added declicking xfade in audio_diskstream for truly seamless transport looping

[ardour.git] / libs / ardour / audio_diskstream.cc

diff --git a/libs/ardour/audio_diskstream.cc b/libs/ardour/audio_diskstream.cc
index b372c14b57d2b5927a877f003d8649dcefccd063..484e4a621a906b929cdefb829afff206ba03dd6b 100644 (file)
--- a/libs/ardour/audio_diskstream.cc
+++ b/libs/ardour/audio_diskstream.cc
@@ -1001,6 +1001,8 @@ AudioDiskstream::read (Sample* buf, Sample* mixdown_buffer, float* gain_buffer,
        nframes_t loop_start = 0;
        nframes_t loop_length = 0;
        nframes_t offset = 0;
+       nframes_t xfade_samples = 0;
+       Sample    xfade_buf[128];
        Location *loc = 0;
 
        /* XXX we don't currently play loops in reverse. not sure why */
@@ -1063,6 +1065,26 @@ AudioDiskstream::read (Sample* buf, Sample* mixdown_buffer, float* gain_buffer,
                        return -1;
                }
 
+               // xfade loop boundary if appropriate
+
+               if (xfade_samples > 0) {
+                       // just do a linear xfade for this short bit
+
+                       xfade_samples = min(xfade_samples, this_read);
+
+                       float delta = 1.0f / xfade_samples;
+                       float scale = 0.0f;
+                       Sample * tmpbuf = buf+offset;
+
+                       for (size_t i=0; i < xfade_samples; ++i) {
+                               *tmpbuf = (*tmpbuf * scale) + xfade_buf[i]*(1.0f - scale);
+                               ++tmpbuf;
+                               scale += delta; 
+                       }
+
+                       xfade_samples = 0;
+               }
+
                _read_data_count = _playlist->read_data_count();
                
                if (reversed) {
@@ -1070,13 +1092,22 @@ AudioDiskstream::read (Sample* buf, Sample* mixdown_buffer, float* gain_buffer,
                        swap_by_ptr (buf, buf + this_read - 1);
                        
                } else {
-                       
+                       start += this_read;
+               
                        /* if we read to the end of the loop, go back to the beginning */
                        
                        if (reloop) {
+                               // read crossfade samples to apply to the next read
+
+                               xfade_samples = min((nframes_t) 128, cnt-this_read);
+
+                               if (audio_playlist()->read (xfade_buf, mixdown_buffer, gain_buffer, start, xfade_samples, channel) != xfade_samples) {
+                                       error << string_compose(_("AudioDiskstream %1: cannot read xfade samples %2 from playlist at frame %3"), 
+                                                               _id, xfade_samples,start) << endmsg;
+                                       memset(xfade_buf, 0, xfade_samples * sizeof(Sample)); // just in case
+                               }
+
                                start = loop_start;
-                       } else {
-                               start += this_read;
                        }
                }