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FFmpeg/libavcodec/h261.c
Michael Niedermayer 9dac77a7aa argh 
Originally committed as revision 3347 to svn://svn.ffmpeg.org/ffmpeg/trunk
2004-07-26 16:49:00 +00:00

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/*
* H261 decoder
* Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
* Copyright (c) 2004 Maarten Daniels
*
* 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
*/
/**
* @file h261.c
* h261codec.
*/
#include "common.h"
#include "dsputil.h"
#include "avcodec.h"
#include "mpegvideo.h"
#include "h261data.h"
#define H261_MBA_VLC_BITS 9
#define H261_MTYPE_VLC_BITS 6
#define H261_MV_VLC_BITS 7
#define H261_CBP_VLC_BITS 9
#define TCOEFF_VLC_BITS 9
#define MAX_MBA 33
#define IS_FIL(a) ((a)&MB_TYPE_H261_FIL)
/**
* H261Context
*/
typedef struct H261Context{
MpegEncContext s;
int current_mba;
int mba_diff;
int mtype;
int current_mv_x;
int current_mv_y;
int gob_number;
int loop_filter;
int bits_left; //8 - nr of bits left of the following frame in the last byte in this frame
int last_bits; //bits left of the following frame in the last byte in this frame
}H261Context;
void ff_h261_loop_filter(H261Context * h){
MpegEncContext * const s = &h->s;
const int linesize = s->linesize;
const int uvlinesize= s->uvlinesize;
uint8_t *dest_y = s->dest[0];
uint8_t *dest_cb= s->dest[1];
uint8_t *dest_cr= s->dest[2];
s->dsp.h261_loop_filter(dest_y , linesize);
s->dsp.h261_loop_filter(dest_y + 8, linesize);
s->dsp.h261_loop_filter(dest_y + 8 * linesize , linesize);
s->dsp.h261_loop_filter(dest_y + 8 * linesize + 8, linesize);
s->dsp.h261_loop_filter(dest_cb, uvlinesize);
s->dsp.h261_loop_filter(dest_cr, uvlinesize);
}
static int h261_decode_block(H261Context *h, DCTELEM *block,
int n, int coded);
static int h261_decode_mb(H261Context *h,
DCTELEM block[6][64]);
void ff_set_qscale(MpegEncContext * s, int qscale);
/***********************************************/
/* decoding */
static VLC h261_mba_vlc;
static VLC h261_mtype_vlc;
static VLC h261_mv_vlc;
static VLC h261_cbp_vlc;
void init_vlc_rl(RLTable *rl);
static void h261_decode_init_vlc(H261Context *h){
static int done = 0;
if(!done){
done = 1;
init_vlc(&h261_mba_vlc, H261_MBA_VLC_BITS, 34,
h261_mba_bits, 1, 1,
h261_mba_code, 1, 1);
init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
h261_mtype_bits, 1, 1,
h261_mtype_code, 1, 1);
init_vlc(&h261_mv_vlc, H261_MV_VLC_BITS, 17,
&h261_mv_tab[0][1], 2, 1,
&h261_mv_tab[0][0], 2, 1);
init_vlc(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63,
&h261_cbp_tab[0][1], 2, 1,
&h261_cbp_tab[0][0], 2, 1);
init_rl(&h261_rl_tcoeff);
init_vlc_rl(&h261_rl_tcoeff);
}
}
static int h261_decode_init(AVCodecContext *avctx){
H261Context *h= avctx->priv_data;
MpegEncContext * const s = &h->s;
// set defaults
MPV_decode_defaults(s);
s->avctx = avctx;
s->width = s->avctx->width;
s->height = s->avctx->height;
s->codec_id = s->avctx->codec->id;
s->out_format = FMT_H261;
s->low_delay= 1;
avctx->pix_fmt= PIX_FMT_YUV420P;
s->codec_id= avctx->codec->id;
h261_decode_init_vlc(h);
h->bits_left = 0;
h->last_bits = 0;
return 0;
}
/**
* decodes the group of blocks header or slice header.
