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Code Issues Releases Activity

replace custom bitstream reader with get_bits/vlc()

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Originally committed as revision 4085 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2005-03-26 23:51:13 +00:00
parent fcbc799cd3
commit 083b80b53a
1 changed files with 27 additions and 52 deletions
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79
libavcodec/wnv1.c
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@ -25,6 +25,7 @@
#include "avcodec.h"
#include "common.h"
#include "bitstream.h"
typedef struct WNV1Context{
@ -32,59 +33,27 @@ typedef struct WNV1Context{
AVFrame pic;
int shift;
/* bit buffer */
unsigned long bitbuf;
int bits;
uint8_t *buf;
GetBitContext gb;
} WNV1Context;
static uint16_t code_tab[16][2]={
{0x1FD,9}, {0xFD,8}, {0x7D,7}, {0x3D,6}, {0x1D,5}, {0x0D,4}, {0x005,3},
{0x000,1},
{0x004,3}, {0x0C,4}, {0x1C,5}, {0x3C,6}, {0x7C,7}, {0xFC,8}, {0x1FC,9}, {0xFF,8}
};
#define CODE_VLC_BITS 9
static VLC code_vlc;
/* returns modified base_value */
static inline int wnv1_get_code(WNV1Context *w, int base_value)
{
int v = 0;
if (w->bits < 16) { /* need to fill bit buffer */
w->bitbuf |= LE_16(w->buf) << w->bits;
w->buf += 2;
w->bits += 16;
}
int v = get_vlc2(&w->gb, code_vlc.table, CODE_VLC_BITS, 1);
/* escape code */
if ((w->bitbuf & 0xFF) == 0xFF) {
w->bitbuf >>= 8;
w->bits -= 8;
if (w->bits < 16) { /* need to fill bit buffer */
w->bitbuf |= LE_16(w->buf) << w->bits;
w->buf += 2;
w->bits += 16;
}
v = w->bitbuf & (0xFF >> w->shift);
w->bitbuf >>= 8 - w->shift;
w->bits -= 8 - w->shift;
return v << w->shift;
}
/* zero code */
if (!(w->bitbuf & 1)) {
w->bitbuf >>= 1;
w->bits--;
return base_value;
}
/* reversed unary code and sign */
while (w->bits && w->bitbuf & 1) {
w->bitbuf >>= 1;
w->bits--;
v++;
}
w->bitbuf >>= 1;
w->bits--;
if(w->bitbuf & 1)
v = -v;
w->bitbuf >>= 1;
w->bits--;
v <<= w->shift;
return base_value + v;
if(v==15)
return ff_reverse[ get_bits(&w->gb, 8 - w->shift) ];
else
return base_value + ((v - 7)<<w->shift);
}
static int decode_frame(AVCodecContext *avctx,
@ -106,11 +75,11 @@ static int decode_frame(AVCodecContext *avctx,
return -1;
}
p->key_frame = 1;
l->bitbuf = 0;
l->bits = 0;
l->buf = buf + 8;
for(i=8; i<buf_size; i++)
buf[i]= ff_reverse[ buf[i] ]; //FIXME ensure that the buffer is modifyable or use a temp one
init_get_bits(&l->gb, buf+8, (buf_size-8)*8);
if (buf[2] >> 4 == 6)
l->shift = 2;
else {
@ -153,6 +122,12 @@ static int decode_init(AVCodecContext *avctx){
l->avctx = avctx;
avctx->pix_fmt = PIX_FMT_YUV422P;
if(!code_vlc.table){
init_vlc(&code_vlc, CODE_VLC_BITS, 16,
&code_tab[0][1], 4, 2,
&code_tab[0][0], 4, 2, 1);
}
return 0;
}