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                               AVPacket *avpkt)
  35 {
  36     const uint8_t *buf = avpkt->data;
  37     int buf_size = avpkt->size;
  38     MJpegDecodeContext *s = avctx->priv_data;
  39     const uint8_t *buf_end, *buf_ptr;
  40     AVFrame *picture = data;
  41     GetBitContext hgb; /* for the header */
  42     uint32_t dqt_offs, dht_offs, sof_offs, sos_offs, second_field_offs;
  43     uint32_t field_size, sod_offs;
  44
  45     buf_ptr = buf;
  46     buf_end = buf + buf_size;
  47
  48 read_header:
  49     /* reset on every SOI */
  50     s->restart_interval = 0;
  51     s->restart_count = 0;
  52     s->mjpb_skiptosod = 0;
  53
  54     init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);
  55
  56     skip_bits(&hgb, 32); /* reserved zeros */
  57
  58     if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g'))
  59     {
  60         av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
  61         return 0;
  62     }
  63
  64     field_size = get_bits_long(&hgb, 32); /* field size */
  65     av_log(avctx, AV_LOG_DEBUG, "field size: 0x%x\n", field_size);
  66     skip_bits(&hgb, 32); /* padded field size */
  67     second_field_offs = get_bits_long(&hgb, 32);
  68     av_log(avctx, AV_LOG_DEBUG, "second field offs: 0x%x\n", second_field_offs);
  69
  70     dqt_offs = get_bits_long(&hgb, 32);
  71     av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%x\n", dqt_offs);
  72     if (dqt_offs)
  73     {
  74         init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
  75         s->start_code = DQT;
  76         ff_mjpeg_decode_dqt(s);
  77     }
  78
  79     dht_offs = get_bits_long(&hgb, 32);
  80     av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%x\n", dht_offs);
  81     if (dht_offs)
  82     {
  83         init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
  84         s->start_code = DHT;
  85         ff_mjpeg_decode_dht(s);
  86     }
  87
  88     sof_offs = get_bits_long(&hgb, 32);
  89     av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%x\n", sof_offs);
  90     if (sof_offs)
  91     {
  92         init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
  93         s->start_code = SOF0;
  94         if (ff_mjpeg_decode_sof(s) < 0)
  95             return -1;
  96     }
  97
  98     sos_offs = get_bits_long(&hgb, 32);
  99     av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%x\n", sos_offs);
 100     sod_offs = get_bits_long(&hgb, 32);
 101     av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%x\n", sod_offs);
 102     if (sos_offs)
 103     {
 104 //        init_get_bits(&s->gb, buf+sos_offs, (buf_end - (buf+sos_offs))*8);
 105         init_get_bits(&s->gb, buf_ptr+sos_offs, field_size*8);
 106         s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16));
 107         s->start_code = SOS;
 108         ff_mjpeg_decode_sos(s);
 109     }
 110
 111     if (s->interlaced) {
 112         s->bottom_field ^= 1;
 113         /* if not bottom field, do not output image yet */
 114         if (s->bottom_field != s->interlace_polarity && second_field_offs)
 115         {
 116             buf_ptr = buf + second_field_offs;
 117             second_field_offs = 0;
 118             goto read_header;
 119             }
 120     }
 121
 122     //XXX FIXME factorize, this looks very similar to the EOI code
 123
 124     *picture= s->picture;
 125     *data_size = sizeof(AVFrame);
 126
 127     if(!s->lossless){
 128         picture->quality= FFMAX3(s->qscale[0], s->qscale[1], s->qscale[2]);
 129         picture->qstride= 0;
 130         picture->qscale_table= s->qscale_table;
 131         memset(picture->qscale_table, picture->quality, (s->width+15)/16);
 132         if(avctx->debug & FF_DEBUG_QP)
 133             av_log(avctx, AV_LOG_DEBUG, "QP: %d\n", picture->quality);
 134         picture->quality*= FF_QP2LAMBDA;
 135     }
 136
 137     return buf_ptr - buf;
 138 }
 139
 140 AVCodec mjpegb_decoder = {
 141     "mjpegb",
 142     CODEC_TYPE_VIDEO,
 143     CODEC_ID_MJPEGB,
 144     sizeof(MJpegDecodeContext),
 145     ff_mjpeg_decode_init,
 146     NULL,
 147     ff_mjpeg_decode_end,
 148     mjpegb_decode_frame,
 149     CODEC_CAP_DR1,
 150     NULL,
 151     .long_name = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"),
 152 };