* Initial implementation of the G.726 ADPCM audio codec.

Originally committed as revision 2759 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 417 insertions, 0 deletions

diff --git a/libavcodec/g726.c b/libavcodec/g726.c
new file mode 100644
index 0000000000..2166e3b5ef
--- /dev/null
+++ b/libavcodec/g726.c
@@ -0,0 +1,417 @@
+/*
+ * G.726 ADPCM audio codec 
+ * Copyright (c) 2004 Roman Shaposhnik.
+ *
+ * This is a very straightforward rendition of the G.726
+ * Section 4 "Computational Details". 
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+#include <limits.h>
+#include "avcodec.h"
+#include "common.h"
+
+/*
+ * G.726 Standard uses rather odd 11bit floating point arithmentic for 
+ * numerous occasions. It's a mistery to me why they did it this way
+ * instead of simply using 32bit integer arithmetic.
+ */
+typedef struct Float11 {
+	int sign;   /* 1bit sign */
+	int exp;    /* 4bit exponent */
+	int mant;   /* 6bit mantissa */
+} Float11;
+
+static inline Float11* i2f(int16_t i, Float11* f)
+{
+	f->sign = (i < 0);
+	if (f->sign)
+		i = -i;
+	f->exp = av_log2_16bit(i) + !!i;
+	f->mant = i? (i<<6) >> f->exp : 
+		         1<<5;
+	return f;
+}
+
+static inline int16_t mult(Float11* f1, Float11* f2)
+{
+	int res, exp;
+
+	exp = f1->exp + f2->exp;
+	res = (((f1->mant * f2->mant) + 0x30) >> 4) << 7;
+	res = exp > 26 ? res << (exp - 26) : res >> (26 - exp);
+	return (f1->sign ^ f2->sign) ? -res : res;
+}
+
+static inline int clamp(int value, int min, int max)
+{
+   if (value < min)
+       return min;
+   else if (value > max)
+       return max;
+   else 
+       return value;
+}
+
+static inline int sgn(int value)
+{
+   return (value < 0) ? -1 : 1;
+}
+
+typedef struct G726Tables {
+	int  bits;            /* bits per sample */
+	int* quant;           /* quantization table */
+	int* iquant;          /* inverse quantization table */
+	int* W;               /* special table #1 ;-) */
+	int* F;               /* special table #2 */
+} G726Tables;
+
+typedef struct G726Context {
+	 G726Tables* tbls;    /* static tables needed for computation */
+	 
+	 Float11 sr[2];       /* prev. reconstructed samples */
+	 Float11 dq[6];       /* prev. difference */
+	 int a[2];            /* second order predictor coeffs */
+	 int b[6];            /* sixth order predictor coeffs */
+	 int pk[2];           /* signs of prev. 2 sez + dq */
+	 
+	 int ap;              /* scale factor control */
+	 int yu;              /* fast scale factor */
+	 int yl;              /* slow scale factor */
+	 int dms;             /* short average magnitude of F[i] */
+	 int dml;             /* long average magnitude of F[i] */
+	 int td;              /* tone detect */
+
+	 int se;              /* estimated signal for the next iteration */
+	 int sez;             /* estimated second order prediction */
+	 int y;               /* quantizer scaling factor for the next iteration */
+} G726Context;
+
+static int quant_tbl16[] =                       /* 16kbit/s 2bits per sample */
+           { 260, INT_MAX }; 
+static int iquant_tbl16[] =
+           { 116, 365, 365, 116 };
+static int W_tbl16[] = 
+           { -22, 439, 439, -22 };
+static int F_tbl16[] =
+           { 0, 7, 7, 0 };
+	   
+static int quant_tbl24[] =                       /* 24kbit/s 3bits per sample */
+           {  7, 217, 330, INT_MAX };
+static int iquant_tbl24[] =
+           { INT_MIN, 135, 273, 373, 373, 273, 135, INT_MIN };
+static int W_tbl24[] = 
+           { -4,  30, 137, 582, 582, 137,  30, -4 }; 
+static int F_tbl24[] =
+           { 0, 1, 2, 7, 7, 2, 1, 0 };
+	   
+static int quant_tbl32[] =                       /* 32kbit/s 4bits per sample */
+           { -125,  79, 177, 245, 299, 348, 399, INT_MAX };
+static int iquant_tbl32[] =
+           { INT_MIN,   4, 135, 213, 273, 323, 373, 425,  
+	         425, 373, 323, 273, 213, 135,   4, INT_MIN };
+static int W_tbl32[] = 
+           { -12,  18,  41,  64, 112, 198, 355, 1122,
+	    1122, 355, 198, 112,  64,  41,  18, -12};
+static int F_tbl32[] = 
+           { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 };
+	   
+static int quant_tbl40[] =                      /* 40kbit/s 5bits per sample */
+           { -122, -16,  67, 138, 197, 249, 297, 338,
+	      377, 412, 444, 474, 501, 527, 552, INT_MAX };
+static int iquant_tbl40[] =
+           { INT_MIN, -66,  28, 104, 169, 224, 274, 318,  
+	         358, 395, 429, 459, 488, 514, 539, 566,
+	         566, 539, 514, 488, 459, 429, 395, 358,
+	         318, 274, 224, 169, 104,  28, -66, INT_MIN };
+static int W_tbl40[] = 
+           {   14,  14,  24,  39,  40,  41,   58,  100,
+	      141, 179, 219, 280, 358, 440,  529,  696, 
+	      696, 529, 440, 358, 280, 219,  179,  141,
+	      100,  58,  41,  40,  39,  24,   14,   14 };
+static int F_tbl40[] = 
+           { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6,
+	     6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
+
+static G726Tables G726Tables_pool[] = 
+           {{ 2, quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 },
+	    { 3, quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 },
+	    { 4, quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 },
+            { 5, quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }};
+					       
+
+/*
+ * Para 4.2.2 page 18: Adaptive quantizer. 