* @return <0 if an error occured
*/
static int h261_decode_gob_header(H261Context *h){
unsigned int val;
MpegEncContext * const s = &h->s;
/* Check for GOB Start Code */
val = show_bits(&s->gb, 15);
if(val)
return -1;
/* We have a GBSC */
skip_bits(&s->gb, 16);
h->gob_number = get_bits(&s->gb, 4); /* GN */
s->qscale = get_bits(&s->gb, 5); /* GQUANT */
/* GEI */
while (get_bits1(&s->gb) != 0) {
skip_bits(&s->gb, 8);
}
if(s->qscale==0)
return -1;
// For the first transmitted macroblock in a GOB, MBA is the absolute address. For
// subsequent macroblocks, MBA is the difference between the absolute addresses of
// the macroblock and the last transmitted macroblock.
h->current_mba = 0;
h->mba_diff = 0;
return 0;
}
/**
* decodes the group of blocks / video packet header.
* @return <0 if no resync found
*/
static int ff_h261_resync(H261Context *h){
MpegEncContext * const s = &h->s;
int left, ret;
if(show_bits(&s->gb, 15)==0){
ret= h261_decode_gob_header(h);
if(ret>=0)
return 0;
}
//ok, its not where its supposed to be ...
s->gb= s->last_resync_gb;
align_get_bits(&s->gb);
left= s->gb.size_in_bits - get_bits_count(&s->gb);
for(;left>15+1+4+5; left-=8){
if(show_bits(&s->gb, 15)==0){
GetBitContext bak= s->gb;
ret= h261_decode_gob_header(h);
if(ret>=0)
return 0;
s->gb= bak;
}
skip_bits(&s->gb, 8);
}
return -1;
}
/**
* decodes skipped macroblocks
* @return 0
*/
static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2 )
{
MpegEncContext * const s = &h->s;
int i;
s->mb_intra = 0;
for(i=mba1; i<mba2; i++){
int j, xy;
s->mb_x= ((h->gob_number-1) % 2) * 11 + i % 11;
s->mb_y= ((h->gob_number-1) / 2) * 3 + i / 11;
xy = s->mb_x + s->mb_y * s->mb_stride;
ff_init_block_index(s);
ff_update_block_index(s);
s->dsp.clear_blocks(s->block[0]);
for(j=0;j<6;j++)
s->block_last_index[j] = -1;
s->mv_dir = MV_DIR_FORWARD;
s->mv_type = MV_TYPE_16X16;
s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
s->mv[0][0][0] = 0;
s->mv[0][0][1] = 0;
s->mb_skiped = 1;
MPV_decode_mb(s, s->block);
}
return 0;
}
static int decode_mv_component(GetBitContext *gb, int v){
int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
mv_diff = mvmap[mv_diff];
if(mv_diff && !get_bits1(gb))
mv_diff= -mv_diff;
v += mv_diff;
if (v <=-16) v+= 32;
else if(v >= 16) v-= 32;
return v;
}
static int h261_decode_mb(H261Context *h,
DCTELEM block[6][64])
{
MpegEncContext * const s = &h->s;
int i, cbp, xy, old_mtype;
cbp = 63;
// Read mba
do{
h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2)+1;
}
while( h->mba_diff == MAX_MBA + 1 ); // stuffing
if ( h->mba_diff < 0 )
return -1;
h->current_mba += h->mba_diff;
if ( h->current_mba > MAX_MBA )
return -1;
s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1) % 11);
s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1) / 11);
xy = s->mb_x + s->mb_y * s->mb_stride;
ff_init_block_index(s);
ff_update_block_index(s);
s->dsp.clear_blocks(s->block[0]);
// Read mtype
old_mtype = h->mtype;
h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
h->mtype = h261_mtype_map[h->mtype];
if (IS_FIL (h->mtype))
h->loop_filter = 1;
// Read mquant
if ( IS_QUANT ( h->mtype ) ){
ff_set_qscale(s, get_bits(&s->gb, 5));
}
s->mb_intra = IS_INTRA4x4(h->mtype);
// Read mv
if ( IS_16X16 ( h->mtype ) ){
// Motion vector data is included for all MC macroblocks. MVD is obtained from the macroblock vector by subtracting the
// vector of the preceding macroblock. For this calculation the vector of the preceding macroblock is regarded as zero in the
// following three situations:
// 1) evaluating MVD for macroblocks 1, 12 and 23;
// 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
// 3) MTYPE of the previous macroblock was not MC.
