作者vivimice (麥斯◎我的奶酪在哪裡﹖)
看板Visual_Basic
標題[API] The Channel Map
時間Wed Jul 27 15:17:05 2005
來源﹕mk:@MSITStore:E:\Microsoft%20Visual%20Studio\MSDN98\98VS\2052\
MultiMed.chm::/devdoc/live/pdgrmm/images/mmap_a05.gif
翻譯﹕vivimice 智慧權所有
原載﹕縹緲水雲間 (bbs.freecity.cn)
The Channel Map
The channel map affects all MIDI channel messages. MIDI channel messages
include note-on, note-off, polyphonic-key-aftertouch, control-change,
program-change, channel-aftertouch, and pitch-bend-change messages. The
MIDI Mapper uses a single channel map with an entry for each of the 16 MIDI
channels. Each channel-map entry specifies the following:
‧A destination channel for the MIDI message
‧A destination output device for the MIDI message
‧An optional patch map specifying other possible modifications for the
MIDI message
The destination channel is set to one of the 16 MIDI channels. MIDI messages
are modified to reflect each new channel assignment. For example, if the
destination channel entry for MIDI channel 4 is set to 6, all MIDI messages
sent to channel 4 will be mapped to channel 6, as shown in the following
illustration.
┌────────┐
│ MIDI Mapper │
├────────┤
0x93, 0x60, 0x7F →│ Channel Mapper │→ 0x95, 0x60, 0x7F
﹉﹉﹉﹉﹉﹉﹉﹉ └────────┘ ﹉﹉﹉﹉﹉﹉﹉﹉
Value Value
Before Mapping After Mapping
In this example, the MIDI status byte 0x93 is mapped to 0x95. The low-order
of a MIDI status byte specifies the channel number. Source channels are set
to either active or inactive. Messages sent to inactive source channels are
ignored, so an inactive channel is in effect muted or turned off.
The destination output device is set to one of the available MIDI output
devices. A MIDI output device can be an internal synthesizer or a physical
MIDI output port.
MIDI system messages are MIDI messages (with status bytes) from 0xF0 to 0xFF.
There is no channel associated with MIDI system messages, so they cannot be
mapped. MIDI system messages are sent to all MIDI output devices listed in a
channel map.
參考譯文﹕
通道表影響所有的MIDI通道消息。MIDI通道消息包含音符開啟、音符關閉、復音鍵觸後
響應、控制器變更、程序碼變更、通道觸後響應和彎音輪消息。MIDI映射表使用帶有對
應於16個MIDI通道的16個入口的單個MIDI映射表。每個入口指定一下信息﹕
‧MIDI消息的目標通道
‧MIDI消息的目標輸出設備
‧一個可選的樂器表﹐該樂器表指定了對MIDI消息的其它可能的變更。
目標通道被設置為16個MIDI通道之一﹐MIDI消息被變更以便於重定向到每個新分配的通
道。例如﹐如果4號MIDI通道的目標通道入口被設置為6的話﹐那麼所有送往4號通道的
都會被映射到6號通道﹐如圖所示。（見上圖）
在這個例子中﹐MIDI狀態字節0x93被映射成為0x95。MIDI狀態字節的低位（譯者注﹕準
確地說應該是低四位）指定了通道號碼。源通道被設置成為活動的或者非活動的。送往
非活動狀態源通道的消息將會被忽略掉﹐所以非活動狀態通道在效果上相當於被靜音的
或者被關閉的通道。
目標輸出設備設置成可用的MIDI輸出設備。一個MIDI輸出設備可以是一個內部的合成器
或者一個物理MIDI輸出端口。
MIDI系統消息是指標志位為0xF0～0xFF的MIDI消息。系統消息是沒有對應的通道與之相
聯系的﹐所以它們不能被映射。MIDI系統消息會被送往通道列表中列出的所有MIDI輸出
設備。
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