Here is some information regarding the pulse trains for the different buttons:
Vol -: 1111011101111
Vol +: 111111101111
Auto M: 11110110101111
M Cal: 1111110101111
Each pulse has a duration (frequency) of about 1.2 milliseconds. It is pulled low for approximately .4 milliseconds and high for about .8 milliseconds. Each button is represented by 13 - 15 pulses. Once the last pulse occurs, the signal stays high for 13-16 mlliseconds and then the signal repeats. The signal repeats every 29 milliseconds (regardless of which button).
Two buttons are oddballs. The Vol + button has 13 recognizable pulses and the Auto M button has 15 recognizable pulses. To me this would imply that all buttons output a code of 15 pulses (or more) but there are leading or trailing pulses that cannot be seen by the scope because they are off.