h263dec.c

Trolltech公司发布的图形界面操作系统。可在qt-embedded-2.3.7平台上编译为嵌入式图形界面操作系统。

/*
 * H263 decoder
 * Copyright (c) 2001 Fabrice Bellard.
 *
 * 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
 */
#include "avcodec.h"
#include "dsputil.h"
#include "mpegvideo.h"

#if 1
#define PRINT_QP(a, b) {}
#else
#define PRINT_QP(a, b) printf(a, b)
#endif

//#define DEBUG
//#define PRINT_FRAME_TIME
#ifdef PRINT_FRAME_TIME
static inline long long rdtsc()
{
	long long l;
	asm volatile(	"rdtsc\n\t"
		: "=A" (l)
	);
//	printf("%d\n", int(l/1000));
	return l;
}
#endif

static int h263_decode_init(AVCodecContext *avctx)
{
    MpegEncContext *s = avctx->priv_data;

    s->avctx = avctx;
    s->out_format = FMT_H263;

    s->width = avctx->width;
    s->height = avctx->height;
    s->workaround_bugs= avctx->workaround_bugs;

    // set defaults
    s->quant_precision=5;
    s->progressive_sequence=1;
    s->decode_mb= ff_h263_decode_mb;

    /* select sub codec */
    switch(avctx->codec->id) {
    case CODEC_ID_H263:
        s->gob_number = 0;
        break;
    case CODEC_ID_MPEG4:
        s->time_increment_bits = 4; /* default value for broken headers */
        s->h263_pred = 1;
        s->has_b_frames = 1; //default, might be overriden in the vol header during header parsing
        break;
    case CODEC_ID_MSMPEG4V1:
        s->h263_msmpeg4 = 1;
        s->h263_pred = 1;
        s->msmpeg4_version=1;
        break;
    case CODEC_ID_MSMPEG4V2:
        s->h263_msmpeg4 = 1;
        s->h263_pred = 1;
        s->msmpeg4_version=2;
        break;
    case CODEC_ID_MSMPEG4V3:
        s->h263_msmpeg4 = 1;
        s->h263_pred = 1;
        s->msmpeg4_version=3;
        break;
    case CODEC_ID_WMV1:
        s->h263_msmpeg4 = 1;
        s->h263_pred = 1;
        s->msmpeg4_version=4;
        break;
    case CODEC_ID_WMV2:
        s->h263_msmpeg4 = 1;
        s->h263_pred = 1;
        s->msmpeg4_version=5;
        break;
    case CODEC_ID_H263I:
        s->h263_intel = 1;
        break;
    default:
        return -1;
    }
    s->codec_id= avctx->codec->id;

    /* for h263, we allocate the images after having read the header */
    if (avctx->codec->id != CODEC_ID_H263 && avctx->codec->id != CODEC_ID_MPEG4)
        if (MPV_common_init(s) < 0)
            return -1;

    if (s->h263_msmpeg4)
        ff_msmpeg4_decode_init(s);
    else
        h263_decode_init_vlc(s);
    
    return 0;
}

static int h263_decode_end(AVCodecContext *avctx)
{
    MpegEncContext *s = avctx->priv_data;

    MPV_common_end(s);
    return 0;
}

/**
 * retunrs 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->divx_version>=500){
        //we would have to scan through the whole buf to handle the weird reordering ...
        return buf_size; 
    }else 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 decode_slice(MpegEncContext *s){
    s->last_resync_gb= s->gb;
    s->first_slice_line= 1;
        
    s->resync_mb_x= s->mb_x;
    s->resync_mb_y= s->mb_y;

    s->y_dc_scale= s->y_dc_scale_table[ s->qscale ];
    s->c_dc_scale= s->c_dc_scale_table[ s->qscale ];
    
    if(s->partitioned_frame){
        const int qscale= s->qscale;

        if(s->codec_id==CODEC_ID_MPEG4){
            if(ff_mpeg4_decode_partitions(s) < 0)
                return -1; 
        }
        
