text: /*
   * Apple MJPEG-B decoder
   * Copyright (c) 2002 Alex Beregszaszi
   *
   * 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
   * Apple MJPEG-B decoder.
   */
  
  #include <inttypes.h>
  
  #include "avcodec.h"
  #include "mjpeg.h"
  #include "mjpegdec.h"
  
  static uint32_t read_offs(AVCodecContext *avctx, GetBitContext *gb, uint32_t size, const char *err_msg){
      uint32_t offs= get_bits_long(gb, 32);
      if(offs >= size){
          av_log(avctx, AV_LOG_WARNING, err_msg, offs, size);
          return 0;
      }
      return offs;
  }
  
  static int mjpegb_decode_frame(AVCodecContext *avctx,
                                void *data, int *got_frame,
                                AVPacket *avpkt)
  {
      const uint8_t *buf = avpkt->data;
      int buf_size = avpkt->size;
      MJpegDecodeContext *s = avctx->priv_data;
      const uint8_t *buf_end, *buf_ptr;
      GetBitContext hgb; /* for the header */
      uint32_t dqt_offs, dht_offs, sof_offs, sos_offs, second_field_offs;
      uint32_t field_size, sod_offs;
      int ret;
  
      buf_ptr = buf;
      buf_end = buf + buf_size;
      s->got_picture = 0;
  
  read_header:
      /* reset on every SOI */
      s->restart_interval = 0;
      s->restart_count = 0;
      s->mjpb_skiptosod = 0;
  
      if (buf_end - buf_ptr >= 1 << 28)
          return AVERROR_INVALIDDATA;
  
      init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);
  
      skip_bits(&hgb, 32); /* reserved zeros */
  
      if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g'))
      {
          av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
          return AVERROR_INVALIDDATA;
      }
  
      field_size = get_bits_long(&hgb, 32); /* field size */
      av_log(avctx, AV_LOG_DEBUG, "field size: 0x%"PRIx32"\n", field_size);
      skip_bits(&hgb, 32); /* padded field size */
      second_field_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "second_field_offs is %d and size is %d\n");
      av_log(avctx, AV_LOG_DEBUG, "second field offs: 0x%"PRIx32"\n",
             second_field_offs);
  
      dqt_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dqt is %d and size is %d\n");
      av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%"PRIx32"\n", dqt_offs);
      if (dqt_offs)
      {
          init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
          s->start_code = DQT;
          if (ff_mjpeg_decode_dqt(s) < 0 &&
              (avctx->err_recognition & AV_EF_EXPLODE))
            return AVERROR_INVALIDDATA;
      }
  
      dht_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dht is %d and size is %d\n");
      av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%"PRIx32"\n", dht_offs);
      if (dht_offs)
      {
          init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
          s->start_code = DHT;
          ff_mjpeg_decode_dht(s);
      }
  
      sof_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
      av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%"PRIx32"\n", sof_offs);
      if (sof_offs)
      {
          init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
          s->start_code = SOF0;
          if (ff_mjpeg_decode_sof(s) < 0)
              return -1;
      }
  
      sos_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sos is %d and size is %d\n");
      av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%"PRIx32"\n", sos_offs);
      sod_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
      av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%"PRIx32"\n", sod_offs);
      if (sos_offs)
      {
          init_get_bits(&s->gb, buf_ptr + sos_offs,
                        8 * FFMIN(field_size, buf_end - buf_ptr - sos_offs));
          s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16));
          s->start_code = SOS;
          if (ff_mjpeg_decode_sos(s, NULL, 0, NULL) < 0 &&
              (avctx->err_recognition & AV_EF_EXPLODE))
            return AVERROR_INVALIDDATA;
      }
  
      if (s->interlaced) {
          s->bottom_field ^= 1;
          /* if not bottom field, do not output image yet */
          if (s->bottom_field != s->interlace_polarity && second_field_offs)
          {
              buf_ptr = buf + second_field_offs;
              goto read_header;
              }
      }
  
      //XXX FIXME factorize, this looks very similar to the EOI code
  
      if(!s->got_picture) {
          av_log(avctx, AV_LOG_WARNING, "no picture\n");
          return buf_size;
      }
  
      if ((ret = av_frame_ref(data, s->picture_ptr)) < 0)
          return ret;
      *got_frame = 1;
  
      if (!s->lossless && avctx->debug & FF_DEBUG_QP) {
          av_log(avctx, AV_LOG_DEBUG, "QP: %d\n",
                 FFMAX3(s->qscale[0], s->qscale[1], s->qscale[2]));
      }
  
      return buf_size;
  }
  
  AVCodec ff_mjpegb_decoder = {
  	.name           = "mjpegb",
      .long_name      = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"),
      .type           = AVMEDIA_TYPE_VIDEO,
      .id             = AV_CODEC_ID_MJPEGB,
      .priv_data_size = sizeof(MJpegDecodeContext),
      .init           = ff_mjpeg_decode_init,
      .close          = ff_mjpeg_decode_end,
      .decode         = mjpegb_decode_frame,
      .capabilities   = CODEC_CAP_DR1,
      .max_lowres     = 3,
  };
  