|実機資料||低||解決済み||修正済み||2009-02-09 03:49||2009-03-05 20:43|
boothill - ブーツヒル
|詳 細||In the discrete audio specification for Boot Hill, the filters for the left and right players' shot and hit sounds are specified as:|
DISCRETE_RCFILTER(NODE_31, 1, NODE_30, RES_K(12), CAP_U(.01)) DISCRETE_CRFILTER(BOOTHILL_L_SHOT_SND, 1, NODE_31, RES_K(12) + RES_K(68), CAP_U(.0022)) DISCRETE_RCFILTER(NODE_36, 1, NODE_35, RES_K(12), CAP_U(.01)) DISCRETE_CRFILTER(BOOTHILL_R_SHOT_SND, 1, NODE_36, RES_K(12) + RES_K(68), CAP_U(.0033)) DISCRETE_RCFILTER(NODE_41, 1, NODE_40, RES_K(12), CAP_U(.033)) DISCRETE_CRFILTER(BOOTHILL_L_HIT_SND, 1, NODE_41, RES_K(12) + RES_K(100), CAP_U(.0033)) DISCRETE_RCFILTER(NODE_46, 1, NODE_45, RES_K(12), CAP_U(.0033)) DISCRETE_CRFILTER(BOOTHILL_R_HIT_SND, 1, NODE_46, RES_K(12) + RES_K(100), CAP_U(.0022))
The component values match the schematic, but the form of the filters seems to be completely wrong. As written, the filters are composed of an RC low-pass filter followed by an RC high-pass filter (a "CR filter"), which would look like:
R1 C2 ----ZZZZ-+---------| |--+----- | | --- Z --- C1 Z R1 | | gnd Z Z R2 | gnd
The circuits on the schematic (which I have uploaded) have the form:
R1 R2 ----ZZZZ-+---------ZZZZ-+----- | | --- --- --- C1 --- C2 | | gnd gnd
This is a pair of cascaded RC low-pass filters, forming a second-order low-pass filter. Its frequency cutoff curve is steeper than that of an ordinary (first-order) RC low-pass filter.
I rebuilt MAME with the CR_FILTERs changed to RC_FILTERs fed from the existing RC_FILTERs (the second-stage RC_FILTERs only use the second resistor value, i.e., they don't add the R1 value to the resistor in the second-stage filter). Boot Hill's shot and hit sounds now seem less "tinny", since the lows aren't being filtered out and the highs are cut more strongly. The "left hit" sound (which actually happens when the right player is hit) does sound rather low in volume as well as pitch now; perhaps its filters cut its overall intensity more, or maybe this is just because I'm testing with little laptop speakers. Unfortunately I can't compare with a working machine.
Any comments are welcome.
|添付ファイル||Boot_Hill_Game_Logic_(0612-00902A).pdf (2009-02-09 03:49)|
|not_added.png (2009-03-02 08:34) |
|added.png (2009-03-02 08:34) |