+/*****************************************************************************
+ * float32.c : precise float32 audio mixer implementation
+ *****************************************************************************
+ * Copyright (C) 2002 VideoLAN
+ * $Id: float32.c,v 1.1 2002/08/28 22:25:38 massiot Exp $
+ *
+ * Authors: Christophe Massiot <massiot@via.ecp.fr>
+ *
+ * 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., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
+ *****************************************************************************/
+
+/*****************************************************************************
+ * Preamble
+ *****************************************************************************/
+#include <errno.h>
+#include <stdlib.h> /* malloc(), free() */
+#include <string.h>
+
+#include <vlc/vlc.h>
+#include "audio_output.h"
+#include "aout_internal.h"
+
+/*****************************************************************************
+ * Local prototypes
+ *****************************************************************************/
+static int Create ( vlc_object_t * );
+
+static void DoWork ( aout_instance_t *, aout_buffer_t * );
+
+/*****************************************************************************
+ * Module descriptor
+ *****************************************************************************/
+vlc_module_begin();
+ set_description( _("float32 audio mixer module") );
+ set_capability( "audio mixer", 10 );
+ set_callbacks( Create, NULL );
+vlc_module_end();
+
+/*****************************************************************************
+ * Create: allocate trivial mixer
+ *****************************************************************************/
+static int Create( vlc_object_t *p_this )
+{
+ aout_instance_t * p_aout = (aout_instance_t *)p_this;
+
+ if ( p_aout->mixer.mixer.i_format != AOUT_FMT_FLOAT32 )
+ {
+ return -1;
+ }
+
+ if ( p_aout->i_nb_inputs == 1 )
+ {
+ /* Tell the trivial mixer to go for it. */
+ return -1;
+ }
+
+ p_aout->mixer.pf_do_work = DoWork;
+
+ return 0;
+}
+
+/*****************************************************************************
+ * ScaleWords: prepare input words for averaging
+ *****************************************************************************/
+static void ScaleWords( float * p_out, const float * p_in, size_t i_nb_words,
+ int i_nb_inputs )
+{
+ int i;
+
+ for ( i = i_nb_words; i--; )
+ {
+ *p_out++ = *p_in++ / i_nb_inputs;
+ }
+}
+
+/*****************************************************************************
+ * MeanWords: average input words
+ *****************************************************************************/
+static void MeanWords( float * p_out, const float * p_in, size_t i_nb_words,
+ int i_nb_inputs )
+{
+ int i;
+
+ for ( i = i_nb_words; i--; )
+ {
+ *p_out++ += *p_in++ / i_nb_inputs;
+ }
+}
+
+/*****************************************************************************
+ * DoWork: mix a new output buffer
+ *****************************************************************************
+ * Terminology : in this function a word designates a single float32, eg.
+ * a stereo sample is consituted of two words.
+ *****************************************************************************/
+static void DoWork( aout_instance_t * p_aout, aout_buffer_t * p_buffer )
+{
+ int i_nb_inputs = p_aout->i_nb_inputs;
+ int i_input;
+
+ for ( i_input = 0; i_input < i_nb_inputs; i_input++ )
+ {
+ int i_nb_words = p_buffer->i_nb_samples
+ * p_aout->mixer.mixer.i_channels;
+ aout_input_t * p_input = p_aout->pp_inputs[i_input];
+ float * p_out = (float *)p_buffer->p_buffer;
+ float * p_in = (float *)p_input->p_first_byte_to_mix;
+
+ for ( ; ; )
+ {
+ ptrdiff_t i_available_words = (
+ (float *)p_input->fifo.p_first->p_buffer - p_in)
+ + p_input->fifo.p_first->i_nb_samples
+ * p_aout->mixer.mixer.i_channels;
+
+ if ( i_available_words < i_nb_words )
+ {
+ aout_buffer_t * p_old_buffer;
+
+ if ( i_available_words > 0 )
+ {
+ if ( !i_input )
+ {
+ ScaleWords( p_out, p_in, i_available_words,
+ i_nb_inputs );
+ }
+ else
+ {
+ MeanWords( p_out, p_in, i_available_words,
+ i_nb_inputs );
+ }
+ }
+
+ i_nb_words -= i_available_words;
+ p_out += i_available_words;
+
+ /* Next buffer */
+ p_old_buffer = aout_FifoPop( p_aout, &p_input->fifo );
+ aout_BufferFree( p_old_buffer );
+ if ( p_input->fifo.p_first == NULL )
+ {
+ msg_Err( p_aout, "internal amix error" );
+ return;
+ }
+ p_in = (float *)p_input->fifo.p_first->p_buffer;
+ }
+ else
+ {
+ if ( i_nb_words > 0 )
+ {
+ if ( !i_input )
+ {
+ ScaleWords( p_out, p_in, i_nb_words, i_nb_inputs );
+ }
+ else
+ {
+ MeanWords( p_out, p_in, i_nb_words, i_nb_inputs );
+ }
+ }
+ p_input->p_first_byte_to_mix = (void *)(p_in
+ + i_nb_words);
+ break;
+ }
+ }
+ }
+}
+