[Ffmpeg-cvslog] r5449 - trunk/libavcodec/adpcm.c
lorenm
subversion
Sat Jun 3 06:38:11 CEST 2006
Author: lorenm
Date: Sat Jun 3 06:38:11 2006
New Revision: 5449
Modified:
trunk/libavcodec/adpcm.c
Log:
adpcm_ima & adpcm_yamaha: improved quantization
Modified: trunk/libavcodec/adpcm.c
==============================================================================
--- trunk/libavcodec/adpcm.c (original)
+++ trunk/libavcodec/adpcm.c Sat Jun 3 06:38:11 2006
@@ -203,49 +203,11 @@
static inline unsigned char adpcm_ima_compress_sample(ADPCMChannelStatus *c, short sample)
{
- int step_index;
- unsigned char nibble;
-
- int sign = 0; /* sign bit of the nibble (MSB) */
- int delta, predicted_delta;
-
- delta = sample - c->prev_sample;
-
- if (delta < 0) {
- sign = 1;
- delta = -delta;
- }
-
- step_index = c->step_index;
-
- /* nibble = 4 * delta / step_table[step_index]; */
- nibble = (delta << 2) / step_table[step_index];
-
- if (nibble > 7)
- nibble = 7;
-
- step_index += index_table[nibble];
- if (step_index < 0)
- step_index = 0;
- if (step_index > 88)
- step_index = 88;
-
- /* what the decoder will find */
- predicted_delta = ((step_table[step_index] * nibble) / 4) + (step_table[step_index] / 8);
-
- if (sign)
- c->prev_sample -= predicted_delta;
- else
- c->prev_sample += predicted_delta;
-
+ int delta = sample - c->prev_sample;
+ int nibble = FFMIN(7, abs(delta)*4/step_table[c->step_index]) + (delta<0)*8;
+ c->prev_sample = c->prev_sample + ((step_table[c->step_index] * yamaha_difflookup[nibble]) / 8);
CLAMP_TO_SHORT(c->prev_sample);
-
-
- nibble += sign << 3; /* sign * 8 */
-
- /* save back */
- c->step_index = step_index;
-
+ c->step_index = clip(c->step_index + index_table[nibble], 0, 88);
return nibble;
}
@@ -276,27 +238,23 @@
static inline unsigned char adpcm_yamaha_compress_sample(ADPCMChannelStatus *c, short sample)
{
- int i1 = 0, j1;
+ int nibble, delta;
if(!c->step) {
c->predictor = 0;
c->step = 127;
}
- j1 = sample - c->predictor;
- j1 = (j1 * 8) / c->step;
- i1 = abs(j1) / 2;
- if (i1 > 7)
- i1 = 7;
- if (j1 < 0)
- i1 += 8;
+ delta = sample - c->predictor;
+
+ nibble = FFMIN(7, abs(delta)*4/c->step) + (delta<0)*8;
- c->predictor = c->predictor + ((c->step * yamaha_difflookup[i1]) / 8);
+ c->predictor = c->predictor + ((c->step * yamaha_difflookup[nibble]) / 8);
CLAMP_TO_SHORT(c->predictor);
- c->step = (c->step * yamaha_indexscale[i1]) >> 8;
+ c->step = (c->step * yamaha_indexscale[nibble]) >> 8;
c->step = clip(c->step, 127, 24567);
- return i1;
+ return nibble;
}
static int adpcm_encode_frame(AVCodecContext *avctx,
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