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 <framework/mlt_filter.h>
  22 #include <framework/mlt_frame.h>
  23
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26
  27 /** Get the audio.
  28 */
  29
  30 static int filter_get_audio( mlt_frame frame, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
  31 {
  32         // Get the properties of the a frame
  33         mlt_properties properties = MLT_FRAME_PROPERTIES( frame );
  34         int channels_out = mlt_properties_get_int( properties, "mono.channels" );
  35         int i, j, size;
  36         int16_t *new_buffer;
  37
  38         // Get the producer's audio
  39         mlt_frame_get_audio( frame, buffer, format, frequency, channels, samples );
  40
  41         size = *samples * channels_out * sizeof( int16_t );
  42         new_buffer = mlt_pool_alloc( size );
  43         mlt_properties_set_data( properties, "audio", new_buffer, size, ( mlt_destructor )mlt_pool_release, NULL );
  44
  45         // Mix
  46         for ( i = 0; i < *samples; i++ )
  47         {
  48                 int16_t mixdown = 0;
  49                 for ( j = 0; j < *channels; j++ )
  50                         mixdown += (*buffer)[ ( i * *channels ) + j ] / *channels;
  51                 for ( j = 0; j < channels_out; j++ )
  52                         new_buffer[ ( i * channels_out ) + j ] = mixdown;
  53         }
  54
  55         // Apply results
  56         *buffer = new_buffer;
  57         *channels = channels_out;
  58
  59         return 0;
  60 }
  61
  62 /** Filter processing.
  63 */
  64
  65 static mlt_frame filter_process( mlt_filter this, mlt_frame frame )
  66 {
  67         mlt_properties properties = MLT_FILTER_PROPERTIES( this );
  68         mlt_properties frame_props = MLT_FRAME_PROPERTIES( frame );
  69
  70         // Propogate the parameters
  71         mlt_properties_set_int( frame_props, "mono.channels", mlt_properties_get_int( properties, "channels" ) );
  72
  73         // Override the get_audio method
  74         mlt_frame_push_audio( frame, filter_get_audio );
  75
  76         return frame;
  77 }
  78
  79 /** Constructor for the filter.
  80 */
  81
  82 mlt_filter filter_mono_init( mlt_profile profile, mlt_service_type type, const char *id, char *arg )
  83 {
  84         mlt_filter this = mlt_filter_new( );
  85         if ( this != NULL )
  86         {
  87                 this->process = filter_process;
  88                 if ( arg != NULL )
  89                         mlt_properties_set_int( MLT_FILTER_PROPERTIES( this ), "channels", atoi( arg ) );
  90                 else
  91                         mlt_properties_set_int( MLT_FILTER_PROPERTIES( this ), "channels", 2 );
  92         }
  93         return this;
  94 }