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Allow hardcoding of ulaw and alaw tables.

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Originally committed as revision 22762 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Reimar Döffinger
2010-04-01 17:54:15 +00:00
parent 8eaa6e0e04
commit fa034b4427
4 changed files with 168 additions and 76 deletions
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79
libavcodec/pcm.c
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@@ -27,92 +27,19 @@
#include "avcodec.h"
#include "libavutil/common.h" /* for av_reverse */
#include "bytestream.h"
#include "pcm_tablegen.h"
#define MAX_CHANNELS 64
/* from g711.c by SUN microsystems (unrestricted use) */
#define SIGN_BIT (0x80) /* Sign bit for a A-law byte. */
#define QUANT_MASK (0xf) /* Quantization field mask. */
#define NSEGS (8) /* Number of A-law segments. */
#define SEG_SHIFT (4) /* Left shift for segment number. */
#define SEG_MASK (0x70) /* Segment field mask. */
#define BIAS (0x84) /* Bias for linear code. */
/*
* alaw2linear() - Convert an A-law value to 16-bit linear PCM
*
*/
static av_cold int alaw2linear(unsigned char a_val)
{
int t;
int seg;
a_val ^= 0x55;
t = a_val & QUANT_MASK;
seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
if(seg) t= (t + t + 1 + 32) << (seg + 2);
else t= (t + t + 1 ) << 3;
return (a_val & SIGN_BIT) ? t : -t;
}
static av_cold int ulaw2linear(unsigned char u_val)
{
int t;
/* Complement to obtain normal u-law value. */
u_val = ~u_val;
/*
* Extract and bias the quantization bits. Then
* shift up by the segment number and subtract out the bias.
*/
t = ((u_val & QUANT_MASK) << 3) + BIAS;
t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
return (u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS);
}
/* 16384 entries per table */
static uint8_t linear_to_alaw[16384];
static uint8_t linear_to_ulaw[16384];
static av_cold void build_xlaw_table(uint8_t *linear_to_xlaw,
int (*xlaw2linear)(unsigned char),
int mask)
{
int i, j, v, v1, v2;
j = 0;
for(i=0;i<128;i++) {
if (i != 127) {
v1 = xlaw2linear(i ^ mask);
v2 = xlaw2linear((i + 1) ^ mask);
v = (v1 + v2 + 4) >> 3;
} else {
v = 8192;
}
for(;j<v;j++) {
linear_to_xlaw[8192 + j] = (i ^ mask);
if (j > 0)
linear_to_xlaw[8192 - j] = (i ^ (mask ^ 0x80));
}
}
linear_to_xlaw[0] = linear_to_xlaw[1];
}
static av_cold int pcm_encode_init(AVCodecContext *avctx)
{
avctx->frame_size = 1;
switch(avctx->codec->id) {
case CODEC_ID_PCM_ALAW:
build_xlaw_table(linear_to_alaw, alaw2linear, 0xd5);
pcm_alaw_tableinit();
break;
case CODEC_ID_PCM_MULAW:
build_xlaw_table(linear_to_ulaw, ulaw2linear, 0xff);
pcm_ulaw_tableinit();
break;
default:
break;