Difference between revisions of "User:Buddha^/GSoC2007-ProjectDiary"

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Revision as of 09:28, 30 July 2007

1,487 bytes added , 09:28, 30 July 2007

Added info on done work on 2007-07-28 and 2007-07-29.

Buddha^

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 audio streams out of them. Took influence from the AIFF-loading routine
 from ScummVM's source code.
+== 2007-07-28 (Saturday) - Decoding Apple IIGS sample header, Part 1 ==
+Modified a byte in an Apple IIGS AGI sample resource's header (At
+header offset 2) and tried the sample out by running the game
+using KEGS32 and MESS. So it turned out that that header byte
+handles playing pitch. And it's definitely exponential
+with 2**(1/12) as the base. The value seems to wrap around after 0x7F.
+== 2007-07-29 (Sunday) - Decoding Apple IIGS sample header, Part 2 ==
+Inspected how the byte in Apple IIGS AGI sample resource's header
+offset 4 affects the playing of the sample. It is the volume control,
+probably logarithmic, but not 100% sure about that yet.
+Fiddled a bit with some other header offsets and got something
+interesting and/or weird to happen but don't yet know what they
+really did :-).
+The Apple IIGS AGI sample resource's header is 54 bytes long and
+by the header comparisons I've done the following header offsets
+are the most varying ones (Some other bytes also vary, but only
+between two values in the data I've compared):
+* Header offset 2
+** The playing pitch
+* Header offset 4
+** Volume control
+* Header offsets 8 and 9
+** Sample size in bytes (Little endian 16-bit word)
+* Header offset 44
+** Unknown function, uses values x*9 for x in {0, 1, 2, 3, 4, 5, 6}
+* Header offset 45
+** Unknown function, uses values 0, 2, 6
+* Header offset 50
+** Unknown function, uses values x*9 for x in {1, 2, 3, 4, 5, 6}
+* Header offset 51
+** Unknown function, uses values 0, 1, 2, 7