/*
  * MPEG4 Video frame extraction

  * Copyright (c) 2003 Fabrice Bellard
  * Copyright (c) 2003 Michael Niedermayer

  *
  * 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
  */
 

 #define UNCHECKED_BITSTREAM_READER 1
 

 #include "parser.h"
 #include "mpegvideo.h"

 #include "mpeg4video.h"

 #include "mpeg4video_parser.h"

 struct Mp4vParseContext {
     ParseContext pc;
     struct MpegEncContext enc;
     int first_picture;
 };

 int ff_mpeg4_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
     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;
             }
         }
     }
 
     if(vop_found){
         /* EOF considered as end of frame */
         if (buf_size == 0)
             return 0;
         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 END_NOT_FOUND;
 }
 

 /* XXX: make it use less memory */
 static int av_mpeg4_decode_header(AVCodecParserContext *s1,
                                   AVCodecContext *avctx,
                                   const uint8_t *buf, int buf_size)
 {

     struct Mp4vParseContext *pc = s1->priv_data;
     MpegEncContext *s = &pc->enc;

     GetBitContext gb1, *gb = &gb1;
     int ret;
 
     s->avctx = avctx;
     s->current_picture_ptr = &s->current_picture;
 
     if (avctx->extradata_size && pc->first_picture){
         init_get_bits(gb, avctx->extradata, avctx->extradata_size*8);
         ret = ff_mpeg4_decode_picture_header(s, gb);
     }
 
     init_get_bits(gb, buf, 8 * buf_size);
     ret = ff_mpeg4_decode_picture_header(s, gb);

     if (s->width && (!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height)) {

         avcodec_set_dimensions(avctx, s->width, s->height);
     }

     if((s1->flags & PARSER_FLAG_USE_CODEC_TS) && s->avctx->time_base.den>0 && ret>=0){
         av_assert1(s1->pts == AV_NOPTS_VALUE);
         av_assert1(s1->dts == AV_NOPTS_VALUE);
 
         s1->pts = av_rescale_q(s->time, (AVRational){1, s->avctx->time_base.den}, (AVRational){1, 1200000});
     }
 

     s1->pict_type= s->pict_type;
     pc->first_picture = 0;
     return ret;
 }
 

 static av_cold int mpeg4video_parse_init(AVCodecParserContext *s)

 {

     struct Mp4vParseContext *pc = s->priv_data;

     ff_mpeg4videodec_static_init();
 

     pc->first_picture = 1;

     pc->enc.quant_precision=5;

     pc->enc.slice_context_count = 1;

     return 0;
 }
 
 static int mpeg4video_parse(AVCodecParserContext *s,
                            AVCodecContext *avctx,

                            const uint8_t **poutbuf, int *poutbuf_size,

                            const uint8_t *buf, int buf_size)
 {
     ParseContext *pc = s->priv_data;
     int next;
 
     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
         next= buf_size;
     }else{
         next= ff_mpeg4_find_frame_end(pc, buf, buf_size);
 

         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {

             *poutbuf = NULL;
             *poutbuf_size = 0;
             return buf_size;
         }
     }
     av_mpeg4_decode_header(s, avctx, buf, buf_size);
 

     *poutbuf = buf;

     *poutbuf_size = buf_size;
     return next;
 }
 
 

 AVCodecParser ff_mpeg4video_parser = {

     .codec_ids      = { AV_CODEC_ID_MPEG4 },

     .priv_data_size = sizeof(struct Mp4vParseContext),

     .parser_init    = mpeg4video_parse_init,
     .parser_parse   = mpeg4video_parse,

     .parser_close   = ff_parse_close,

     .split          = ff_mpeg4video_split,

 };