Class: MIDI::IO::SeqWriter
- Inherits:
-
Object
- Object
- MIDI::IO::SeqWriter
- Defined in:
- lib/midilib/io/seqwriter.rb
Instance Method Summary collapse
-
#initialize(seq, proc = nil) ⇒ SeqWriter
constructor
:yields: num_tracks, index.
-
#possibly_munge_due_to_running_status_byte(data, prev_status) ⇒ Object
If we can use a running status byte, delete the status byte from the given data.
- #write16(val) ⇒ Object
- #write32(val) ⇒ Object
- #write_bytes(bytes) ⇒ Object
- #write_header ⇒ Object
- #write_instrument(instrument) ⇒ Object
-
#write_to(io) ⇒ Object
Writes a MIDI format 1 file.
- #write_track(track) ⇒ Object
- #write_var_len(val) ⇒ Object
Constructor Details
#initialize(seq, proc = nil) ⇒ SeqWriter
:yields: num_tracks, index
12 13 14 15 |
# File 'lib/midilib/io/seqwriter.rb', line 12 def initialize(seq, proc = nil) # :yields: num_tracks, index @seq = seq @update_block = block_given?() ? Proc.new() : proc end |
Instance Method Details
#possibly_munge_due_to_running_status_byte(data, prev_status) ⇒ Object
If we can use a running status byte, delete the status byte from the given data. Return the status to remember for next time as the running status byte for this event.
79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 |
# File 'lib/midilib/io/seqwriter.rb', line 79 def possibly_munge_due_to_running_status_byte(data, prev_status) status = data[0] return status if status >= 0xf0 || prev_status >= 0xf0 chan = (status & 0x0f) return status if chan != (prev_status & 0x0f) status = (status & 0xf0) prev_status = (prev_status & 0xf0) # Both events are on the same channel. If the two status bytes are # exactly the same, the rest is trivial. If it's note on/note off, # we can combine those further. if status == prev_status data[0,1] = [] # delete status byte from data return status + chan elsif status == NOTE_OFF && data[2] == 64 # If we see a note off and the velocity is 64, we can store # a note on with a velocity of 0. If the velocity isn't 64 # then storing a note on would be bad because the would be # changed to 64 when reading the file back in. data[2] = 0 # set vel to 0; do before possible shrinking status = NOTE_ON + chan if prev_status == NOTE_ON data[0,1] = [] # delete status byte else data[0] = status end return status else # Can't compress data return status + chan end end |
#write16(val) ⇒ Object
126 127 128 129 130 131 132 133 |
# File 'lib/midilib/io/seqwriter.rb', line 126 def write16(val) val = (-val | 0x8000) if val < 0 buffer = [] @io.putc((val >> 8) & 0xff) @io.putc(val & 0xff) @bytes_written += 2 end |
#write32(val) ⇒ Object
135 136 137 138 139 140 141 142 143 |
# File 'lib/midilib/io/seqwriter.rb', line 135 def write32(val) val = (-val | 0x80000000) if val < 0 @io.putc((val >> 24) & 0xff) @io.putc((val >> 16) & 0xff) @io.putc((val >> 8) & 0xff) @io.putc(val & 0xff) @bytes_written += 4 end |
#write_bytes(bytes) ⇒ Object
145 146 147 148 |
# File 'lib/midilib/io/seqwriter.rb', line 145 def write_bytes(bytes) bytes.each { |b| @io.putc(b) } bytes.length end |
#write_header ⇒ Object
29 30 31 32 33 34 35 |
# File 'lib/midilib/io/seqwriter.rb', line 29 def write_header @io.print 'MThd' write32(6) write16(1) # Ignore sequence format; write as format 1 write16(@seq.tracks.length) write16(@seq.ppqn) end |
#write_instrument(instrument) ⇒ Object
114 115 116 117 118 119 |
# File 'lib/midilib/io/seqwriter.rb', line 114 def write_instrument(instrument) event = MetaEvent.new(META_INSTRUMENT, instrument) write_var_len(0) data = event.data_as_bytes() @bytes_written += write_bytes(data) end |
#write_to(io) ⇒ Object
Writes a MIDI format 1 file.
18 19 20 21 22 23 24 25 26 27 |
# File 'lib/midilib/io/seqwriter.rb', line 18 def write_to(io) @io = io @bytes_written = 0 write_header() @update_block.call(nil, @seq.tracks.length, 0) if @update_block @seq.tracks.each_with_index do |track, i| write_track(track) @update_block.call(track, @seq.tracks.length, i) if @update_block end end |
#write_track(track) ⇒ Object
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 |
# File 'lib/midilib/io/seqwriter.rb', line 37 def write_track(track) @io.print 'MTrk' track_size_file_pos = @io.tell() write32(0) # Dummy byte count; overwritten later @bytes_written = 0 # Reset after previous write write_instrument(track.instrument) prev_event = nil prev_status = 0 track.events.each do |event| if !event.kind_of?(Realtime) write_var_len(event.delta_time) end data = event.data_as_bytes() status = data[0] # status byte plus channel number, if any # running status byte status = possibly_munge_due_to_running_status_byte(data, prev_status) @bytes_written += write_bytes(data) prev_event = event prev_status = status end # Write track end event. event = MetaEvent.new(META_TRACK_END) write_var_len(0) @bytes_written += write_bytes(event.data_as_bytes()) # Go back to beginning of track data and write number of bytes, # then come back here to end of file. @io.seek(track_size_file_pos) write32(@bytes_written) @io.seek(0, ::IO::SEEK_END) end |
#write_var_len(val) ⇒ Object
121 122 123 124 |
# File 'lib/midilib/io/seqwriter.rb', line 121 def write_var_len(val) buffer = Utils.as_var_len(val) @bytes_written += write_bytes(buffer) end |