        /* restore variables which where modified */
        s->first_slice_line=1;
        s->mb_x= s->resync_mb_x;
        s->mb_y= s->resync_mb_y;
        s->qscale= qscale;
        s->y_dc_scale= s->y_dc_scale_table[ s->qscale ];
        s->c_dc_scale= s->c_dc_scale_table[ s->qscale ];
    }

    for(; s->mb_y < s->mb_height; s->mb_y++) {
        /* per-row end of slice checks */
        if(s->msmpeg4_version){
            if(s->resync_mb_y + s->slice_height == s->mb_y){
                const int xy= s->mb_x + s->mb_y*s->mb_width;
                s->error_status_table[xy-1]|= AC_END|DC_END|MV_END;
                return 0;
            }
        }
        
        if(s->msmpeg4_version==1){
            s->last_dc[0]=
            s->last_dc[1]=
            s->last_dc[2]= 128;
        }
    
        ff_init_block_index(s);
        for(; s->mb_x < s->mb_width; s->mb_x++) {
            int ret;

            ff_update_block_index(s);

            if(s->resync_mb_x == s->mb_x && s->resync_mb_y+1 == s->mb_y){
                s->first_slice_line=0; 
            }

            /* DCT & quantize */
	    s->dsp.clear_blocks(s->block[0]);
            
            s->mv_dir = MV_DIR_FORWARD;
            s->mv_type = MV_TYPE_16X16;
//printf("%d %d %06X\n", ret, get_bits_count(&s->gb), show_bits(&s->gb, 24));
            ret= s->decode_mb(s, s->block);
            
            PRINT_QP("%2d", s->qscale);
            MPV_decode_mb(s, s->block);

            if(ret<0){
                const int xy= s->mb_x + s->mb_y*s->mb_width;
                if(ret==SLICE_END){
//printf("%d %d %d %06X\n", s->mb_x, s->mb_y, s->gb.size*8 - get_bits_count(&s->gb), show_bits(&s->gb, 24));
                    s->error_status_table[xy]|= AC_END;
                    if(!s->partitioned_frame)
                        s->error_status_table[xy]|= MV_END|DC_END;

                    s->padding_bug_score--;
                        
                    if(++s->mb_x >= s->mb_width){
                        s->mb_x=0;
                        ff_draw_horiz_band(s);
                        s->mb_y++;
                    }
                    return 0; 
                }else if(ret==SLICE_NOEND){
                    fprintf(stderr,"Slice mismatch at MB: %d\n", xy);
                    return -1;
                }
                fprintf(stderr,"Error at MB: %d\n", xy);
                s->error_status_table[xy]|= AC_ERROR;
                if(!s->partitioned_frame)
                    s->error_status_table[xy]|= DC_ERROR|MV_ERROR;
    
                return -1;
            }
        }
        
        ff_draw_horiz_band(s);
        
        PRINT_QP("%s", "\n");
        
        s->mb_x= 0;
    }
    
    assert(s->mb_x==0 && s->mb_y==s->mb_height);

    /* try to detect the padding bug */
    if(      s->codec_id==CODEC_ID_MPEG4
       &&   (s->workaround_bugs&FF_BUG_AUTODETECT) 
       &&    s->gb.size*8 - get_bits_count(&s->gb) >=0
       &&    s->gb.size*8 - get_bits_count(&s->gb) < 48
       &&   !s->resync_marker
       &&   !s->data_partitioning){
        
        const int bits_count= get_bits_count(&s->gb);
        const int bits_left = s->gb.size*8 - bits_count;
        
        if(bits_left==0 || bits_left>8){
            s->padding_bug_score++;
        } else if(bits_left != 1){
            int v= show_bits(&s->gb, 8);
            v|= 0x7F >> (7-(bits_count&7));

            if(v==0x7F)
                s->padding_bug_score--;
            else
                s->padding_bug_score++;            
        }
        
        if(s->padding_bug_score > -2)
            s->workaround_bugs |=  FF_BUG_NO_PADDING;
        else
            s->workaround_bugs &= ~FF_BUG_NO_PADDING;
    }

