| カテゴリ | 重要度 | ステータス | 解決状況 | 登録日時 | 最終更新 |
|---|---|---|---|---|---|
 サウンド | 低 | 仮承認 | 未処理 | 2013-08-12 05:27 | 2013-08-14 00:32 |
| テスター | Ace | 担当者 | ソース | ||
| バージョン | 0.149 | 発生バージョン | 修正バージョン | ||
| 修正コミット | プルリク | ||||
| フラグ | バグかもね | ||||
| セット | All sets using SegaPCM | ||||
| セット詳細 | |||||
| 概 要 | SegaPCMによるPCM出力が実機と違う。フィルタリングのせいかどうかは不明。 | ||||
| 詳 細 | I've been looking through some videos of a few Sega games using the SegaPCM chip, more specifically Galaxy Force II and After Burner II, and noticed the SegaPCM audio is noticeably different from what it sounds like in MAME. I have two videos here taken from the original boards of each of these games (not my videos): Galaxy Force II (audio is a bit distorted in this video): After Burner II (there are times where the audio gets severely garbled - also, be sure to only click the Play button once otherwise you will be redirected to NicoNico): http://nicoviewer.net/sm20566807 However, I'm not sure whether the issue has to do with filtering or inaccuracies in the SegaPCM emulation, hence why I noted this bug as "possible." I have found schematics of Galaxy Force here (After Burner II uses the same audio setup, so the audio section of the schematic also applies to After Burner II. I did find a schematic for that game, but the scan is of really poor quality and the audio circuit is illegible): http://tamdb.net/G/Galaxy%20Force%20Schematics.pdf Page 9 shows the audio circuit on the right side of the page. Looking at the audio circuit, there's an active low-pass filter with a cutoff frequency of 32883.25Hz followed by a passive high-pass filter with a cutoff frequency of 0.07Hz. That does not alter the audio in any perceivable way. Then, there's the After Burner owner's manual: http://dweeb.net/afterburner/owners_manual/afterburner_owners_manual.pdf Page 25 has a wiring diagram of all the major electronic components in the cabinet, and there's an extra amplifier board labeled 839-0035-01/PWR AMP BD between the audio out of the X-Board and the speakers. Other Sega games have this board as well like OutRun (not sure about Galaxy Force). Going by these, the audio differences here could be either caused by that board or emulation issues with the SegaPCM chip (I don't have any schematics of the 839-0035-01, so I don't know if it applies any extra filtering or not). If the audio differences do turn out to be caused by filtering on the 839-0035-01 board, please disregard this bug report. EDIT: Apparently, I missed something in the audio circuit. There are two MF6CN-50 chips (IC114 and IC118 respectively) after the AD7520 DAC hooked up to the Sega PCM chip and those are 6th-order switched Butterworth low-pass filters. Okay, my mistake, I thought there was actually something wrong with the Sega PCM emulation, but it's not the source of the problem. Please disregard. | ||||
| 再現手順 | |||||
| 追加情報 | As I don't have access to any games using the SegaPCM chip (yet, I will have to speak to the owner of a local arcade shop about getting any X-Board, Y-Board, etc. games for a few days to verify this), an audio sample taken straight from the SegaPCM chip before being mixed with the YM2151 would be of great help. | ||||
| 添付ファイル | |||||