if ( ( h->current_mba == 1 ) || ( h->current_mba == 12 ) || ( h->current_mba == 23 ) ||
( h->mba_diff != 1) || ( !IS_16X16 ( old_mtype ) ))
{
h->current_mv_x = 0;
h->current_mv_y = 0;
}
h->current_mv_x= decode_mv_component(&s->gb, h->current_mv_x);
h->current_mv_y= decode_mv_component(&s->gb, h->current_mv_y);
}
// Read cbp
if ( HAS_CBP( h->mtype ) ){
cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;
}
if(s->mb_intra){
s->current_picture.mb_type[xy]= MB_TYPE_INTRA;
goto intra;
}
//set motion vectors
s->mv_dir = MV_DIR_FORWARD;
s->mv_type = MV_TYPE_16X16;
s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0;
if(IS_16X16 ( h->mtype )){
s->mv[0][0][0] = h->current_mv_x * 2;//gets divided by 2 in motion compensation
s->mv[0][0][1] = h->current_mv_y * 2;
}
else{
h->current_mv_x = s->mv[0][0][0] = 0;
h->current_mv_x = s->mv[0][0][1] = 0;
}
intra:
/* decode each block */
if(s->mb_intra || HAS_CBP(h->mtype)){
for (i = 0; i < 6; i++) {
if (h261_decode_block(h, block[i], i, cbp&32) < 0){
return -1;
}
cbp+=cbp;
}
}
/* per-MB end of slice check */
{
int v= show_bits(&s->gb, 15);
if(get_bits_count(&s->gb) + 15 > s->gb.size_in_bits){
v>>= get_bits_count(&s->gb) + 15 - s->gb.size_in_bits;
}
if(v==0){
return SLICE_END;
}
}
return SLICE_OK;
}
/**
* decodes a macroblock
* @return <0 if an error occured
*/
static int h261_decode_block(H261Context * h, DCTELEM * block,
int n, int coded)
{
MpegEncContext * const s = &h->s;
int code, level, i, j, run;
RLTable *rl = &h261_rl_tcoeff;
const uint8_t *scan_table;
// For the variable length encoding there are two code tables, one being used for
// the first transmitted LEVEL in INTER, INTER+MC and INTER+MC+FIL blocks, the second
// for all other LEVELs except the first one in INTRA blocks which is fixed length
// coded with 8 bits.
// NOTE: the two code tables only differ in one VLC so we handle that manually.
scan_table = s->intra_scantable.permutated;
if (s->mb_intra){
/* DC coef */
level = get_bits(&s->gb, 8);
// 0 (00000000b) and -128 (10000000b) are FORBIDDEN
if((level&0x7F) == 0){
av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
return -1;
}
// The code 1000 0000 is not used, the reconstruction level of 1024 being coded as 1111 1111.
if (level == 255)
level = 128;
block[0] = level;
i = 1;
}else if(coded){
// Run Level Code
// EOB Not possible for first level when cbp is available (that's why the table is different)
// 0 1 1s
// * * 0*
int check = show_bits(&s->gb, 2);
i = 0;
if ( check & 0x2 ){
skip_bits(&s->gb, 2);
block[0] = ( check & 0x1 ) ? -1 : 1;
i = 1;
}
}else{
i = 0;
}
if(!coded){
s->block_last_index[n] = i - 1;
return 0;
}
for(;;){
code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
if (code < 0){
av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
return -1;
}
if (code == rl->n) {
/* escape */
// The remaining combinations of (run, level) are encoded with a 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits level.
run = get_bits(&s->gb, 6);
level = (int8_t)get_bits(&s->gb, 8);
}else if(code == 0){
break;
}else{
run = rl->table_run[code];
level = rl->table_level[code];
if (get_bits1(&s->gb))
level = -level;
}
i += run;
if (i >= 64){
av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y);
return -1;
}
j = scan_table[i];
block[j] = level;
i++;
}
s->block_last_index[n] = i-1;
return 0;
}
/**
* decodes the H261 picture header.
