diff trunk/matlab/bmm/carfac/SAI_StabilizeLayer.m @ 619:2e456754fe20

Better functionization of SAI, and new way to make picture with lag
marginal and smoothed history of lag marginal.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/trunk/matlab/bmm/carfac/SAI_StabilizeLayer.m	Mon May 13 21:15:56 2013 +0000
@@ -0,0 +1,55 @@
+function layer_struct = SAI_StabilizeLayer(layer_struct)
+% Pick trigger points in buffer, shift rows to offset_from_end,
+% and blend into frame
+
+frame = layer_struct.frame;
+
+nap_buffer = real(layer_struct.nap_buffer);
+n_buffer_times = size(nap_buffer, 1);
+[n_ch, width] = size(frame);
+
+% Make the window to use for all the channels at this layer.
+window_size = layer_struct.window_width;
+n_window_pos = layer_struct.n_window_pos;
+% Windows are always (approx) 50% overlapped:
+d_win = window_size / 2;
+
+after_samples = layer_struct.future_lags;
+
+window_range = (1:window_size) + ...
+  (n_buffer_times - window_size) - after_samples - ...
+  floor((n_window_pos - 1) * d_win);
+window = sin((1:window_size)' * pi / window_size);
+% This should not go negative!
+offset_range = (1:width) + ...
+  (n_buffer_times - width - window_size) - floor((n_window_pos - 1) * d_win);
+% CHECK
+if any(offset_range < 0)
+  error;
+end
+
+% smooth across channels; more in later layers
+smoothed_buffer =  smooth1d(nap_buffer', layer_struct.channel_smoothing_scale)';
+
+% For each buffer column (channel), pick a trigger and align into SAI_frame
+for ch = 1:n_ch
+  smooth_wave = smoothed_buffer(:, ch);  % for the trigger
+  
+  % Do several window positions and triggers
+  for w = 1:n_window_pos
+    % move the window to later and go aggain
+    [peak_val, trigger_time] = max(smooth_wave(window_range + ...
+      floor((w - 1) * d_win)) .* window);
+    nap_wave = nap_buffer(:, ch);  % for the waveform
+    if peak_val <= 0  % just use window center instead
+      [peak_val, trigger_time] = max(window);
+    end
+    % TODO(dicklyon):  alpha blend here.
+    trigger_time = trigger_time + floor((w - 1) * d_win);
+    alpha = (0.025 + peak_val) / (0.5 + peak_val);  % alpha 0.05 to near 1.0
+    frame(ch, :) = alpha * nap_wave(trigger_time + offset_range)' + ...
+      (1 - alpha) * frame(ch, :);
+  end
+end
+
+layer_struct.frame = frame;