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FFmpeg/libavcodec/h261dec.c

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/*
* H261 decoder
* Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
* Copyright (c) 2004 Maarten Daniels
*
* This file is part of FFmpeg.
*
* FFmpeg 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 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file h261dec.c
* H.261 decoder.
*/
#include "dsputil.h"
#include "avcodec.h"
#include "mpegvideo.h"
#include "h261.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 MBA_STUFFING 33
#define MBA_STARTCODE 34
extern uint8_t ff_h261_rl_table_store[2][2*MAX_RUN + MAX_LEVEL + 3];
static VLC h261_mba_vlc;
static VLC h261_mtype_vlc;
static VLC h261_mv_vlc;
static VLC h261_cbp_vlc;
static int h261_decode_block(H261Context * h, DCTELEM * block, int n, int coded);
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, 35,
h261_mba_bits, 1, 1,
h261_mba_code, 1, 1, 1);
init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
h261_mtype_bits, 1, 1,
h261_mtype_code, 1, 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, 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, 1);
init_rl(&h261_rl_tcoeff, ff_h261_rl_table_store);
init_vlc_rl(&h261_rl_tcoeff, 1);
}
}
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->coded_width;
s->height = s->avctx->coded_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->gob_start_code_skipped = 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;
if ( !h->gob_start_code_skipped ){
/* 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_start_code_skipped = 0;
h->gob_number = get_bits(&s->gb, 4); /* GN */
s->qscale = get_bits(&s->gb, 5); /* GQUANT */
/* Check if gob_number is valid */
if (s->mb_height==18){ //cif
if ((h->gob_number<=0) || (h->gob_number>12))
return -1;
}
else{ //qcif
if ((h->gob_number!=1) && (h->gob_number!=3) && (h->gob_number!=5))
return -1;
}
/* 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 ( h->gob_start_code_skipped ){
ret= h261_decode_gob_header(h);
if(ret>=0)
return 0;
}
else{
if(show_bits(&s->gb, 15)==0){
ret= h261_decode_gob_header(h);
if(ret>=0)
return 0;
}
//OK, it is not where it is 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);
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_skipped = 1;
h->mtype &= ~MB_TYPE_H261_FIL;
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);
/* check if mv_diff is valid */
if ( mv_diff < 0 )
return v;
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){
MpegEncContext * const s = &h->s;
int i, cbp, xy;
cbp = 63;
// Read mba
do{
h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2);
/* Check for slice end */
/* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
if (h->mba_diff == MBA_STARTCODE){ // start code
h->gob_start_code_skipped = 1;
return SLICE_END;
}
}
while( h->mba_diff == MBA_STUFFING ); // stuffing
if ( h->mba_diff < 0 ){
if ( get_bits_count(&s->gb) + 7 >= s->gb.size_in_bits )
return SLICE_END;
av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
return SLICE_ERROR;
}
h->mba_diff += 1;
h->current_mba += h->mba_diff;
if ( h->current_mba > MBA_STUFFING )
return SLICE_ERROR;
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);
// Read mtype
h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
h->mtype = h261_mtype_map[h->mtype];
// 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))
{
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);
}else{
h->current_mv_x = 0;
h->current_mv_y = 0;
}
// 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;
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;
intra:
/* decode each block */
if(s->mb_intra || HAS_CBP(h->mtype)){
s->dsp.clear_blocks(s->block[0]);
for (i = 0; i < 6; i++) {
if (h261_decode_block(h, s->block[i], i, cbp&32) < 0){
return SLICE_ERROR;
}
cbp+=cbp;
}
}else{
for (i = 0; i < 6; i++)
s->block_last_index[i]= -1;
}
MPV_decode_mb(s, s->block);
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 = get_sbits(&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
*/
static int h261_decode_picture_header(H261Context *h){
MpegEncContext * const s = &h->s;
int format, i;
uint32_t startcode= 0;
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 */
i= get_bits(&s->gb, 5); /* picture timestamp */
if(i < (s->picture_number&31))
i += 32;
s->picture_number = (s->picture_number&~31) + i;
s->avctx->time_base= (AVRational){1001, 30000};
s->current_picture.pts= s->picture_number;
/* 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, but if we pass FF_I_TYPE for the first frame, the codec crashes if it does
// not contain all I-blocks (e.g. when a packet is lost)
s->pict_type = FF_P_TYPE;
h->gob_number = 0;
return 0;
}
static int h261_decode_gob(H261Context *h){
MpegEncContext * const s = &h->s;
ff_set_qscale(s, s->qscale);
/* decode mb's */
while(h->current_mba <= MBA_STUFFING)
{
int ret;
/* DCT & quantize */
ret= h261_decode_mb(h);
if(ret<0){
if(ret==SLICE_END){
h261_decode_mb_skipped(h, h->current_mba, 33);
return 0;
}
av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y*s->mb_stride);
return -1;
}
h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
}
return -1;
}
/**
* 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)>>3;
if(pos==0) pos=1; //avoid infinite loops (i doubt that is 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,
const uint8_t *buf, int buf_size)
{
H261Context *h= avctx->priv_data;
MpegEncContext *s = &h->s;
int ret;
AVFrame *pict = data;
#ifdef DEBUG
av_log(avctx, AV_LOG_DEBUG, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
av_log(avctx, AV_LOG_DEBUG, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
#endif
s->flags= avctx->flags;
s->flags2= avctx->flags2;
h->gob_start_code_skipped=0;
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 cannot 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->coded_width || s->height != avctx->coded_height){
ParseContext pc= s->parse_context; //FIXME move this demuxing hack to libavformat
s->parse_context.buffer=0;
MPV_common_end(s);
s->parse_context= pc;
}
if (!s->context_initialized) {
avcodec_set_dimensions(avctx, s->width, s->height);
goto retry;
}
// for hurry_up==5
s->current_picture.pict_type= s->pict_type;
s->current_picture.key_frame= s->pict_type == FF_I_TYPE;
/* skip everything if we are in a hurry>=5 */
if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);
if( (avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type==FF_B_TYPE)
||(avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type!=FF_I_TYPE)
|| avctx->skip_frame >= AVDISCARD_ALL)
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);
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_ptr;
ff_print_debug_info(s, pict);
*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_DR1,
};