pcm/PcmResampler: convert to abstract interface

The PcmResampler interface is implemented by the two classes
FallbackPcmResampler and LibsampleratePcmResampler.  This prepares for
adding more resampler libraries.

1 files changed, 74 insertions, 0 deletions

diff --git a/src/pcm/Resampler.hxx b/src/pcm/Resampler.hxx
new file mode 100644
index 000000000..a74ef4e77
--- /dev/null
+++ b/src/pcm/Resampler.hxx
@@ -0,0 +1,74 @@
+/*
+ * 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_RESAMPLER_HXX
+#define MPD_PCM_RESAMPLER_HXX
+
+#include "util/ConstBuffer.hxx"
+#include "Compiler.h"
+
+struct AudioFormat;
+class Error;
+
+/**
+ * This is an interface for plugins that convert PCM data to a
+ * specific sample rate.
+ */
+class PcmResampler {
+public:
+	virtual ~PcmResampler() {}
+
+	/**
+	 * Opens the resampler, preparing it for Resample().
+	 *
+	 * @param af the audio format of incoming data; the plugin may
+	 * modify the object to enforce another input format (however,
+	 * it may not request a different input sample rate)
+	 * @param new_sample_rate the requested output sample rate
+	 * @param error location to store the error
+	 * @return the format of outgoing data or
+	 * AudioFormat::Undefined() on error
+	 */
+	virtual AudioFormat Open(AudioFormat &af, unsigned new_sample_rate,
+				 Error &error) = 0;
+
+	/**
+	 * Closes the resampler.  After that, you may call Open()
+	 * again.
+	 */
+	virtual void Close() = 0;
+
+	/**
+	 * Resamples a block of PCM data.
+	 *
+	 * @param src the input buffer
+	 * @param src_size the size of #src_buffer in bytes
+	 * @param dest_size_r the size of the returned buffer
+	 * @param error location to store the error occurring, or nullptr
+	 * to ignore errors.
+	 * @return the destination buffer on success (will be
+	 * invalidated by filter_close() or filter_filter()), nullptr on
+	 * error
+	 */
+	gcc_pure
+	virtual ConstBuffer<void> Resample(ConstBuffer<void> src,
+					   Error &error) = 0;
+};
+
+#endif