2 * Apple MJPEG-B decoder
3 * Copyright (c) 2002 Alex Beregszaszi
5 * This file is part of FFmpeg.
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.
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.
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
23 * @file libavcodec/mjpegbdec.c
24 * Apple MJPEG-B decoder.
32 static int mjpegb_decode_frame(AVCodecContext *avctx,
33 void *data, int *data_size,
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;
46 buf_end = buf + buf_size;
49 /* reset on every SOI */
50 s->restart_interval = 0;
52 s->mjpb_skiptosod = 0;
54 init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);
56 skip_bits(&hgb, 32); /* reserved zeros */
58 if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g'))
60 av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
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);
70 dqt_offs = get_bits_long(&hgb, 32);
71 av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%x\n", dqt_offs);
74 init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
76 ff_mjpeg_decode_dqt(s);
79 dht_offs = get_bits_long(&hgb, 32);
80 av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%x\n", dht_offs);
83 init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
85 ff_mjpeg_decode_dht(s);
88 sof_offs = get_bits_long(&hgb, 32);
89 av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%x\n", sof_offs);
92 init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
94 if (ff_mjpeg_decode_sof(s) < 0)
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);
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));
108 ff_mjpeg_decode_sos(s);
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)
116 buf_ptr = buf + second_field_offs;
117 second_field_offs = 0;
122 //XXX FIXME factorize, this looks very similar to the EOI code
124 *picture= s->picture;
125 *data_size = sizeof(AVFrame);
128 picture->quality= FFMAX3(s->qscale[0], s->qscale[1], s->qscale[2]);
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;
137 return buf_ptr - buf;
140 AVCodec mjpegb_decoder = {
144 sizeof(MJpegDecodeContext),
145 ff_mjpeg_decode_init,
151 .long_name = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"),