diff data/fileio/AudioFileSizeEstimator.h @ 1098:329ddaf7415d simple-fft-model

Store temporary audio files in memory if we have plenty of it

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/data/fileio/AudioFileSizeEstimator.h	Mon Jun 15 14:35:37 2015 +0100
@@ -0,0 +1,49 @@
+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    Sonic Visualiser
+    An audio file viewer and annotation editor.
+    Centre for Digital Music, Queen Mary, University of London.
+    
+    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.  See the file
+    COPYING included with this distribution for more information.
+*/
+
+#ifndef AUDIO_FILE_SIZE_ESTIMATOR_H
+#define AUDIO_FILE_SIZE_ESTIMATOR_H
+
+#include "base/BaseTypes.h"
+#include "data/fileio/FileSource.h"
+
+/**
+ * Estimate the number of samples in an audio file. For many
+ * compressed files this returns only a very approximate estimate,
+ * based on a rough estimate of compression ratio. Initially we're
+ * only aiming for a conservative estimate for purposes like "will
+ * this file fit in memory?" (and if unsure, say no).
+ */
+class AudioFileSizeEstimator
+{
+public:
+    /**
+     * Return an estimate of the number of samples (across all
+     * channels) in the given audio file, once it has been decoded and
+     * (if applicable) resampled to the given rate.
+     *
+     * This function is intended to be reasonably fast -- it may open
+     * the file, but it should not do any decoding. (However, if the
+     * file source is remote, it will probably be downloaded in its
+     * entirety before anything can be estimated.)
+     *
+     * The returned value is an estimate, and is deliberately usually
+     * on the high side. If the estimator has no idea at all, this
+     * will return 0.
+     */
+    static sv_frame_t estimate(FileSource source,
+			       sv_samplerate_t targetRate = 0);
+};
+
+#endif