libavcodec/mjpegbdec.c

   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 libavcodec/mjpegbdec.c
  24  * Apple MJPEG-B decoder.
  25  */
  26
  27 #include "avcodec.h"
  28 #include "mjpeg.h"
  29 #include "mjpegdec.h"
  30
  31
  32 static int mjpegb_decode_frame(AVCodecContext *avctx,
  33                               void *data, int *data_size,
  34                               const uint8_t *buf, int buf_size)
  35 {
  36     MJpegDecodeContext *s = avctx->priv_data;
  37     const uint8_t *buf_end, *buf_ptr;
  38     AVFrame *picture = data;
  39     GetBitContext hgb; /* for the header */
  40     uint32_t dqt_offs, dht_offs, sof_offs, sos_offs, second_field_offs;
  41     uint32_t field_size, sod_offs;
  42
  43     buf_ptr = buf;
  44     buf_end = buf + buf_size;
  45
  46 read_header:
  47     /* reset on every SOI */
  48     s->restart_interval = 0;
  49     s->restart_count = 0;
  50     s->mjpb_skiptosod = 0;
  51
  52     init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);
  53
  54     skip_bits(&hgb, 32); /* reserved zeros */
  55
  56     if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g'))
  57     {
  58         av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
  59         return 0;
  60     }
  61
  62     field_size = get_bits_long(&hgb, 32); /* field size */
  63     av_log(avctx, AV_LOG_DEBUG, "field size: 0x%x\n", field_size);
  64     skip_bits(&hgb, 32); /* padded field size */
  65     second_field_offs = get_bits_long(&hgb, 32);
  66     av_log(avctx, AV_LOG_DEBUG, "second field offs: 0x%x\n", second_field_offs);
  67
  68     dqt_offs = get_bits_long(&hgb, 32);
  69     av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%x\n", dqt_offs);
  70     if (dqt_offs)
  71     {
  72         init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
  73         s->start_code = DQT;
  74         ff_mjpeg_decode_dqt(s);
  75     }
  76
  77     dht_offs = get_bits_long(&hgb, 32);
  78     av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%x\n", dht_offs);
  79     if (dht_offs)
  80     {
  81         init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
  82         s->start_code = DHT;
  83         ff_mjpeg_decode_dht(s);
  84     }
  85
  86     sof_offs = get_bits_long(&hgb, 32);
  87     av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%x\n", sof_offs);
  88     if (sof_offs)
  89     {
  90         init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
  91         s->start_code = SOF0;
  92         if (ff_mjpeg_decode_sof(s) < 0)
  93             return -1;
  94     }
  95
  96     sos_offs = get_bits_long(&hgb, 32);
  97     av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%x\n", sos_offs);
  98     sod_offs = get_bits_long(&hgb, 32);
  99     av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%x\n", sod_offs);
 100     if (sos_offs)
 101     {
 102 //        init_get_bits(&s->gb, buf+sos_offs, (buf_end - (buf+sos_offs))*8);
 103         init_get_bits(&s->gb, buf_ptr+sos_offs, field_size*8);
 104         s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16));
 105         s->start_code = SOS;
 106         ff_mjpeg_decode_sos(s);
 107     }
 108
 109     if (s->interlaced) {
 110         s->bottom_field ^= 1;
 111         /* if not bottom field, do not output image yet */
 112         if (s->bottom_field != s->interlace_polarity && second_field_offs)
 113         {
 114             buf_ptr = buf + second_field_offs;
 115             second_field_offs = 0;
 116             goto read_header;
 117             }
 118     }
 119
 120     //XXX FIXME factorize, this looks very similar to the EOI code
 121
 122     *picture= s->picture;
 123     *data_size = sizeof(AVFrame);
 124
 125     if(!s->lossless){
 126         picture->quality= FFMAX3(s->qscale[0], s->qscale[1], s->qscale[2]);
 127         picture->qstride= 0;
 128         picture->qscale_table= s->qscale_table;
 129         memset(picture->qscale_table, picture->quality, (s->width+15)/16);
 130         if(avctx->debug & FF_DEBUG_QP)
 131             av_log(avctx, AV_LOG_DEBUG, "QP: %d\n", picture->quality);
 132         picture->quality*= FF_QP2LAMBDA;
 133     }
 134
 135     return buf_ptr - buf;
 136 }
 137
 138 AVCodec mjpegb_decoder = {
 139     "mjpegb",
 140     CODEC_TYPE_VIDEO,
 141     CODEC_ID_MJPEGB,
 142     sizeof(MJpegDecodeContext),
 143     ff_mjpeg_decode_init,
 144     NULL,
 145     ff_mjpeg_decode_end,
 146     mjpegb_decode_frame,
 147     CODEC_CAP_DR1,
 148     NULL,
 149     .long_name = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"),
 150 };