    // handle formats which dont have unique end markers
    if(s->msmpeg4_version || (s->workaround_bugs&FF_BUG_NO_PADDING)){ //FIXME perhaps solve this more cleanly
        int left= s->gb.size*8 - get_bits_count(&s->gb);
        int max_extra=7;
        
        /* no markers in M$ crap */
        if(s->msmpeg4_version && s->pict_type==I_TYPE)
            max_extra+= 17;
        
        /* buggy padding but the frame should still end approximately at the bitstream end */
        if((s->workaround_bugs&FF_BUG_NO_PADDING) && s->error_resilience>=3)
            max_extra+= 48;
        else if((s->workaround_bugs&FF_BUG_NO_PADDING))
            max_extra+= 256*256*256*64;
        
        if(left>max_extra){
            fprintf(stderr, "discarding %d junk bits at end, next would be %X\n", left, show_bits(&s->gb, 24));
        }
        else if(left<0){
            fprintf(stderr, "overreading %d bits\n", -left);
        }else
            s->error_status_table[s->mb_num-1]|= AC_END|MV_END|DC_END;
        
        return 0;
    }

    fprintf(stderr, "slice end not reached but screenspace end (%d left %06X)\n", 
            s->gb.size*8 - get_bits_count(&s->gb),
            show_bits(&s->gb, 24));
    return -1;
}

/**
 * finds the end of the current frame in the bitstream.
 * @return the position of the first byte of the next frame, or -1
 */
static int mpeg4_find_frame_end(MpegEncContext *s, UINT8 *buf, int buf_size){
    ParseContext *pc= &s->parse_context;
    int vop_found, i;
    uint32_t state;
    
    vop_found= pc->frame_start_found;
    state= pc->state;
    
    i=0;
    if(!vop_found){
        for(i=0; i<buf_size; i++){
            state= (state<<8) | buf[i];
            if(state == 0x1B6){
                i++;
                vop_found=1;
                break;
            }
        }
    }
    
    for(; i<buf_size; i++){
        state= (state<<8) | buf[i];
        if((state&0xFFFFFF00) == 0x100){
            pc->frame_start_found=0;
            pc->state=-1; 
            return i-3;
        }
    }
    pc->frame_start_found= vop_found;
    pc->state= state;
    return -1;
}

static int h263_decode_frame(AVCodecContext *avctx, 
                             void *data, int *data_size,
                             UINT8 *buf, int buf_size)
{
    MpegEncContext *s = avctx->priv_data;
    int ret,i;
    AVPicture *pict = data; 
    float new_aspect;
    
#ifdef PRINT_FRAME_TIME
uint64_t time= rdtsc();
#endif
#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->hurry_up= avctx->hurry_up;
    s->error_resilience= avctx->error_resilience;

    s->flags= avctx->flags;

    *data_size = 0;
   
   /* no supplementary picture */
    if (buf_size == 0) {
        return 0;
    }
    
    if(s->flags&CODEC_FLAG_TRUNCATED){
        int next;
        ParseContext *pc= &s->parse_context;
        
        pc->last_index= pc->index;

        if(s->codec_id==CODEC_ID_MPEG4){
            next= mpeg4_find_frame_end(s, buf, buf_size);
        }else{
            fprintf(stderr, "this codec doesnt support truncated bitstreams\n");
            return -1;
        }
        if(next==-1){
            if(buf_size + FF_INPUT_BUFFER_PADDING_SIZE + pc->index > pc->buffer_size){
                pc->buffer_size= buf_size + pc->index + 10*1024;
                pc->buffer= realloc(pc->buffer, pc->buffer_size);
            }

            memcpy(&pc->buffer[pc->index], buf, buf_size);
            pc->index += buf_size;
            return buf_size;
        }

        if(pc->index){
            if(next + FF_INPUT_BUFFER_PADDING_SIZE + pc->index > pc->buffer_size){
                pc->buffer_size= next + pc->index + 10*1024;
                pc->buffer= realloc(pc->buffer, pc->buffer_size);
            }