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  1. /*
  2.  * Apple MJPEG-B decoder
  3.  * Copyright (c) 2002 Alex Beregszaszi
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. /**
  23.  * @file
  24.  * Apple MJPEG-B decoder.
  25.  */
  26.  
  27. #include "avcodec.h"
  28. #include "mjpeg.h"
  29. #include "mjpegdec.h"
  30.  
  31. static uint32_t read_offs(AVCodecContext *avctx, GetBitContext *gb, uint32_t size, const char *err_msg){
  32.     uint32_t offs= get_bits_long(gb, 32);
  33.     if(offs >= size){
  34.         av_log(avctx, AV_LOG_WARNING, err_msg, offs, size);
  35.         return 0;
  36.     }
  37.     return offs;
  38. }
  39.  
  40. static int mjpegb_decode_frame(AVCodecContext *avctx,
  41.                               void *data, int *got_frame,
  42.                               AVPacket *avpkt)
  43. {
  44.     const uint8_t *buf = avpkt->data;
  45.     int buf_size = avpkt->size;
  46.     MJpegDecodeContext *s = avctx->priv_data;
  47.     const uint8_t *buf_end, *buf_ptr;
  48.     GetBitContext hgb; /* for the header */
  49.     uint32_t dqt_offs, dht_offs, sof_offs, sos_offs, second_field_offs;
  50.     uint32_t field_size, sod_offs;
  51.     int ret;
  52.  
  53.     buf_ptr = buf;
  54.     buf_end = buf + buf_size;
  55.     s->got_picture = 0;
  56.  
  57. read_header:
  58.     /* reset on every SOI */
  59.     s->restart_interval = 0;
  60.     s->restart_count = 0;
  61.     s->mjpb_skiptosod = 0;
  62.  
  63.     if (buf_end - buf_ptr >= 1 << 28)
  64.         return AVERROR_INVALIDDATA;
  65.  
  66.     init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);
  67.  
  68.     skip_bits(&hgb, 32); /* reserved zeros */
  69.  
  70.     if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g'))
  71.     {
  72.         av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
  73.         return AVERROR_INVALIDDATA;
  74.     }
  75.  
  76.     field_size = get_bits_long(&hgb, 32); /* field size */
  77.     av_log(avctx, AV_LOG_DEBUG, "field size: 0x%x\n", field_size);
  78.     skip_bits(&hgb, 32); /* padded field size */
  79.     second_field_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "second_field_offs is %d and size is %d\n");
  80.     av_log(avctx, AV_LOG_DEBUG, "second field offs: 0x%x\n", second_field_offs);
  81.  
  82.     dqt_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dqt is %d and size is %d\n");
  83.     av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%x\n", dqt_offs);
  84.     if (dqt_offs)
  85.     {
  86.         init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
  87.         s->start_code = DQT;
  88.         if (ff_mjpeg_decode_dqt(s) < 0 &&
  89.             (avctx->err_recognition & AV_EF_EXPLODE))
  90.           return AVERROR_INVALIDDATA;
  91.     }
  92.  
  93.     dht_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dht is %d and size is %d\n");
  94.     av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%x\n", dht_offs);
  95.     if (dht_offs)
  96.     {
  97.         init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
  98.         s->start_code = DHT;
  99.         ff_mjpeg_decode_dht(s);
  100.     }
  101.  
  102.     sof_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
  103.     av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%x\n", sof_offs);
  104.     if (sof_offs)
  105.     {
  106.         init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
  107.         s->start_code = SOF0;
  108.         if (ff_mjpeg_decode_sof(s) < 0)
  109.             return -1;
  110.     }
  111.  
  112.     sos_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sos is %d and size is %d\n");
  113.     av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%x\n", sos_offs);
  114.     sod_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
  115.     av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%x\n", sod_offs);
  116.     if (sos_offs)
  117.     {
  118.         init_get_bits(&s->gb, buf_ptr + sos_offs,
  119.                       8 * FFMIN(field_size, buf_end - buf_ptr - sos_offs));
  120.         s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16));
  121.         s->start_code = SOS;
  122.         if (ff_mjpeg_decode_sos(s, NULL, NULL) < 0 &&
  123.             (avctx->err_recognition & AV_EF_EXPLODE))
  124.           return AVERROR_INVALIDDATA;
  125.     }
  126.  
  127.     if (s->interlaced) {
  128.         s->bottom_field ^= 1;
  129.         /* if not bottom field, do not output image yet */
  130.         if (s->bottom_field != s->interlace_polarity && second_field_offs)
  131.         {
  132.             buf_ptr = buf + second_field_offs;
  133.             goto read_header;
  134.             }
  135.     }
  136.  
  137.     //XXX FIXME factorize, this looks very similar to the EOI code
  138.  
  139.     if(!s->got_picture) {
  140.         av_log(avctx, AV_LOG_WARNING, "no picture\n");
  141.         return buf_size;
  142.     }
  143.  
  144.     if ((ret = av_frame_ref(data, s->picture_ptr)) < 0)
  145.         return ret;
  146.     *got_frame = 1;
  147.  
  148.     if (!s->lossless && avctx->debug & FF_DEBUG_QP) {
  149.         av_log(avctx, AV_LOG_DEBUG, "QP: %d\n",
  150.                FFMAX3(s->qscale[0], s->qscale[1], s->qscale[2]));
  151.     }
  152.  
  153.     return buf_size;
  154. }
  155.  
  156. AVCodec ff_mjpegb_decoder = {
  157.     .name           = "mjpegb",
  158.     .long_name      = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"),
  159.     .type           = AVMEDIA_TYPE_VIDEO,
  160.     .id             = AV_CODEC_ID_MJPEGB,
  161.     .priv_data_size = sizeof(MJpegDecodeContext),
  162.     .init           = ff_mjpeg_decode_init,
  163.     .close          = ff_mjpeg_decode_end,
  164.     .decode         = mjpegb_decode_frame,
  165.     .capabilities   = CODEC_CAP_DR1,
  166.     .max_lowres     = 3,
  167. };
  168.