx
new file mode 100644
index 000000000..0bdcc43d6
--- /dev/null
+++ b/src/CrossFade.cxx
@@ -0,0 +1,138 @@
+/*
+ * Copyright (C) 2003-2013 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 "MusicChunk.hxx"
+#include "audio_format.h"
+#include "tag.h"
+
+#include <cmath>
+
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+#include <glib.h>
+
+#undef G_LOG_DOMAIN
+#define G_LOG_DOMAIN "crossfade"
+
+#ifdef G_OS_WIN32
+static char *
+strtok_r(char *str, const char *delim, G_GNUC_UNUSED char **saveptr)
+{
+	return strtok(str, delim);
+}
+#endif
+
+static float mixramp_interpolate(char *ramp_list, float required_db)
+{
+	float db, secs, last_db = nan(""), last_secs = 0;
+	char *ramp_str, *save_str = NULL;
+
+	/* 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 tokens out of the input string. */
+		ramp_str = strtok_r(ramp_list, " ", &save_str);
+
+		/* Tell strtok to continue next time round. */
+		ramp_list = NULL;
+
+		/* Parse the dB value. */
+		if (NULL == ramp_str) {
+			return nan("");
+		}
+		db = (float)atof(ramp_str);
+
+		/* Parse the time. */
+		ramp_str = strtok_r(NULL, ";", &save_str);
+		if (NULL == ramp_str) {
+			return nan("");
+		}
+		secs = (float)atof(ramp_str);
+
+		/* Check for exact match. */
+		if (db == required_db) {
+			return secs;
+		}
+
+		/* Save if too quiet. */
+		if (db < required_db) {
+			last_db = db;
+			last_secs = secs;
+			continue;
+		}
+
+		/* If required db < any stored value, use the least. */
+		if (std::isnan(last_db))
+			return secs;
+
+		/* Finally, interpolate linearly. */
+		secs = last_secs + (required_db - last_db) * (secs - last_secs) / (db - last_db);
+		return secs;
+	}
+}
+
+unsigned cross_fade_calc(float duration, float total_time,
+			 float mixramp_db, float mixramp_delay,
+			 float replay_gain_db, float replay_gain_prev_db,
+			 char *mixramp_start, char *mixramp_prev_end,
+			 const struct audio_format *af,
+			 const struct audio_format *old_format,
+			 unsigned max_chunks)
+{
+	unsigned int chunks = 0;
+	float chunks_f;
+	float mixramp_overlap;
+
+	if (duration < 0 || duration >= total_time ||
+	    /* we can't crossfade when the audio formats are different */
+	    !audio_format_equals(af, old_format))
+		return 0;
+
+	assert(duration >= 0);
+	assert(audio_format_valid(af));
+
+	chunks_f = (float)audio_format_time_to_size(af) / (float)CHUNK_SIZE;
+
+	if (std::isnan(mixramp_delay) || !mixramp_start || !mixramp_prev_end) {
+		chunks = (chunks_f * duration + 0.5);
+	} else {
+		/* Calculate mixramp overlap. */
+		mixramp_overlap = mixramp_interpolate(mixramp_start, mixramp_db - replay_gain_db)
+		  + mixramp_interpolate(mixramp_prev_end, mixramp_db - replay_gain_prev_db);
+		if (!std::isnan(mixramp_overlap) &&
+		    mixramp_delay <= mixramp_overlap) {
+			chunks = (chunks_f * (mixramp_overlap - mixramp_delay));
+			g_debug("will overlap %d chunks, %fs", chunks,
+				mixramp_overlap - mixramp_delay);
+		}
+	}
+
+	if (chunks > max_chunks) {
+		chunks = max_chunks;
+		g_warning("audio_buffer_size too small for computed MixRamp overlap");
+	}
+
+	return chunks;
+}