diff options
author | murf <murf@f38db490-d61c-443f-a65b-d21fe96a405b> | 2007-08-20 22:53:48 +0000 |
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committer | murf <murf@f38db490-d61c-443f-a65b-d21fe96a405b> | 2007-08-20 22:53:48 +0000 |
commit | 8b5681e22acd883fc692455b460a6385e521b683 (patch) | |
tree | ba8c79a84cc6cbddcd2d849a6b9895d6124c4452 /main/ulaw.c | |
parent | 160c516178ec81b8a2321f84b18ea8cece00f142 (diff) |
This change set fixes bug 8126 in trunk. It is implemented via compile time options, activated via the menuselect stuff, which defaults to the old way. non-zero sample data added. Translate tables expressed in microseconds instead of milliseconds, with 5-digit data now instead of 3, giving 2 more digits of precision.
git-svn-id: http://svn.digium.com/svn/asterisk/trunk@80113 f38db490-d61c-443f-a65b-d21fe96a405b
Diffstat (limited to 'main/ulaw.c')
-rw-r--r-- | main/ulaw.c | 165 |
1 files changed, 153 insertions, 12 deletions
diff --git a/main/ulaw.c b/main/ulaw.c index 2735f6cce..8e47d8a77 100644 --- a/main/ulaw.c +++ b/main/ulaw.c @@ -28,15 +28,25 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$") #include "asterisk/ulaw.h" +#include "asterisk/logger.h" +#if 0 +/* ZEROTRAP is the military recommendation to improve the encryption + * of u-Law traffic. It is irrelevant with modern encryption systems + * like AES, and will simply degrade the signal quality. + * ZEROTRAP is not implemented in AST_LIN2MU and so the coding table + * tests will fail if you use it */ #define ZEROTRAP /*!< turn on the trap as per the MIL-STD */ +#endif + #define BIAS 0x84 /*!< define the add-in bias for 16 bit samples */ #define CLIP 32635 +#ifndef G711_NEW_ALGORITHM + unsigned char __ast_lin2mu[16384]; short __ast_mulaw[256]; - static unsigned char linear2ulaw(short sample) { static int exp_lut[256] = { @@ -58,26 +68,102 @@ static unsigned char linear2ulaw(short sample) 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7 }; int sign, exponent, mantissa; unsigned char ulawbyte; - + /* Get the sample into sign-magnitude. */ sign = (sample >> 8) & 0x80; /* set aside the sign */ - if (sign != 0) + if (sign != 0) sample = -sample; /* get magnitude */ if (sample > CLIP) sample = CLIP; /* clip the magnitude */ - + /* Convert from 16 bit linear to ulaw. */ sample = sample + BIAS; exponent = exp_lut[(sample >> 7) & 0xFF]; mantissa = (sample >> (exponent + 3)) & 0x0F; ulawbyte = ~(sign | (exponent << 4) | mantissa); + #ifdef ZEROTRAP if (ulawbyte == 0) ulawbyte = 0x02; /* optional CCITT trap */ #endif + + return ulawbyte; +} + +#else + +unsigned char __ast_lin2mu[AST_ULAW_TAB_SIZE]; +short __ast_mulaw[256]; + +static unsigned char linear2ulaw(short sample, int full_coding) +{ + static const unsigned exp_lut[256] = { + 0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3, + 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4, + 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5, + 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5, + 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6, + 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6, + 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6, + 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6, + 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7 }; + unsigned sign, exponent, mantissa, mag; + unsigned char ulawbyte; + + /* Get the sample into sign-magnitude. */ + ast_ulaw_get_sign_mag(sample, &sign, &mag); + if (mag > CLIP) + mag = CLIP; /* clip the magnitude */ + + sign = (sample >> 8) & 0x80; /* set aside the sign */ + if (sign != 0) + sample = -sample; /* get magnitude */ + if (sample > CLIP) + sample = CLIP; /* clip the magnitude */ + + /* Convert from 16 bit linear to ulaw. */ + mag += BIAS; + exponent = exp_lut[(mag >> 7) & 0xFF]; + mantissa = (mag >> (exponent + 3)) & 0x0F; + + if (full_coding) { + /* full encoding, with sign and xform */ + ulawbyte = ~(sign | (exponent << 4) | mantissa); +#ifdef ZEROTRAP + if (ulawbyte == 0) + ulawbyte = 0x02; /* optional CCITT trap */ +#endif + } else { + /* half-cooked coding -- mantissa+exponent only (for lookup tab) */ + ulawbyte = (exponent << 4) | mantissa; + } return ulawbyte; } + +static inline short ulaw2linear(unsigned char ulawbyte) +{ + unsigned exponent, mantissa; + short sample; + static const short etab[]={0,132,396,924,1980,4092,8316,16764}; + + ulawbyte = ~ulawbyte; + exponent = (ulawbyte & 0x70) >> 4; + mantissa = ulawbyte & 0x0f; + sample = mantissa << (exponent + 3); + sample += etab[exponent]; + if (ulawbyte & 0x80) + sample = -sample; + return sample; +} +#endif /*! * \brief Set up mu-law conversion table @@ -85,22 +171,77 @@ static unsigned char linear2ulaw(short sample) void ast_ulaw_init(void) { int i; - for (i = 0; i < 256; i++) { - short mu, e, f, y; - static short etab[] = {0,132,396,924,1980,4092,8316,16764}; - - mu = 255 - i; - e = (mu & 0x70) / 16; + + /* + * Set up mu-law conversion table + */ +#ifndef G711_NEW_ALGORITHM + for (i = 0;i < 256;i++) { + short mu,e,f,y; + static short etab[]={0,132,396,924,1980,4092,8316,16764}; + + mu = 255-i; + e = (mu & 0x70)/16; f = mu & 0x0f; y = f * (1 << (e + 3)); y += etab[e]; - if (mu & 0x80) - y = -y; + if (mu & 0x80) y = -y; __ast_mulaw[i] = y; } /* set up the reverse (mu-law) conversion table */ for (i = -32768; i < 32768; i++) { __ast_lin2mu[((unsigned short)i) >> 2] = linear2ulaw(i); } +#else + + for (i = 0; i < 256; i++) { + __ast_mulaw[i] = ulaw2linear(i); + } + /* set up the reverse (mu-law) conversion table */ + for (i = 0; i <= 32768; i += AST_ULAW_STEP) { + AST_LIN2MU_LOOKUP(i) = linear2ulaw(i, 0 /* half-cooked */); + } +#endif + +#ifdef TEST_CODING_TABLES + for (i = -32768; i < 32768; ++i) { +#ifndef G711_NEW_ALGORITHM + unsigned char e1 = linear2ulaw(i); +#else + unsigned char e1 = linear2ulaw(i, 1); +#endif + short d1 = ulaw2linear(e1); + unsigned char e2 = AST_LIN2MU(i); + short d2 = ulaw2linear(e2); + short d3 = AST_MULAW(e1); + + if (e1 != e2 || d1 != d3 || d2 != d3) { + ast_log(LOG_WARNING, "u-Law coding tables test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d\n", + i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2); + } + } + ast_log(LOG_NOTICE, "u-Law coding table test complete.\n"); +#endif /* TEST_CODING_TABLES */ + +#ifdef TEST_TANDEM_TRANSCODING + /* tandem transcoding test */ + for (i = -32768; i < 32768; ++i) { + unsigned char e1 = AST_LIN2MU(i); + short d1 = AST_MULAW(e1); + unsigned char e2 = AST_LIN2MU(d1); + short d2 = AST_MULAW(e2); + unsigned char e3 = AST_LIN2MU(d2); + short d3 = AST_MULAW(e3); + + if (i < 0 && e1 == 0x7f && e2 == 0xff && e3 == 0xff) + continue; /* known and normal negative 0 case */ + + if (e1 != e2 || e2 != e3 || d1 != d2 || d2 != d3) { + ast_log(LOG_WARNING, "u-Law tandem transcoding test failed on %d: e1=%u, e2=%u, d1=%d, d2=%d, d3=%d\n", + i, (unsigned)e1, (unsigned)e2, (int)d1, (int)d2, (int)d3); + } + } + ast_log(LOG_NOTICE, "u-Law tandem transcoding test complete.\n"); +#endif /* TEST_TANDEM_TRANSCODING */ } |