Extract audio merging code from Player.

1 files changed, 103 insertions, 0 deletions

diff --git a/src/lib/audio_merger.h b/src/lib/audio_merger.h
new file mode 100644
index 000000000..126325a9d
--- /dev/null
+++ b/src/lib/audio_merger.h
@@ -0,0 +1,103 @@
+/*
+    Copyright (C) 2013 Carl Hetherington <cth@carlh.net>
+
+    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., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#include "audio_buffers.h"
+
+template <class T, class F>
+class AudioMerger
+{
+public:
+	AudioMerger (int channels, boost::function<F (T)> t_to_f, boost::function<T (F)> f_to_t)
+		: _buffers (new AudioBuffers (channels, 0))
+		, _next_emission (0)
+		, _t_to_f (t_to_f)
+		, _f_to_t (f_to_t)
+	{}
+
+	void push (boost::shared_ptr<const AudioBuffers> audio, T time)
+	{
+		if (time > _next_emission) {
+			/* We can emit some audio from our buffer; this is how many frames
+			   we are going to emit.
+			*/
+			F const to_emit = _t_to_f (time - _next_emission);
+			boost::shared_ptr<AudioBuffers> emit (new AudioBuffers (_buffers->channels(), to_emit));
+
+			/* And this is how many we will get from our buffer */
+			F const to_emit_from_buffers = min (to_emit, _buffers->frames ());
+
+			/* Copy the data that we have to the back end of `emit' */
+			emit->copy_from (_buffers.get(), to_emit_from_buffers, 0, to_emit - to_emit_from_buffers);
+
+			/* Silence any gap at the start */
+			emit->make_silent (0, to_emit - to_emit_from_buffers);
+
+			/* Emit that */
+			Audio (emit, _next_emission);
+
+			_next_emission += _f_to_t (to_emit);
+
+			/* And remove the data we've emitted from our buffers */
+			if (_buffers->frames() > to_emit_from_buffers) {
+				_buffers->move (to_emit_from_buffers, 0, _buffers->frames() - to_emit_from_buffers);
+			}
+			_buffers->set_frames (_buffers->frames() - to_emit_from_buffers);
+		}
+
+		/* Now accumulate the new audio into our buffers */
+		F frame = _t_to_f (time);
+		F after = max (_buffers->frames(), frame + audio->frames() - _t_to_f (_next_emission));
+		_buffers->ensure_size (after);
+		_buffers->accumulate_frames (audio.get(), 0, frame - _t_to_f (_next_emission), audio->frames ());
+		_buffers->set_frames (after);
+	}
+
+	F min (F a, int b)
+	{
+		if (a < b) {
+			return a;
+		}
+
+		return b;
+	}
+
+	F max (int a, F b)
+	{
+		if (a > b) {
+			return a;
+		}
+
+		return b;
+	}
+		
+	void flush ()
+	{
+		if (_buffers->frames() > 0) {
+			Audio (_buffers, _next_emission);
+		}
+	}
+	
+	boost::signals2::signal<void (boost::shared_ptr<const AudioBuffers>, T)> Audio;
+
+private:
+	boost::shared_ptr<AudioBuffers> _buffers;
+	T _next_emission;
+	boost::function<F (T)> _t_to_f;
+	boost::function<T (F)> _f_to_t;
+};