research.m1stereo.tv/gitweb/ - melted/blob - src/modules/core/filter_mono.c

   1 /*
   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>
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library 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 GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 #include "filter_mono.h"
  22
  23 #include <framework/mlt_frame.h>
  24
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27
  28 /** Get the audio.
  29 */
  30
  31 static int filter_get_audio( mlt_frame frame, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
  32 {
  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" );
  36         int i, j, size;
  37         int16_t *new_buffer;
  38
  39         // Get the producer's audio
  40         mlt_frame_get_audio( frame, buffer, format, frequency, channels, samples );
  41
  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 );
  45
  46         // Mix
  47         for ( i = 0; i < *samples; i++ )
  48         {
  49                 int16_t mixdown = 0;
  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;
  54         }
  55
  56         // Apply results
  57         *buffer = new_buffer;
  58         *channels = channels_out;
  59
  60         return 0;
  61 }
  62
  63 /** Filter processing.
  64 */
  65
  66 static mlt_frame filter_process( mlt_filter this, mlt_frame frame )
  67 {
  68         mlt_properties properties = MLT_FILTER_PROPERTIES( this );
  69         mlt_properties frame_props = MLT_FRAME_PROPERTIES( frame );
  70
  71         // Propogate the parameters
  72         mlt_properties_set_int( frame_props, "mono.channels", mlt_properties_get_int( properties, "channels" ) );
  73
  74         // Override the get_audio method
  75         mlt_frame_push_audio( frame, filter_get_audio );
  76
  77         return frame;
  78 }
  79
  80 /** Constructor for the filter.
  81 */
  82
  83 mlt_filter filter_mono_init( char *arg )
  84 {
  85         mlt_filter this = mlt_filter_new( );
  86         if ( this != NULL )
  87         {
  88                 this->process = filter_process;
  89                 if ( arg != NULL )
  90                         mlt_properties_set_int( MLT_FILTER_PROPERTIES( this ), "channels", atoi( arg ) );
  91                 else
  92                         mlt_properties_set_int( MLT_FILTER_PROPERTIES( this ), "channels", 2 );
  93         }
  94         return this;
  95 }