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Diffstat (limited to 'codecs/mp3/include/itype.h')
| -rwxr-xr-x | codecs/mp3/include/itype.h | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/codecs/mp3/include/itype.h b/codecs/mp3/include/itype.h new file mode 100755 index 000000000..0b24f40e1 --- /dev/null +++ b/codecs/mp3/include/itype.h @@ -0,0 +1,108 @@ +/*____________________________________________________________________________ + + FreeAmp - The Free MP3 Player + + MP3 Decoder originally Copyright (C) 1995-1997 Xing Technology + Corp. http://www.xingtech.com + + Portions Copyright (C) 1998 EMusic.com + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + + $Id$ +____________________________________________________________________________*/ + +/*--------------------------------------------------------------- + +mpeg Layer II audio decoder, integer version +variable type control + +-----------------------------------------------------------------*/ +/*----------------------------------------------------------------- +Variable types can have a large impact on performance. If the +native type int is 32 bit or better, setting all variables to the +native int is probably the best bet. Machines with fast floating +point handware will probably run faster with the floating point +version of this decoder. + +On 16 bit machines, use the native 16 bit int where possible +with special consideration given to the multiplies used in +the dct and window (see below). + + +The code uses the type INT32 when 32 or more bits are required. +Use the native int if possible. +Signed types are required for all but DCTCOEF which may be unsigned. + +THe major parts of the decoder are: bit stream unpack (iup.c), +dct (cidct.c), and window (iwinq.c). The compute time relationship +is usually unpack < dct < window. + +-------------------------------------------------------------------*/ + +/*-------------- dct cidct.c ------------------------------------------- +dct input is type SAMPLEINT, output is WININT + +DCTCOEF: dct coefs, 16 or more bits required +DCTBITS: fractional bits in dct coefs. Coefs are unsigned in + the range 0.50 to 10.2. DCTBITS=10 is a compromise + between precision and the possibility of overflowing + intermediate results. + + +DCTSATURATE: If set, saturates dct output to 16 bit. + Dct output may overflow if WININT is 16 bit, overflow + is rare, but very noisy. Define to 1 for 16 bit WININT. + Define to 0 otherwise. + +The multiply used in the dct (routine forward_bf in cidct.c) requires +the multiplication of a 32 bit variable by a 16 bit unsigned coef +to produce a signed 32 bit result. On 16 bit machines this could be +faster than a full 32x32 multiply. + +------------------------------------------------------------------*/ +/*-------------- WINDOW iwinq.c --------------------------------------- +window input is type WININT, output is short (16 bit pcm audio) + +window coefs WINBITS fractional bits, + coefs are signed range in -1.15 to 0.96. + WINBITS=14 is maximum for 16 bit signed representation. + Some CPU's will multiply faster with fewer bits. + WINBITS less that 8 may cause noticeable quality loss. + +WINMULT defines the multiply used in the window (iwinq.c) +WINMULT must produce a 32 bit (or better) result, although both +multipliers may be 16 bit. A 16x16-->32 multiply may offer +a performance advantage if the compiler can be coerced into +doing the right thing. +------------------------------------------------------------------*/ +/*-- settings for MS C++ 4.0 flat 32 bit (long=int=32bit) --*/ +/*-- asm replacement modules must use these settings ---*/ + +typedef long INT32; +typedef unsigned long UINT32; + +typedef int SAMPLEINT; + +typedef int DCTCOEF; + +#define DCTBITS 10 +#define DCTSATURATE 0 + +typedef int WININT; +typedef int WINCOEF; + +#define WINBITS 10 +#define WINMULT(x,coef) ((x)*(coef)) |