pcm/PcmConvert: move code to new class PcmChannelsConverter

Makefile.am

@@ -338,6 +338,7 @@ libpcm_a_SOURCES = \
 	src/pcm/PcmPack.cxx src/pcm/PcmPack.hxx \
 	src/pcm/PcmFormat.cxx src/pcm/PcmFormat.hxx \
 	src/pcm/FormatConverter.cxx src/pcm/FormatConverter.hxx \
+	src/pcm/ChannelsConverter.cxx src/pcm/ChannelsConverter.hxx \
 	src/pcm/PcmResample.cxx src/pcm/PcmResample.hxx \
 	src/pcm/PcmResampleFallback.cxx \
 	src/pcm/PcmResampleInternal.hxx \

src/pcm/ChannelsConverter.cxx

@@ -0,0 +1,115 @@
+/*
+ * 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 "ChannelsConverter.hxx"
+#include "PcmChannels.hxx"
+#include "PcmConvert.hxx"
+#include "util/ConstBuffer.hxx"
+#include "util/Error.hxx"
+
+#include <assert.h>
+
+bool
+PcmChannelsConverter::Open(SampleFormat _format,
+			   unsigned _src_channels, unsigned _dest_channels,
+			   gcc_unused Error &error)
+{
+	assert(_format != SampleFormat::UNDEFINED);
+
+	switch (_format) {
+	case SampleFormat::S16:
+	case SampleFormat::S24_P32:
+	case SampleFormat::S32:
+	case SampleFormat::FLOAT:
+		break;
+
+	default:
+		error.Format(pcm_convert_domain,
+			     "PCM channel conversion for %s is not implemented",
+			     sample_format_to_string(format));
+		return false;
+	}
+
+	format = _format;
+	src_channels = _src_channels;
+	dest_channels = _dest_channels;
+	return true;
+}
+
+void
+PcmChannelsConverter::Close()
+{
+#ifndef NDEBUG
+	format = SampleFormat::UNDEFINED;
+#endif
+}
+
+ConstBuffer<void>
+PcmChannelsConverter::Convert(ConstBuffer<void> src, Error &error)
+{
+	const void *result = nullptr;
+	size_t result_size = 0;
+
+	switch (format) {
+	case SampleFormat::UNDEFINED:
+	case SampleFormat::S8:
+	case SampleFormat::DSD:
+		assert(false);
+		gcc_unreachable();
+
+	case SampleFormat::S16:
+		result = pcm_convert_channels_16(buffer, dest_channels,
+						 src_channels,
+						 (const int16_t *)src.data,
+						 src.size, &result_size);
+		break;
+
+	case SampleFormat::S24_P32:
+		result = pcm_convert_channels_24(buffer, dest_channels,
+						 src_channels,
+						 (const int32_t *)src.data,
+						 src.size, &result_size);
+		break;
+
+	case SampleFormat::S32:
+		result = pcm_convert_channels_32(buffer, dest_channels,
+						 src_channels,
+						 (const int32_t *)src.data,
+						 src.size, &result_size);
+		break;
+
+	case SampleFormat::FLOAT:
+		result = pcm_convert_channels_float(buffer, dest_channels,
+						    src_channels,
+						    (const float *)src.data,
+						    src.size, &result_size);
+		break;
+	}
+
+	if (result == nullptr) {
+		error.Format(pcm_convert_domain,
+			     "Conversion from %u to %u channels "
+			     "is not implemented",
+			     src_channels, dest_channels);
+		return nullptr;
+	}
+
+	return { result, result_size };
+}

src/pcm/ChannelsConverter.hxx

@@ -0,0 +1,83 @@
+/*
+ * 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.
+ */
+
+#ifndef MPD_PCM_CHANNELS_CONVERTER_HXX
+#define MPD_PCM_CHANNELS_CONVERTER_HXX
+
+#include "check.h"
+#include "AudioFormat.hxx"
+#include "PcmBuffer.hxx"
+
+#ifndef NDEBUG
+#include <assert.h>
+#endif
+
+class Error;
+template<typename T> struct ConstBuffer;
+
+/**
+ * A class that converts samples from one format to another.
+ */
+class PcmChannelsConverter {
+	SampleFormat format;
+	unsigned src_channels, dest_channels;
+
+	PcmBuffer buffer;
+
+public:
+#ifndef NDEBUG
+	PcmChannelsConverter()
+		:format(SampleFormat::UNDEFINED) {}
+
+	~PcmChannelsConverter() {
+		assert(format == SampleFormat::UNDEFINED);
+	}
+#endif
+
+	/**
+	 * Opens the object, prepare for Convert().
+	 *
+	 * @param format the sample format
+	 * @param src_channels the number of source channels
+	 * @param dest_channels the number of destination channels
+	 * @param error location to store the error
+	 * @return true on success
+	 */
+	bool Open(SampleFormat format,
+		  unsigned src_channels, unsigned dest_channels,
+		  Error &error);
+
+	/**
+	 * Closes the object.  After that, you may call Open() again.
+	 */
+	void Close();
+
+	/**
+	 * Convert a block of PCM data.
+	 *
+	 * @param src the input buffer
+	 * @param error location to store the error
+	 * @return the destination buffer on success,
+	 * ConstBuffer::Null() on error
+	 */
+	gcc_pure
+	ConstBuffer<void> Convert(ConstBuffer<void> src, Error &error);
+};
+
+#endif

src/pcm/PcmConvert.cxx

@@ -19,7 +19,6 @@
 
 #include "config.h"
 #include "PcmConvert.hxx"
-#include "PcmChannels.hxx"
 #include "AudioFormat.hxx"
 #include "util/ConstBuffer.hxx"
 #include "util/Error.hxx"
@@ -72,12 +71,22 @@ PcmConvert::Open(AudioFormat _src_format, AudioFormat _dest_format,
 		return false;
 	format.format = dest_format.format;
 
