http://pastebin.com/KjvksPDX
I think, I'm getting closer: when Flex compiler code encodes, and when Flash player decodes /negative/ 16.16 fixed point numbers, it is mistaken by one bit, so the whole part becomes doubled. On Sun, Aug 17, 2014 at 5:26 PM, Left Right <olegsivo...@gmail.com> wrote: > Sorry, the table looks crooked, here's a better view: > http://pastebin.com/rhw9sFtQ > > Best, > > Oleg > > On Sun, Aug 17, 2014 at 5:23 PM, Left Right <olegsivo...@gmail.com> wrote: >> https://git-wip-us.apache.org/repos/asf/flex-sdk/repo?p=flex-sdk.git;a=blob;f=modules/swfutils/src/java/flash/swf/SwfEncoder.java;h=03a100dda92989d537b00b96033d614c73c47801;hb=HEAD#l320 >> >> This is the code I'm talking about. >> >> What is strange about it: it doesn't do what the comment above it >> says. For example, it says that you need 2 bits to write unsigned >> integer 1 - which is obviously false: you need only one bit. In fact, >> it overestimates the number of bits needed to be written by one, >> whenever all bits are set. >> >> (You can also point fingers at the... strange technique the author >> used for assertions, but this is less important at the moment). >> >> Why am I confused about this code: even though it's wrong, the results >> I see in the player agree with the results it produce. I.e. Flash >> player, when it decodes the Matrix record, uses some procedure, which >> expects this extra bit (I'm still struggling to understand how does it >> do it, but it sure works outside the spec). >> >> I'm trying to implement a SWF linker, something that assembles SWF >> files from a different format. I used HXSWFML library for that (it's >> written in Haxe), which, in turn, uses haxe.format.swf library. The >> problem is that when I write the Matrix record using these libraries, >> I do it to the spec, but the player reads the record in some wrong >> way, which I can't understand. Somehow Flex compiler manages to >> produce results coherent with the player... Below is my dissection of >> a generated PlaceOjbect3 tag, containing a Matrix record, and its >> interpretation using haxe.format.swf and swfdump Flex utility: >> >> | id | dummy | length | >> options | >> >> |-------------+--------+----------------------------------------+----------------------------------| >> | bf | 11 | 17 00 00 00 | >> 26 00 | >> | 70 | 63 | 23 | >> hasname, hasmatrix, hascharacter | >> | 00010001 10 | 111111 | 00010111 000000000 000000000 000000000 | >> 00100110 00000000 | >> >> | depth | characterid | matrix >> | name | >> >> |-------------------+-------------------+-------------------------------+----------------------| >> | 01 00 | 02 00 | a1 c5 c6 88 17 f7 3e c4 >> 8b 98 | 73 6c 69 64 65 30 00 | >> | 1 | 2 | >> | "slide0" | >> | 00000001 00000000 | 00000010 00000000 | 10100001 11000101 >> 11000110 | | >> >> | hasscale | nscalebits | scalex | scaley | hasrotate | >> nrotatebits | rotateskew0 | >> >> |----------+------------+-----------+-----------+-----------+-------------+-------------| >> | | a1 | c5 | c6 | | >> 88 | 17 | >> | true | 8 | | | true | >> 8 | | >> | 1 | 01000 | 01 110001 | 01 110001 | 1 | >> 0 1000 | 1000 0001 | >> | | | | | | >> | | >> >> | rotateskew1 | ntranslatebits | translatex | translatey >> | padding | >> >> |-------------+----------------+-----------------+------------------+---------| >> | f7 | 3e | c4 8b 98 | >> | | >> | | 14 | 8034 (401.7) | 4467 (223.35) >> | | >> | 0111 1111 | 0111 0 | 0111110 1100010 | 0 10001011 10011 >> | 000 | >> >> The calculations I made by hand agree with haxe.format.swf, and with >> my understanding of the SWF file specification. Exactly, they give me >> this: >> >> Matrix: >> HasScale = 1 >> ScaleX = 0.44140625 >> ScaleY = 0.44140625 >> HasRotate = 1 >> RotateSkew0 = 0.50390625 >> RotateSkew1 = 0.49609375 >> TranslateX = 8034 twips = 401.7 px >> TranslateY = 4467 twips = 223.35 px >> >> Swfdump gives me: >> >> <PlaceObject2 depth='1' matrix='s1.8934174,1.8934174 >> r-4.135132,2.1351318 t8034,4467'/> >> >> If I trace the matrix from inside the player, it gives me: >> >> (a=1.8934173583984375, b=-4.1351318359375, c=2.1351318359375, >> d=1.8934173583984375, tx=401.7, ty=223.35) >> >> A result I cannot explain: the matrix was symmetrical to begin with, >> how on Earth does it arrive at different scaleX and scaleY values? >> >> Sorry for the long post. It looks to me, like this is a bug in SWF >> format implementation in Adobe Flash player, which eventually made its >> way into Flex compiler too. I would be interested to understand in >> what way exactly does it make this mistake - no matter how I tried, I >> can't generate these numbers :/ >> >> Best, >> >> Oleg
