2 * filter_mono.c -- mix all channels to a mono signal across n channels
3 * Copyright (C) 2003-2006 Ushodaya Enterprises Limited
4 * Author: Dan Dennedy <dan@dennedy.org>
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software Foundation,
18 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
21 #include "filter_mono.h"
23 #include <framework/mlt_frame.h>
31 static int filter_get_audio( mlt_frame frame, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
33 // Get the properties of the a frame
34 mlt_properties properties = MLT_FRAME_PROPERTIES( frame );
35 int channels_out = mlt_properties_get_int( properties, "mono.channels" );
39 // Get the producer's audio
40 mlt_frame_get_audio( frame, buffer, format, frequency, channels, samples );
42 size = *samples * channels_out * sizeof( int16_t );
43 new_buffer = mlt_pool_alloc( size );
44 mlt_properties_set_data( properties, "audio", new_buffer, size, ( mlt_destructor )mlt_pool_release, NULL );
47 for ( i = 0; i < *samples; i++ )
50 for ( j = 0; j < *channels; j++ )
51 mixdown += (*buffer)[ ( i * *channels ) + j ] / *channels;
52 for ( j = 0; j < channels_out; j++ )
53 new_buffer[ ( i * channels_out ) + j ] = mixdown;
58 *channels = channels_out;
63 /** Filter processing.
66 static mlt_frame filter_process( mlt_filter this, mlt_frame frame )
68 mlt_properties properties = MLT_FILTER_PROPERTIES( this );
69 mlt_properties frame_props = MLT_FRAME_PROPERTIES( frame );
71 // Propogate the parameters
72 mlt_properties_set_int( frame_props, "mono.channels", mlt_properties_get_int( properties, "channels" ) );
74 // Override the get_audio method
75 mlt_frame_push_audio( frame, filter_get_audio );
80 /** Constructor for the filter.
83 mlt_filter filter_mono_init( char *arg )
85 mlt_filter this = mlt_filter_new( );
88 this->process = filter_process;
90 mlt_properties_set_int( MLT_FILTER_PROPERTIES( this ), "channels", atoi( arg ) );
92 mlt_properties_set_int( MLT_FILTER_PROPERTIES( this ), "channels", 2 );