From 1b175025fecb1c10e6719d4ab79c188d473fccc4 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@duempel.org>
Date: Thu, 31 Jan 2013 20:33:26 +0100
Subject: pcm_*: convert to C++

---
 src/PcmDither.cxx | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 src/PcmDither.cxx

(limited to 'src/PcmDither.cxx')

diff --git a/src/PcmDither.cxx b/src/PcmDither.cxx
new file mode 100644
index 00000000..e1811908
--- /dev/null
+++ b/src/PcmDither.cxx
@@ -0,0 +1,93 @@
+/*
+ * 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 "PcmDither.hxx"
+#include "PcmPrng.hxx"
+
+static int16_t
+pcm_dither_sample_24_to_16(int32_t sample, struct pcm_dither *dither)
+{
+	int32_t output, rnd;
+
+	enum {
+		from_bits = 24,
+		to_bits = 16,
+		scale_bits = from_bits - to_bits,
+		round = 1 << (scale_bits - 1),
+		mask = (1 << scale_bits) - 1,
+		ONE = 1 << (from_bits - 1),
+		MIN = -ONE,
+		MAX = ONE - 1
+	};
+
+	sample += dither->error[0] - dither->error[1] + dither->error[2];
+
+	dither->error[2] = dither->error[1];
+	dither->error[1] = dither->error[0] / 2;
+
+	/* round */
+	output = sample + round;
+
+	rnd = pcm_prng(dither->random);
+	output += (rnd & mask) - (dither->random & mask);
+
+	dither->random = rnd;
+
+	/* clip */
+	if (output > MAX) {
+		output = MAX;
+
+		if (sample > MAX)
+			sample = MAX;
+	} else if (output < MIN) {
+		output = MIN;
+
+		if (sample < MIN)
+			sample = MIN;
+	}
+
+	output &= ~mask;
+
+	dither->error[0] = sample - output;
+
+	return (int16_t)(output >> scale_bits);
+}
+
+void
+pcm_dither_24_to_16(struct pcm_dither *dither,
+		    int16_t *dest, const int32_t *src, const int32_t *src_end)
+{
+	while (src < src_end)
+		*dest++ = pcm_dither_sample_24_to_16(*src++, dither);
+}
+
+static int16_t
+pcm_dither_sample_32_to_16(int32_t sample, struct pcm_dither *dither)
+{
+	return pcm_dither_sample_24_to_16(sample >> 8, dither);
+}
+
+void
+pcm_dither_32_to_16(struct pcm_dither *dither,
+		    int16_t *dest, const int32_t *src, const int32_t *src_end)
+{
+	while (src < src_end)
+		*dest++ = pcm_dither_sample_32_to_16(*src++, dither);
+}
-- 
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