* @return <0 if no startcode found
*/
int h261_decode_picture_header(H261Context *h){
MpegEncContext * const s = &h->s;
int format, i;
static int h261_framecounter = 0;
uint32_t startcode;
align_get_bits(&s->gb);
startcode = (h->last_bits << (12 - (8-h->bits_left))) | get_bits(&s->gb, 20-8 - (8- h->bits_left));
for(i= s->gb.size_in_bits - get_bits_count(&s->gb); i>24; i-=1){
startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
if(startcode == 0x10)
break;
}
if (startcode != 0x10){
av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
return -1;
}
/* temporal reference */
s->picture_number = get_bits(&s->gb, 5); /* picture timestamp */
/* PTYPE starts here */
skip_bits1(&s->gb); /* split screen off */
skip_bits1(&s->gb); /* camera off */
skip_bits1(&s->gb); /* freeze picture release off */
format = get_bits1(&s->gb);
//only 2 formats possible
if (format == 0){//QCIF
s->width = 176;
s->height = 144;
s->mb_width = 11;
s->mb_height = 9;
}else{//CIF
s->width = 352;
s->height = 288;
s->mb_width = 22;
s->mb_height = 18;
}
s->mb_num = s->mb_width * s->mb_height;
skip_bits1(&s->gb); /* still image mode off */
skip_bits1(&s->gb); /* Reserved */
/* PEI */
while (get_bits1(&s->gb) != 0){
skip_bits(&s->gb, 8);
}
//h261 has no I-FRAMES, pass the test in MPV_frame_start in mpegvideo.c
if(h261_framecounter > 1)
s->pict_type = P_TYPE;
else
s->pict_type = I_TYPE;
h261_framecounter++;
h->gob_number = 0;
return 0;
}
static int h261_decode_gob(H261Context *h){
MpegEncContext * const s = &h->s;
int v;
ff_set_qscale(s, s->qscale);
/* check for empty gob */
v= show_bits(&s->gb, 15);
if(get_bits_count(&s->gb) + 15 > s->gb.size_in_bits){
v>>= get_bits_count(&s->gb) + 15 - s->gb.size_in_bits;
}
if(v==0){
h261_decode_mb_skipped(h, 0, 33);
return 0;
}
/* decode mb's */
while(h->current_mba <= MAX_MBA)
{
int ret;
/* DCT & quantize */
ret= h261_decode_mb(h, s->block);
if(ret<0){
const int xy= s->mb_x + s->mb_y*s->mb_stride;
if(ret==SLICE_END){
MPV_decode_mb(s, s->block);
if(h->loop_filter){
ff_h261_loop_filter(h);
}
h->loop_filter = 0;
h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
h261_decode_mb_skipped(h, h->current_mba, 33);
return 0;
}else if(ret==SLICE_NOEND){
av_log(s->avctx, AV_LOG_ERROR, "Slice mismatch at MB: %d\n", xy);
return -1;
}
av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", xy);
return -1;
}
MPV_decode_mb(s, s->block);
if(h->loop_filter){
ff_h261_loop_filter(h);
}
h->loop_filter = 0;
h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
}
return -1;
}
static int h261_find_frame_end(ParseContext *pc, AVCodecContext* avctx, const uint8_t *buf, int buf_size){
int vop_found, i, j, bits_left, last_bits;
uint32_t state;
H261Context *h = avctx->priv_data;
if(h){
bits_left = h->bits_left;
last_bits = h->last_bits;
}
else{
bits_left = 0;
last_bits = 0;
}
vop_found= pc->frame_start_found;
state= pc->state;
if(bits_left!=0 && !vop_found)
state = state << (8-bits_left) | last_bits;
i=0;
if(!vop_found){
for(i=0; i<buf_size; i++){
state= (state<<8) | buf[i];
for(j=0; j<8; j++){
if(( ( (state<<j) | (buf[i]>>(8-j)) )>>(32-20) == 0x10 )&&(((state >> (17-j)) & 0x4000) == 0x0)){
i++;
vop_found=1;
break;
}
}
if(vop_found)
break;
}
}
if(vop_found){
for(; i<buf_size; i++){
if(avctx->flags & CODEC_FLAG_TRUNCATED)//XXX ffplay workaround, someone a better solution?
state= (state<<8) | buf[i];
for(j=0; j<8; j++){
if(( ( (state<<j) | (buf[i]>>(8-j)) )>>(32-20) == 0x10 )&&(((state >> (17-j)) & 0x4000) == 0x0)){
pc->frame_start_found=0;
pc->state=-1;
return i-3;
}
}
}
}
pc->frame_start_found= vop_found;
pc->state= state;
return END_NOT_FOUND;
}
static int h261_parse(AVCodecParserContext *s,
AVCodecContext *avctx,
uint8_t **poutbuf, int *poutbuf_size,
const uint8_t *buf, int buf_size)
{
ParseContext *pc = s->priv_data;
int next;
next= h261_find_frame_end(pc,avctx, buf, buf_size);
if (ff_combine_frame(pc, next, (uint8_t **)&buf, &buf_size) < 0) {
*poutbuf = NULL;
*poutbuf_size = 0;
return buf_size;
}
*poutbuf = (uint8_t *)buf;
*poutbuf_size = buf_size;
return next;
}
/**
* returns the number of bytes consumed for building the current frame
*/
static int get_consumed_bytes(MpegEncContext *s, int buf_size){
int pos= (get_bits_count(&s->gb)+7)>>3;
if(s->flags&CODEC_FLAG_TRUNCATED){
pos -= s->parse_context.last_index;
if(pos<0) pos=0;// padding is not really read so this might be -1
return pos;
}else{
if(pos==0) pos=1; //avoid infinite loops (i doubt thats needed but ...)
