2 * transition_mix.c -- mix two audio streams
3 * Copyright (C) 2003-2004 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 "transition_mix.h"
22 #include <framework/mlt_frame.h>
31 static int transition_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 a_props = mlt_frame_properties( frame );
36 // Get the b frame from the stack
37 mlt_frame b_frame = mlt_frame_pop_audio( frame );
39 // Get the properties of the b frame
40 mlt_properties b_props = mlt_frame_properties( b_frame );
42 // Restore the original get_audio
43 frame->get_audio = mlt_properties_get_data( a_props, "mix.get_audio", NULL );
45 double mix_start = 0.5, mix_end = 0.5;
46 if ( mlt_properties_get( b_props, "audio.previous_mix" ) != NULL )
47 mix_start = mlt_properties_get_double( b_props, "audio.previous_mix" );
48 if ( mlt_properties_get( b_props, "audio.mix" ) != NULL )
49 mix_end = mlt_properties_get_double( b_props, "audio.mix" );
50 if ( mlt_properties_get_int( b_props, "audio.reverse" ) )
52 mix_start = 1 - mix_start;
53 mix_end = 1 - mix_end;
55 //fprintf( stderr, "transition_mix: previous %f current %f\n", mix_start, mix_end );
57 mlt_frame_mix_audio( frame, b_frame, mix_start, mix_end, buffer, format, frequency, channels, samples );
63 /** Mix transition processing.
66 static mlt_frame transition_process( mlt_transition this, mlt_frame a_frame, mlt_frame b_frame )
68 mlt_properties properties = mlt_transition_properties( this );
69 mlt_properties b_props = mlt_frame_properties( b_frame );
71 // Only if mix is specified, otherwise a producer may set the mix
72 if ( mlt_properties_get( properties, "start" ) != NULL )
74 // Determine the time position of this frame in the transition duration
75 mlt_position in = mlt_transition_get_in( this );
76 mlt_position out = mlt_transition_get_out( this );
77 mlt_position time = mlt_frame_get_position( b_frame );
78 double mix = ( double )( time - in ) / ( double )( out - in + 1 );
80 // If there is an end mix level adjust mix to the range
81 if ( mlt_properties_get( properties, "end" ) != NULL )
83 double start = mlt_properties_get_double( properties, "start" );
84 double end = mlt_properties_get_double( properties, "end" );
85 mix = start + ( end - start ) * mix;
87 // A negative means total crossfade (uses position)
88 else if ( mlt_properties_get_double( properties, "start" ) >= 0 )
90 // Otherwise, start/constructor is a constant mix level
91 mix = mlt_properties_get_double( properties, "start" );
94 // Finally, set the mix property on the frame
95 mlt_properties_set_double( b_props, "audio.mix", mix );
97 // Initialise transition previous mix value to prevent an inadvertant jump from 0
98 if ( mlt_properties_get( properties, "previous_mix" ) == NULL )
99 mlt_properties_set_double( properties, "previous_mix", mlt_properties_get_double( b_props, "audio.mix" ) );
101 // Tell b frame what the previous mix level was
102 mlt_properties_set_double( b_props, "audio.previous_mix", mlt_properties_get_double( properties, "previous_mix" ) );
104 // Save the current mix level for the next iteration
105 mlt_properties_set_double( properties, "previous_mix", mlt_properties_get_double( b_props, "audio.mix" ) );
107 mlt_properties_set_double( b_props, "audio.reverse", mlt_properties_get_double( properties, "reverse" ) );
110 // Backup the original get_audio (it's still needed)
111 mlt_properties_set_data( mlt_frame_properties( a_frame ), "mix.get_audio", a_frame->get_audio, 0, NULL, NULL );
113 // Override the get_audio method
114 a_frame->get_audio = transition_get_audio;
116 mlt_frame_push_audio( a_frame, b_frame );
121 /** Constructor for the transition.
124 mlt_transition transition_mix_init( char *arg )
126 mlt_transition this = calloc( sizeof( struct mlt_transition_s ), 1 );
127 if ( this != NULL && mlt_transition_init( this, NULL ) == 0 )
129 this->process = transition_process;
131 mlt_properties_set_double( mlt_transition_properties( this ), "start", atof( arg ) );