new, faster waveform generator that emphasizes gain as opposed to shape

git-svn-id: https://mlt.svn.sourceforge.net/svnroot/mlt/trunk/mlt@399 d19143bc-622f-0410-bfdd-b5b2a6649095

diff --git a/src/framework/mlt_frame.c b/src/framework/mlt_frame.c
index 46c2aaebc4c29d6eea3f0c425e7e12b42188acd7..fc67de8f2a395f18b70cf85e3ae802e4ee3f27a5 100644 (file)
--- a/src/framework/mlt_frame.c
+++ b/src/framework/mlt_frame.c
@@ -341,47 +341,51 @@ int mlt_frame_get_audio( mlt_frame this, int16_t **buffer, mlt_audio_format *for
 
 unsigned char *mlt_frame_get_waveform( mlt_frame this, double fps, int w, int h )
 {
-       /* Currently, w is not honored - the user must scale to desired height.
-          Get the integer property waveform_width after calling to see the 
-          produced width (currently equal to # samples). */
        int16_t *pcm = NULL;
        mlt_properties properties = mlt_frame_properties( this );
        mlt_audio_format format = mlt_audio_pcm;
-       int frequency = 32000; /* lower frequency available? */
+       int frequency = 32000; // lower frequency available?
        int channels = 2;
        int samples = mlt_sample_calculator( fps, frequency, mlt_frame_get_position( this ) );
        
-       /* get the pcm data */
+       // Get the pcm data
        mlt_frame_get_audio( this, &pcm, &format, &frequency, &channels, &samples );
-       mlt_properties_set_int( properties, "waveform_width", samples );
        
-       /* make an 8-bit buffer large enough to hold rendering */
-       int size = samples * h;
+       // Make an 8-bit buffer large enough to hold rendering
+       int size = w * h;
        unsigned char *bitmap = ( unsigned char* )mlt_pool_alloc( size );
        if ( bitmap != NULL )
                memset( bitmap, 0, size );
        mlt_properties_set_data( properties, "waveform", bitmap, size, ( mlt_destructor )mlt_pool_release, NULL );
        
-       /* render - pcm data has channels interleaved */
-       int vertical_resolution = h / channels;
+       // Render vertical lines
+       int16_t *ubound = pcm + samples * channels;
+       int skip = samples / w - 1;
        int i, j, k;
        
-       for ( i = 0; i < samples; i++ )
+       // Iterate sample stream and along x coordinate
+       for ( i = 0; i < w && pcm < ubound; i++ )
        {
+               // pcm data has channels interleaved
                for ( j = 0; j < channels; j++ )
                {
-                       /* the height of a "bar" is the ratio of the sample multiplied by the vertical resolution */
-                       int pcm_scaled = ( int )( ( double )( *pcm ) / 32768 * vertical_resolution / 2 );
+                       // The height of a line is the ratio of the sample multiplied by 
+                       // half the vertical resolution
+                       int pcm_scaled = ( int )( ( double )( *pcm ) / 32768 * h / 2 );
                        int height = pcm_scaled < 0 ? -pcm_scaled : pcm_scaled;
-                       int offset = j * samples * vertical_resolution;
-                       int displacement = pcm_scaled < 0 ? ( vertical_resolution / 2 ) : ( vertical_resolution / 2 - pcm_scaled );
-                       unsigned char *p = &bitmap[ offset + i + displacement * samples ];
+                       // Determine the starting y coordinate - left channel above center,
+                       // right channel below - currently assumes 2 channels
+                       int displacement = ( h / 2 ) - ( 1 - j ) * height;
+                       // Position buffer pointer using y coordinate, stride, and x coordinate
+                       unsigned char *p = &bitmap[ i + displacement * w ];
                        
+                       // Draw vertical line
                        for ( k = 0; k < height; k++ )
-                               p[ samples * k ] = 0xFF;
+                               p[ w * k ] = 0xFF;
                        
                        pcm++;
                }
+               pcm += skip * channels;
        }
 
        return bitmap;