CSNG (File Format): Difference between revisions

CSNG (File Format) (view source)

35 bytes removed , 16 August 2018

Clarify nature of delta time encoding

Anonymous user

@@ Line 150: / Line 150: @@
 Just like MIDI, each command starts with a '''delta time''' value telling the sequencer
-how many ticks to wait after the previous command. Unlike MIDI, Factor5 uses a custom
+how many ticks to wait after the previous command. Unlike MIDI, Factor5 uses a fixed 16-bit
-[[wikipedia:Run-length encoding|RLE scheme]] to adaptively scale the value's precision
+value to store the delta times. In case of a delta time greater than 65535, no-op commands
-to reduce the value's size.
+with a 65535 delta time are inserted into the command stream until the target time is attained.
-The RLE operates on 16-bit words, with the value 0xffff triggering a continuation,
+In a theoretical Python streaming API, the delta time can be decoded with no-ops automatically consumed like so:
-then a 'dead' 16-bit word skipped over, then the 0xffff is summed with the following RLE value,
-looping the decode algorithm.
-In Python, decoding works like so:
 <syntaxhighlight lang="python" line="1">
-def DecodeDeltaTimeRLE(streamIn):
+def DecodeDeltaTime(streamIn):
      total = 0
      while True:
          term = streamIn.ReadU16()
-         if term == 0xffff:
+        next = streamIn.PeekU16()
+         if next == 0:
              total += 0xffff
-             dummy = streamIn.ReadU16()
+             streamIn.seekAhead(2)
              continue
          total += term