+        count = 0
+        if len(buf) % 3 == 0:            
+            # most common, divisible by 3 is likely RGB
+            LED_STRIP = ws.WS2811_STRIP_RGB
+            count = len(buf)//3
+        elif len(buf) % 4 == 0:
+            LED_STRIP = ws.SK6812_STRIP_RGBW
+            count = len(buf)//4
+        else:
+            raise RuntimeError("We only support 3 or 4 bytes-per-pixel")
+
+        ws.ws2811_channel_t_count_set(channel, count) # we manage 4 vs 3 bytes in the library