pcm/Order: new library to convert from FLAC to ALSA channel order

This new library is integrated in the PcmExport class and (if enabled)
converts MPD's channel order (= FLAC channel order) to ALSA channel
order.

This fixes:
 http://bugs.musicpd.org/view.php?id=3147
and
 http://bugs.musicpd.org/view.php?id=3255

1 files changed, 135 insertions, 0 deletions

diff --git a/src/pcm/Order.cxx b/src/pcm/Order.cxx
new file mode 100644
index 000000000..470f9d119
--- /dev/null
+++ b/src/pcm/Order.cxx
@@ -0,0 +1,135 @@
+/*
+ * 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 "Order.hxx"
+#include "PcmBuffer.hxx"
+#include "util/ConstBuffer.hxx"
+
+template<typename V>
+struct TwoPointers {
+	V *dest;
+	const V *src;
+
+	TwoPointers<V> &CopyOne() {
+		*dest++ = *src++;
+		return *this;
+	}
+
+	TwoPointers<V> &CopyTwo() {
+		return CopyOne().CopyOne();
+	}
+
+	TwoPointers<V> &SwapTwoPairs() {
+		*dest++ = src[2];
+		*dest++ = src[3];
+		*dest++ = src[0];
+		*dest++ = src[1];
+		src += 4;
+		return *this;
+	}
+
+	TwoPointers<V> &ToAlsa51() {
+		return CopyTwo() // left+right
+			.SwapTwoPairs(); // center, LFE, surround left+right
+	}
+
+	TwoPointers<V> &ToAlsa71() {
+		return ToAlsa51()
+			.CopyTwo(); // side left+right
+	}
+};
+
+template<typename V>
+static void
+ToAlsaChannelOrder51(V *dest, const V *src, size_t n)
+{
+	TwoPointers<V> p{dest, src};
+	for (size_t i = 0; i != n; ++i)
+		p.ToAlsa51();
+}
+
+template<typename V>
+static inline ConstBuffer<V>
+ToAlsaChannelOrder51(PcmBuffer &buffer, ConstBuffer<V> src)
+{
+	auto dest = buffer.GetT<V>(src.size);
+	ToAlsaChannelOrder51(dest, src.data, src.size / 6);
+	return { dest, src.size };
+}
+
+template<typename V>
+static void
+ToAlsaChannelOrder71(V *dest, const V *src, size_t n)
+{
+	TwoPointers<V> p{dest, src};
+	for (size_t i = 0; i != n; ++i)
+		p.ToAlsa71();
+}
+
+template<typename V>
+static inline ConstBuffer<V>
+ToAlsaChannelOrder71(PcmBuffer &buffer, ConstBuffer<V> src)
+{
+	auto dest = buffer.GetT<V>(src.size);
+	ToAlsaChannelOrder71(dest, src.data, src.size / 6);
+	return { dest, src.size };
+}
+
+template<typename V>
+static ConstBuffer<V>
+ToAlsaChannelOrderT(PcmBuffer &buffer, ConstBuffer<V> src, unsigned channels)
+{
+	switch (channels) {
+	case 6: // 5.1
+		return ToAlsaChannelOrder51(buffer, src);
+
+	case 8: // 7.1
+		return ToAlsaChannelOrder71(buffer, src);
+
+	default:
+		return src;
+	}
+}
+
+ConstBuffer<void>
+ToAlsaChannelOrder(PcmBuffer &buffer, ConstBuffer<void> src,
+		   SampleFormat sample_format, unsigned channels)
+{
+	switch (sample_format) {
+	case SampleFormat::UNDEFINED:
+	case SampleFormat::S8:
+	case SampleFormat::DSD:
+		return src;
+
+	case SampleFormat::S16:
+		return ToAlsaChannelOrderT(buffer,
+					   ConstBuffer<int16_t>::FromVoid(src),
+					   channels).ToVoid();
+
+	case SampleFormat::S24_P32:
+	case SampleFormat::S32:
+	case SampleFormat::FLOAT:
+		return ToAlsaChannelOrderT(buffer,
+					   ConstBuffer<int32_t>::FromVoid(src),
+					   channels).ToVoid();
+	}
+
+	gcc_unreachable();
+}