+ */
+static inline uint8_t quant(G726Context* c, int d)
+{
+   int sign, exp, i, dln;
+   
+   sign = i = 0;
+   if (d < 0) {
+       sign = 1;
+       d = -d;
+   }
+   exp = av_log2_16bit(d);
+   dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);
+   
+   while (c->tbls->quant[i] < INT_MAX && c->tbls->quant[i] < dln)
+        ++i;
+   
+   if (sign)
+       i = ~i;
+   if (c->tbls->bits != 2 && i == 0) /* I'm not sure this is a good idea */
+       i = 0xff;
+
+   return i; 
+}
+
+/* 
+ * Para 4.2.3 page 22: Inverse adaptive quantizer.
+ */
+static inline int16_t inverse_quant(G726Context* c, int i)
+{
+    int dql, dex, dqt;
+	
+    dql = c->tbls->iquant[i] + (c->y >> 2);
+    dex = (dql>>7) & 0xf;        /* 4bit exponent */
+    dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
+    return (dql < 0) ? 0 : ((dqt<<7) >> (14-dex)); 
+}
+
+static inline int16_t g726_iterate(G726Context* c, int16_t I)
+{
+    int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
+    Float11 f;
+    
+    dq = inverse_quant(c, I);
+    if (I >> (c->tbls->bits - 1))  /* get the sign */
+        dq = -dq;
+    re_signal = c->se + dq;
+
+    /* Transition detect */
+    ylint = (c->yl >> 15);
+    ylfrac = (c->yl >> 10) & 0x1f;
+    thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
+    if (c->td == 1 && abs(dq) > ((thr2+(thr2>>1))>>1))
+        tr = 1;
+    else
+        tr = 0;
+    
+    /* Update second order predictor coefficient A2 and A1 */
+    pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
+    dq0 = dq ? sgn(dq) : 0;
+    if (tr) {
+        c->a[0] = 0;
+	c->a[1] = 0;
+        for (i=0; i<6; i++)
+	   c->b[i] = 0;
+    } else {
+	/* This is a bit crazy, but it really is +255 not +256 */
+	fa1 = clamp((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
+	
+	c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
+	c->a[1] = clamp(c->a[1], -12288, 12288);
+        c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
+	c->a[0] = clamp(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
+
+        for (i=0; i<6; i++)
+	     c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
+    }
+
+    /* Update Dq and Sr and Pk */
+    c->pk[1] = c->pk[0];
+    c->pk[0] = pk0 ? pk0 : 1;
+    c->sr[1] = c->sr[0];
+    i2f(re_signal, &c->sr[0]);
+    for (i=5; i>0; i--)
+       c->dq[i] = c->dq[i-1];
+    i2f(dq, &c->dq[0]);
+    c->dq[0].sign = I >> (c->tbls->bits - 1); /* Isn't it crazy ?!?! */
+    
+    /* Update tone detect [I'm not sure 'tr == 0' is really needed] */
+    c->td = (tr == 0 && c->a[1] < -11776); 
+       
+    /* Update Ap */
+    c->dms += ((c->tbls->F[I]<<9) - c->dms) >> 5;
+    c->dml += ((c->tbls->F[I]<<11) - c->dml) >> 7;
+    if (tr) 
+       c->ap = 256;
+    else if (c->y > 1535 && !c->td && (abs((c->dms << 2) - c->dml) < (c->dml >> 3)))
+       c->ap += (-c->ap) >> 4;
+    else
+       c->ap += (0x200 - c->ap) >> 4; 
+
+    /* Update Yu and Yl */
+    c->yu = clamp(c->y + (((c->tbls->W[I] << 5) - c->y) >> 5), 544, 5120);
+    c->yl += c->yu + ((-c->yl)>>6);
+ 
+    /* Next iteration for Y */
+    al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
+    c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
+	
+    /* Next iteration for SE and SEZ */
+    c->se = 0;
+    for (i=0; i<6; i++)
+       c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
+    c->sez = c->se >> 1;
+    for (i=0; i<2; i++)