if(pos+10>buf_size) pos=buf_size; // oops ;)
return pos;
}
}
static int h261_decode_frame(AVCodecContext *avctx,
void *data, int *data_size,
uint8_t *buf, int buf_size)
{
H261Context *h= avctx->priv_data;
MpegEncContext *s = &h->s;
int ret;
AVFrame *pict = data;
#ifdef DEBUG
printf("*****frame %d size=%d\n", avctx->frame_number, buf_size);
printf("bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
#endif
s->flags= avctx->flags;
s->flags2= avctx->flags2;
/* no supplementary picture */
if (buf_size == 0) {
return 0;
}
if(s->flags&CODEC_FLAG_TRUNCATED){
int next;
next= h261_find_frame_end(&s->parse_context,avctx, buf, buf_size);
if( ff_combine_frame(&s->parse_context, next, &buf, &buf_size) < 0 )
return buf_size;
}
retry:
init_get_bits(&s->gb, buf, buf_size*8);
if(!s->context_initialized){
if (MPV_common_init(s) < 0) //we need the idct permutaton for reading a custom matrix
return -1;
}
//we need to set current_picture_ptr before reading the header, otherwise we cant store anyting im there
if(s->current_picture_ptr==NULL || s->current_picture_ptr->data[0]){
int i= ff_find_unused_picture(s, 0);
s->current_picture_ptr= &s->picture[i];
}
ret = h261_decode_picture_header(h);
/* skip if the header was thrashed */
if (ret < 0){
av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
return -1;
}
if (s->width != avctx->width || s->height != avctx->height){
ParseContext pc= s->parse_context; //FIXME move these demuxng hack to avformat
s->parse_context.buffer=0;
MPV_common_end(s);
s->parse_context= pc;
}
if (!s->context_initialized) {
avctx->width = s->width;
avctx->height = s->height;
goto retry;
}
// for hurry_up==5
s->current_picture.pict_type= s->pict_type;
s->current_picture.key_frame= s->pict_type == I_TYPE;
/* skip everything if we are in a hurry>=5 */
if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);
if(MPV_frame_start(s, avctx) < 0)
return -1;
ff_er_frame_start(s);
/* decode each macroblock */
s->mb_x=0;
s->mb_y=0;
while(h->gob_number < (s->mb_height==18 ? 12 : 5)){
if(ff_h261_resync(h)<0)
break;
h261_decode_gob(h);
}
MPV_frame_end(s);
// h261 doesn't have byte aligned codes
// store the bits of the next frame that are left in the last byte
// in the H261Context and remember the number of stored bits
{
int bitsleft;
int current_pos= get_bits_count(&s->gb)>>3;
bitsleft = (current_pos<<3) - get_bits_count(&s->gb);
h->bits_left = - bitsleft;
if(bitsleft > 0)
h->last_bits= get_bits(&s->gb, 8 - h->bits_left);
else
h->last_bits = 0;
}
assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
assert(s->current_picture.pict_type == s->pict_type);
*pict= *(AVFrame*)&s->current_picture;
ff_print_debug_info(s, pict);
/* Return the Picture timestamp as the frame number */
/* we substract 1 because it is added on utils.c */
avctx->frame_number = s->picture_number - 1;
*data_size = sizeof(AVFrame);
return get_consumed_bytes(s, buf_size);
}
static int h261_decode_end(AVCodecContext *avctx)
{
H261Context *h= avctx->priv_data;
MpegEncContext *s = &h->s;
MPV_common_end(s);
return 0;
}
AVCodec h261_decoder = {
"h261",
CODEC_TYPE_VIDEO,
CODEC_ID_H261,
sizeof(H261Context),
h261_decode_init,
NULL,
h261_decode_end,
h261_decode_frame,
CODEC_CAP_TRUNCATED,
};
AVCodecParser h261_parser = {
{ CODEC_ID_H261 },
sizeof(ParseContext),
NULL,
h261_parse,
ff_parse_close,
};
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