133 lines
4.5 KiB
C
133 lines
4.5 KiB
C
/*
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sample.h: The conversion from internal data to output samples of differing formats.
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copyright 2007-9 by the mpg123 project - free software under the terms of the LGPL 2.1
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see COPYING and AUTHORS files in distribution or http://mpg123.org
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initially written by Thomas Orgis, taking WRITE_SAMPLE from decode.c
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Later added the end-conversion specific macros here, too.
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*/
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#ifndef SAMPLE_H
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#define SAMPLE_H
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/* mpg123lib_intern.h is included already, right? */
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/* Special case is fixed point math... which does work, but not that nice yet. */
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#ifdef REAL_IS_FIXED
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static inline short idiv_signed_rounded(long x, int shift)
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{
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x >>= (shift - 1);
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x += (x & 1);
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return (short)(x >> 1);
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}
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# define REAL_PLUS_32767 ( 32767 << 15 )
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# define REAL_MINUS_32768 ( -32768 << 15 )
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# define REAL_TO_SHORT(x) (idiv_signed_rounded(x, 15))
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/* No better code (yet). */
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# define REAL_TO_SHORT_ACCURATE(x) REAL_TO_SHORT(x)
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/* This is just here for completeness, it is not used! */
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# define REAL_TO_S32(x) (x)
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#endif
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/* From now on for single precision float... double precision is a possible option once we added some bits. But, it would be rather insane. */
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#ifndef REAL_TO_SHORT
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/* Define the accurate rounding function. */
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# if (defined REAL_IS_FLOAT) && (defined IEEE_FLOAT)
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/* This function is only available for IEEE754 single-precision values
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This is nearly identical to proper rounding, just -+0.5 is rounded to 0 */
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static inline short ftoi16(float x)
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{
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union
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{
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float f;
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int32_t i;
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} u_fi;
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u_fi.f = x + 12582912.0f; /* Magic Number: 2^23 + 2^22 */
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return (short)u_fi.i;
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}
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# define REAL_TO_SHORT_ACCURATE(x) ftoi16(x)
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# else
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/* The "proper" rounding, plain C, a bit slow. */
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# define REAL_TO_SHORT_ACCURATE(x) (short)((x)>0.0?(x)+0.5:(x)-0.5)
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# endif
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/* Now define the normal rounding. */
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# ifdef ACCURATE_ROUNDING
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# define REAL_TO_SHORT(x) REAL_TO_SHORT_ACCURATE(x)
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# else
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/* Non-accurate rounding... simple truncation. Fastest, most LSB errors. */
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# define REAL_TO_SHORT(x) (short)(x)
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# endif
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#endif /* REAL_TO_SHORT */
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/* We should add dithering for S32, too? */
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#ifndef REAL_TO_S32
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# ifdef ACCURATE_ROUNDING
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# define REAL_TO_S32(x) (int32_t)((x)>0.0?(x)+0.5:(x)-0.5)
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# else
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# define REAL_TO_S32(x) (int32_t)(x)
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# endif
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#endif
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#ifndef REAL_PLUS_32767
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# define REAL_PLUS_32767 32767.0
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#endif
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#ifndef REAL_MINUS_32768
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# define REAL_MINUS_32768 -32768.0
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#endif
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#ifndef REAL_PLUS_S32
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# define REAL_PLUS_S32 2147483647.0
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#endif
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#ifndef REAL_MINUS_S32
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# define REAL_MINUS_S32 -2147483648.0
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#endif
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/* The actual storage of a decoded sample is separated in the following macros.
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We can handle different types, we could also handle dithering here. */
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/* Macro to produce a short (signed 16bit) output sample from internal representation,
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which may be float, double or indeed some integer for fixed point handling. */
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#define WRITE_SHORT_SAMPLE(samples,sum,clip) \
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if( (sum) > REAL_PLUS_32767) { *(samples) = 0x7fff; (clip)++; } \
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else if( (sum) < REAL_MINUS_32768) { *(samples) = -0x8000; (clip)++; } \
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else { *(samples) = REAL_TO_SHORT(sum); }
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/* Same as above, but always using accurate rounding. Would we want softer clipping here, too? */
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#define WRITE_SHORT_SAMPLE_ACCURATE(samples,sum,clip) \
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if( (sum) > REAL_PLUS_32767) { *(samples) = 0x7fff; (clip)++; } \
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else if( (sum) < REAL_MINUS_32768) { *(samples) = -0x8000; (clip)++; } \
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else { *(samples) = REAL_TO_SHORT_ACCURATE(sum); }
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/*
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32bit signed
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We do clipping with the same old borders... but different conversion.
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We see here that we need extra work for non-16bit output... we optimized for 16bit.
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-0x7fffffff-1 is the minimum 32 bit signed integer value expressed so that MSVC
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does not give a compile time warning.
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*/
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#define WRITE_S32_SAMPLE(samples,sum,clip) \
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{ \
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real tmpsum = REAL_MUL((sum),S32_RESCALE); \
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if( tmpsum > REAL_PLUS_S32 ){ *(samples) = 0x7fffffff; (clip)++; } \
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else if( tmpsum < REAL_MINUS_S32 ) { *(samples) = -0x7fffffff-1; (clip)++; } \
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else { *(samples) = REAL_TO_S32(tmpsum); } \
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}
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/* Produce an 8bit sample, via 16bit intermediate. */
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#define WRITE_8BIT_SAMPLE(samples,sum,clip) \
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{ \
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short write_8bit_tmp; \
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if( (sum) > REAL_PLUS_32767) { write_8bit_tmp = 0x7fff; (clip)++; } \
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else if( (sum) < REAL_MINUS_32768) { write_8bit_tmp = -0x8000; (clip)++; } \
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else { write_8bit_tmp = REAL_TO_SHORT(sum); } \
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*(samples) = fr->conv16to8[write_8bit_tmp>>AUSHIFT]; \
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}
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#ifndef REAL_IS_FIXED
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#define WRITE_REAL_SAMPLE(samples,sum,clip) *(samples) = ((real)1./SHORT_SCALE)*(sum)
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#endif
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#endif
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