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/*
Copyright (C) 2012 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 <stdint.h>
#include <cstring>
#include <algorithm>
#include <iostream>
#include "delay_line.h"
#include "util.h"
using std::min;
using boost::shared_ptr;
/** @param channels Number of channels of audio.
* @param frames Delay in frames, +ve to move audio later.
*/
DelayLine::DelayLine (shared_ptr<Log> log, int channels, int frames)
: AudioProcessor (log)
, _negative_delay_remaining (0)
, _frames (frames)
{
if (_frames > 0) {
/* We need a buffer to keep some data in */
_buffers.reset (new AudioBuffers (channels, _frames));
_buffers->make_silent ();
} else if (_frames < 0) {
/* We can do -ve delays just by chopping off
the start, so no buffer needed.
*/
_negative_delay_remaining = -_frames;
}
}
void
DelayLine::process_audio (shared_ptr<AudioBuffers> data)
{
if (_buffers) {
/* We have some buffers, so we are moving the audio later */
/* Copy the input data */
AudioBuffers input (*data.get ());
int to_do = data->frames ();
/* Write some of our buffer to the output */
int const from_buffer = min (to_do, _buffers->frames());
data->copy_from (_buffers.get(), from_buffer, 0, 0);
to_do -= from_buffer;
/* Write some of the input to the output */
int const from_input = to_do;
data->copy_from (&input, from_input, 0, from_buffer);
int const left_in_buffer = _buffers->frames() - from_buffer;
/* Shuffle our buffer down */
_buffers->move (from_buffer, 0, left_in_buffer);
/* Copy remaining input data to our buffer */
_buffers->copy_from (&input, input.frames() - from_input, from_input, left_in_buffer);
} else {
/* Chop the initial data off until _negative_delay_remaining
is zero, then just pass data.
*/
int const to_do = min (data->frames(), _negative_delay_remaining);
if (to_do) {
data->move (to_do, 0, data->frames() - to_do);
data->set_frames (data->frames() - to_do);
_negative_delay_remaining -= to_do;
}
}
Audio (data);
}
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