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Diffstat (limited to 'src/libmpg123/sample.h')
| -rw-r--r-- | src/libmpg123/sample.h | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/src/libmpg123/sample.h b/src/libmpg123/sample.h new file mode 100644 index 0000000..2515078 --- /dev/null +++ b/src/libmpg123/sample.h @@ -0,0 +1,118 @@ +/* + sample.h: The conversion from internal data to output samples of differing formats. + + copyright 2007-9 by the mpg123 project - free software under the terms of the LGPL 2.1 + see COPYING and AUTHORS files in distribution or http://mpg123.org + initially written by Thomas Orgis, taking WRITE_SAMPLE from decode.c + Later added the end-conversion specific macros here, too. +*/ + +#ifndef SAMPLE_H +#define SAMPLE_H + +/* mpg123lib_intern.h is included already, right? */ + +/* Special case is fixed point math... which does work, but not that nice yet. */ +#ifdef REAL_IS_FIXED +static inline short idiv_signed_rounded(long x, int shift) +{ + x >>= (shift - 1); + x += (x & 1); + return (short)(x >> 1); +} +# define REAL_PLUS_32767 ( 32767 << 15 ) +# define REAL_MINUS_32768 ( -32768 << 15 ) +# define REAL_TO_SHORT(x) (idiv_signed_rounded(x, 15)) +/* This is just here for completeness, it is not used! */ +# define REAL_TO_S32(x) (x) +#endif + +/* From now on for single precision float... double precision is a possible option once we added some bits. But, it would be rather insane. */ +#ifndef REAL_TO_SHORT +# ifdef ACCURATE_ROUNDING +/* Optimized accurate rounding onlu for IEEE float + This is nearly identical to proper rounding, just -+0.5 is rounded to 0 */ +# if (defined REAL_IS_FLOAT) && (defined IEEE_FLOAT) +/* this function is only available for IEEE754 single-precision values */ +static inline short ftoi16(float x) +{ + union + { + float f; + int32_t i; + } u_fi; + u_fi.f = x + 12582912.0f; /* Magic Number: 2^23 + 2^22 */ + return (short)u_fi.i; +} +# define REAL_TO_SHORT(x) ftoi16(x) +# else +/* The "proper" rounding, plain C, a bit slow. */ +# define REAL_TO_SHORT(x) (short)((x)>0.0?(x)+0.5:(x)-0.5) +# endif +# else +/* Non-accurate rounding... simple truncation. Fastest, most LSB errors. */ +# define REAL_TO_SHORT(x) (short)(x) +# endif +#endif + +#ifndef REAL_TO_S32 +# ifdef ACCURATE_ROUNDING +# define REAL_TO_S32(x) (int32_t)((x)>0.0?(x)+0.5:(x)-0.5) +# else +# define REAL_TO_S32(x) (int32_t)(x) +# endif +#endif + +#ifndef REAL_PLUS_32767 +# define REAL_PLUS_32767 32767.0 +#endif +#ifndef REAL_MINUS_32768 +# define REAL_MINUS_32768 -32768.0 +#endif +#ifndef REAL_PLUS_S32 +# define REAL_PLUS_S32 2147483647.0 +#endif +#ifndef REAL_MINUS_S32 +# define REAL_MINUS_S32 -2147483648.0 +#endif + + +/* The actual storage of a decoded sample is separated in the following macros. + We can handle different types, we could also handle dithering here. */ + +/* Macro to produce a short (signed 16bit) output sample from internal representation, + which may be float, double or indeed some integer for fixed point handling. */ +#define WRITE_SHORT_SAMPLE(samples,sum,clip) \ + if( (sum) > REAL_PLUS_32767) { *(samples) = 0x7fff; (clip)++; } \ + else if( (sum) < REAL_MINUS_32768) { *(samples) = -0x8000; (clip)++; } \ + else { *(samples) = REAL_TO_SHORT(sum); } + +/* + 32bit signed + We do clipping with the same old borders... but different conversion. + We see here that we need extra work for non-16bit output... we optimized for 16bit. + -0x7fffffff-1 is the minimum 32 bit signed integer value expressed so that MSVC + does not give a compile time warning. +*/ +#define WRITE_S32_SAMPLE(samples,sum,clip) \ + { \ + real tmpsum = REAL_MUL((sum),S32_RESCALE); \ + if( tmpsum > REAL_PLUS_S32 ){ *(samples) = 0x7fffffff; (clip)++; } \ + else if( tmpsum < REAL_MINUS_S32 ) { *(samples) = -0x7fffffff-1; (clip)++; } \ + else { *(samples) = REAL_TO_S32(tmpsum); } \ + } + +/* Produce an 8bit sample, via 16bit intermediate. */ +#define WRITE_8BIT_SAMPLE(samples,sum,clip) \ +{ \ + short write_8bit_tmp; \ + if( (sum) > REAL_PLUS_32767) { write_8bit_tmp = 0x7fff; (clip)++; } \ + else if( (sum) < REAL_MINUS_32768) { write_8bit_tmp = -0x8000; (clip)++; } \ + else { write_8bit_tmp = REAL_TO_SHORT(sum); } \ + *(samples) = fr->conv16to8[write_8bit_tmp>>AUSHIFT]; \ +} +#ifndef REAL_IS_FIXED +#define WRITE_REAL_SAMPLE(samples,sum,clip) *(samples) = ((real)1./SHORT_SCALE)*(sum) +#endif + +#endif |