rick_2047
12/20/2008 7:47:00 AM
Ok i was going through the book "Ruby practical Projects" and right at
the first chapter i had this problem. The first chapter is all about
calling the alsa raw midi functions in ruby to play midi from ruby. I
think i did everything right but still i get no sound. I debuged my
project but at the lines when the function call is made nothing
happens, there is not even an error. Can anybody give me any pointers
to what should i do. Here is my code ..
1 require 'dl/import'
2
3 class LiveMIDI
4 ON = 0x90
5 OFF = 0x80
6 PC = 0xC0
7
8 def initialize
9 open
10 end
11
12 def note_on(channel, note, velocity=64)
13 message(ON | channel, note, velocity)
14 end
15
16 def note_off(channel, note, velocity=64)
17 message(OFF | channel, note, velocity)
18 end
19
20 def program_change(channel, preset)
21 message(PC | channel, preset)
22 end
23 end
24
25 if RUBY_PLATFORM.include?('mswin')
26 class LiveMIDI
27 # Windows code here
28 module C
29 extend DL::Importable
30 dlload 'winmm'
31
32
33 extern "int midiOutOpen(HMIDIOUT*, int,
int, int, int)"
34 extern "int midiOutClose(int)"
35 extern "int midiOutShortMsg(int, int)"
36 end
37 def open
38 @device = DL.malloc(DL.sizeof('I'))
39 C.midiOutOpen(@device, -1, 0, 0, 0)
40 end
41 def close
42 C.midiOutClose(@device.ptr.to_i)
43 end
44 def message(one, two=0, three=0)
45 message = one + (two << 8) + (three << 16)
46 C.midiOutShortMsg(@device.ptr.to_i,
message)
47 end
48 end
49
50 elsif RUBY_PLATFORM.include?('darwin')
51 class LiveMIDI
52 # Mac code here
53 end
54 elsif RUBY_PLATFORM.include?('linux')
55 class LiveMIDI
56 module C
57 extend DL::Importable
58 dlload '/usr/lib/libasound.so.2.0.0'
59
60
61 extern "int snd_rawmidi_open(void*, void*,
char*, int)"
62 extern "int snd_rawmidi_close(void*)"
63 extern "int snd_rawmidi_write(void*,
void*, int)"
64 extern "int snd_rawmidi_drain(void*)"
65 end
66
67 def open
68 @output = DL::PtrData.new(nil)
69 C.snd_rawmidi_open(nil,
@output.ref,"virtual",0)
70 end
71
72 def close
73 C.snd_rawmidi_close(@output)
74 end
75
76 def message(*args)
77 format= "C" * args.size
78 bytes = args.pack(format).to_ptr
79 C.snd_rawmidi_write(@output, bytes,
args.size)
80 C.snd_rawmidi_drain(@output)
81 end
82 end
83 else
84 raise "Couldn't find a LiveMIDI implementation for your
platform"
85 end
86
87
88 #require 'music'
89 midi = LiveMIDI.new
90 sleep(8)
91 midi.note_on(0,60,100)
92 sleep(1)
93 midi.note_off(0,60)
94 sleep(1)
95 midi.program_change(1,40)
96 midi.note_on(1,60,100)
97 sleep(1)
98 midi.note_off(1,60)
99 puts "done"
of course you could skip the windows part coz i never tested it
anyways.