+	if (format.channels != dest_format.channels &&
+	    !channels_converter.Open(format.format, format.channels,
+				     dest_format.channels, error)) {
+		format_converter.Close();
+		return false;
+	}
+
 	return true;
 }
 
 void
 PcmConvert::Close()
 {
+	if (src_format.channels != dest_format.channels)
+		channels_converter.Close();
+
 	if (src_format.format != dest_format.format)
 		format_converter.Close();
 
@@ -96,25 +105,11 @@ PcmConvert::Convert16(ConstBuffer<int16_t> src, AudioFormat format,
 {
 	assert(format.format == SampleFormat::S16);
 	assert(dest_format.format == SampleFormat::S16);
+	assert(format.channels == dest_format.channels);
 
 	auto buf = src.data;
 	size_t len = src.size * sizeof(*src.data);
 
-	if (format.channels != dest_format.channels) {
-		buf = pcm_convert_channels_16(channels_buffer,
-					      dest_format.channels,
-					      format.channels,
-					      buf, len, &len);
-		if (buf == nullptr) {
-			error.Format(pcm_convert_domain,
-				     "Conversion from %u to %u channels "
-				     "is not implemented",
-				     format.channels,
-				     dest_format.channels);
-			return nullptr;
-		}
-	}
-
 	if (format.sample_rate != dest_format.sample_rate) {
 		buf = resampler.Resample16(dest_format.channels,
 					   format.sample_rate, buf, len,
@@ -133,25 +128,11 @@ PcmConvert::Convert24(ConstBuffer<int32_t> src, AudioFormat format,
 {
 	assert(format.format == SampleFormat::S24_P32);
 	assert(dest_format.format == SampleFormat::S24_P32);
+	assert(format.channels == dest_format.channels);
 
 	auto buf = src.data;
 	size_t len = src.size * sizeof(*src.data);
 
-	if (format.channels != dest_format.channels) {
-		buf = pcm_convert_channels_24(channels_buffer,
-					      dest_format.channels,
-					      format.channels,
-					      buf, len, &len);
-		if (buf == nullptr) {
-			error.Format(pcm_convert_domain,
-				     "Conversion from %u to %u channels "
-				     "is not implemented",
-				     format.channels,
-				     dest_format.channels);
-			return nullptr;
-		}
-	}
-
 	if (format.sample_rate != dest_format.sample_rate) {
 		buf = resampler.Resample24(dest_format.channels,
 					   format.sample_rate, buf, len,
@@ -170,25 +151,11 @@ PcmConvert::Convert32(ConstBuffer<int32_t> src, AudioFormat format,
 {
 	assert(format.format == SampleFormat::S32);
 	assert(dest_format.format == SampleFormat::S32);
+	assert(format.channels == dest_format.channels);
 
 	auto buf = src.data;
 	size_t len = src.size * sizeof(*src.data);
 
-	if (format.channels != dest_format.channels) {
-		buf = pcm_convert_channels_32(channels_buffer,
-					      dest_format.channels,
-					      format.channels,
-					      buf, len, &len);
-		if (buf == nullptr) {
-			error.Format(pcm_convert_domain,
-				     "Conversion from %u to %u channels "
-				     "is not implemented",
-				     format.channels,
-				     dest_format.channels);
-			return nullptr;
-		}
-	}
-
 	if (format.sample_rate != dest_format.sample_rate) {
 		buf = resampler.Resample32(dest_format.channels,
 					   format.sample_rate, buf, len,
@@ -207,27 +174,11 @@ PcmConvert::ConvertFloat(ConstBuffer<float> src, AudioFormat format,
 {
 	assert(format.format == SampleFormat::FLOAT);
 	assert(dest_format.format == SampleFormat::FLOAT);
+	assert(format.channels == dest_format.channels);
 
 	auto buffer = src.data;
 	size_t size = src.size * sizeof(*src.data);
 
-	/* convert channels */
-
-	if (format.channels != dest_format.channels) {
-		buffer = pcm_convert_channels_float(channels_buffer,
-						    dest_format.channels,
-						    format.channels,
-						    buffer, size, &size);
-		if (buffer == nullptr) {
-			error.Format(pcm_convert_domain,
-				     "Conversion from %u to %u channels "
-				     "is not implemented",
-				     format.channels,
-				     dest_format.channels);
-			return nullptr;
-		}
-	}
-
 	/* resample with float, because this is the best format for
 	   libsamplerate */
 
@@ -274,6 +225,14 @@ PcmConvert::Convert(const void *src, size_t src_size,
 		format.format = dest_format.format;
 	}
 
+	if (format.channels != dest_format.channels) {
+		buffer = channels_converter.Convert(buffer, error);
+		if (buffer.IsNull())
+			return nullptr;
+
+		format.channels = dest_format.channels;
+	}
+
 	switch (dest_format.format) {
 	case SampleFormat::S16:
 		buffer = Convert16(ConstBuffer<int16_t>::FromVoid(buffer),

src/pcm/PcmConvert.hxx

@@ -24,6 +24,7 @@
 #include "PcmResample.hxx"
 #include "PcmBuffer.hxx"
 #include "FormatConverter.hxx"
+#include "ChannelsConverter.hxx"
 #include "AudioFormat.hxx"
 
 #include <stddef.h>
@@ -43,9 +44,7 @@ class PcmConvert {
 	PcmResampler resampler;
 
 	PcmFormatConverter format_converter;
-
+	PcmChannelsConverter channels_converter;
-	/** the buffer for converting the channel count */
-	PcmBuffer channels_buffer;
 
 	AudioFormat src_format, dest_format;