+       c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
+    c->se >>= 1;
+
+    return clamp(re_signal << 2, -0xffff, 0xffff);
+}
+
+static int g726_reset(G726Context* c, int bit_rate)
+{
+    int i;
+
+    c->tbls = &G726Tables_pool[bit_rate/8000 - 2];
+    for (i=0; i<2; i++) {
+       i2f(0, &c->sr[i]);
+       c->a[i] = 0;
+       c->pk[i] = 1;
+    }
+    for (i=0; i<6; i++) {
+       i2f(0, &c->dq[i]);
+       c->b[i] = 0;
+    }
+    c->ap = 0;
+    c->dms = 0;
+    c->dml = 0;
+    c->yu = 544;
+    c->yl = 34816;
+    c->td = 0;
+
+    c->se = 0;
+    c->sez = 0;
+    c->y = 544;
+
+    return 0;
+}
+
+static int16_t g726_decode(G726Context* c, int16_t i)
+{
+    return g726_iterate(c, i);
+}
+
+static int16_t g726_encode(G726Context* c, int16_t sig)
+{
+   uint8_t i;
+   
+   i = quant(c, sig/4 - c->se) & ((1<<c->tbls->bits) - 1);
+   g726_iterate(c, i);
+   return i;
+}
+
+/* Interfacing to the libavcodec */
+
+typedef struct AVG726Context {
+   G726Context c;
+   int bits_left;
+   int bit_buffer;
+   int code_size;
+} AVG726Context;
+
+static int g726_init(AVCodecContext * avctx)
+{
+    AVG726Context* c = (AVG726Context*)avctx->priv_data;
+    
+    if (avctx->sample_rate != 8000 || avctx->channels != 1 ||
+        (avctx->bit_rate != 16000 && avctx->bit_rate != 24000 &&
+	 avctx->bit_rate != 32000 && avctx->bit_rate != 40000)) {
+        av_log(avctx, AV_LOG_ERROR, "G726: unsupported audio format\n");
+	return -1;
+    }
+    g726_reset(&c->c, avctx->bit_rate);
+    c->code_size = c->c.tbls->bits;
+    c->bit_buffer = 0;
+    c->bits_left = 0;
+
+    return 0;
+}
+
+static int g726_encode_frame(AVCodecContext *avctx,
+                            uint8_t *dst, int buf_size, void *data)
+{
+    AVG726Context *c = avctx->priv_data;
+    short *samples = data;
+    PutBitContext pb;
+
+    init_put_bits(&pb, dst, 1024*1024);
+
+    for (; buf_size; buf_size--)
+       put_bits(&pb, c->code_size, g726_encode(&c->c, *samples++));
+
+    flush_put_bits(&pb);
+
+    return put_bits_count(&pb)>>3; 
+}		
+
+static int g726_decode_frame(AVCodecContext *avctx,
+                             void *data, int *data_size,
+                             uint8_t *buf, int buf_size)
+{
+    AVG726Context *c = avctx->priv_data;
+    short *samples = data;
+    uint8_t code;
+    uint8_t mask;
+    GetBitContext gb; 
+   
+    if (!buf_size)
+        goto out;
+    
+    mask = (1<<c->code_size) - 1;
+    init_get_bits(&gb, buf, buf_size * 8);
+    if (c->bits_left) {
+        int s = c->code_size - c->bits_left;;
+	code = (c->bit_buffer << s) | get_bits(&gb, s);
+	*samples++ = g726_decode(&c->c, code & mask);
+    }
+    
+    while (get_bits_count(&gb) + c->code_size <= buf_size*8)
+	*samples++ = g726_decode(&c->c, get_bits(&gb, c->code_size) & mask);
+    
+    c->bits_left = buf_size*8 - get_bits_count(&gb);
+    c->bit_buffer = get_bits(&gb, c->bits_left);
+    
+out:
+    *data_size = (uint8_t*)samples - (uint8_t*)data;
+    return buf_size;
+}
+
+#ifdef CONFIG_ENCODERS
+AVCodec adpcm_g726_encoder = {
+    "g726",
+    CODEC_TYPE_AUDIO,
+    CODEC_ID_ADPCM_G726,
+    sizeof(AVG726Context),
+    g726_init,
+    g726_encode_frame,
+    NULL,
+    NULL,
+};
+#endif //CONFIG_ENCODERS
+
+AVCodec adpcm_g726_decoder = {
+    "g726",
+    CODEC_TYPE_AUDIO,
+    CODEC_ID_ADPCM_G726,
+    sizeof(AVG726Context),
+    g726_init,
+    NULL,
+    NULL,
+    g726_decode_frame,
+};