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mp3 audio decoding didn't work on big-endian architectures

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git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@1319 b3059339-0415-0410-9bf9-f77b7e298cf2
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jkeil 2001-07-14 16:52:09 +00:00
parent b91e9d9bff
commit ecbc8847c4
1 changed files with 43 additions and 1 deletions
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44
mp3lib/decod386.c
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@ -11,17 +11,59 @@
*/
#include "../config.h"
#if 0
/* old WRITE_SAMPLE */
/* is portable */
#define WRITE_SAMPLE(samples,sum,clip) { \
if( (sum) > 32767.0) { *(samples) = 0x7fff; (clip)++; } \
else if( (sum) < -32768.0) { *(samples) = -0x8000; (clip)++; }\
else { *(samples) = sum; } \
}
#else
/* new WRITE_SAMPLE */
/*
* should be the same as the "old WRITE_SAMPLE" macro above, but uses
* some tricks to avoid double->int conversions and floating point compares.
*
* Here's how it works:
* ((((65536.0 * 65536.0 * 16)+(65536.0 * 0.5))* 65536.0)) is
* 0x0010000080000000LL in hex. It computes 0x0010000080000000LL + sum
* as a double IEEE fp value and extracts the low-order 32-bits from the
* IEEE fp representation stored in memory. The 2^56 bit in the constant
* is intended to force the bits of "sum" into the least significant bits
* of the double mantissa. After an integer substraction of 0x80000000
* we have the original double value "sum" converted to an 32-bit int value.
*
* (Is that really faster than the clean and simple old version of the macro?)
*/
/*
* On a SPARC cpu, we fetch the low-order 32-bit from the second 32-bit
* word of the double fp value stored in memory. On an x86 cpu, we fetch it
* from the first 32-bit word.
* I'm not sure if the WORDS_BIGENDIAN feature test covers all possible memory
* layouts of double floating point values an all cpu architectures. If
* it doesn't work for you, just enable the "old WRITE_SAMPLE" macro.
*/
#if WORDS_BIGENDIAN
#define MANTISSA_OFFSET 1
#else
#define MANTISSA_OFFSET 0
#endif
/* sizeof(int) == 4 */
#define WRITE_SAMPLE(samples,sum,clip) { \
double dtemp; long v; \
dtemp = ((((65536.0 * 65536.0 * 16)+(65536.0 * 0.5))* 65536.0)) + (sum);\
v = ((*(int *)&dtemp) - 0x80000000); \
v = (((int *)&dtemp)[MANTISSA_OFFSET] - 0x80000000); \
if( v > 32767) { *(samples) = 0x7fff; (clip)++; } \
else if( v < -32768) { *(samples) = -0x8000; (clip)++; } \
else { *(samples) = v; } \
}
#endif
/*