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libavcodec/mjpegbdec.c

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00001 /*
00002  * Apple MJPEG-B decoder
00003  * Copyright (c) 2002 Alex Beregszaszi
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00027 #include "avcodec.h"
00028 #include "mjpeg.h"
00029 #include "mjpegdec.h"
00030 
00031 
00032 static int mjpegb_decode_frame(AVCodecContext *avctx,
00033                               void *data, int *data_size,
00034                               const uint8_t *buf, int buf_size)
00035 {
00036     MJpegDecodeContext *s = avctx->priv_data;
00037     const uint8_t *buf_end, *buf_ptr;
00038     AVFrame *picture = data;
00039     GetBitContext hgb; /* for the header */
00040     uint32_t dqt_offs, dht_offs, sof_offs, sos_offs, second_field_offs;
00041     uint32_t field_size, sod_offs;
00042 
00043     buf_ptr = buf;
00044     buf_end = buf + buf_size;
00045 
00046 read_header:
00047     /* reset on every SOI */
00048     s->restart_interval = 0;
00049     s->restart_count = 0;
00050     s->mjpb_skiptosod = 0;
00051 
00052     if (buf_end - buf_ptr >= 1 << 28)
00053         return AVERROR_INVALIDDATA;
00054 
00055     init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);
00056 
00057     skip_bits(&hgb, 32); /* reserved zeros */
00058 
00059     if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g'))
00060     {
00061         av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
00062         return 0;
00063     }
00064 
00065     field_size = get_bits_long(&hgb, 32); /* field size */
00066     av_log(avctx, AV_LOG_DEBUG, "field size: 0x%x\n", field_size);
00067     skip_bits(&hgb, 32); /* padded field size */
00068     second_field_offs = get_bits_long(&hgb, 32);
00069     av_log(avctx, AV_LOG_DEBUG, "second field offs: 0x%x\n", second_field_offs);
00070 
00071     dqt_offs = get_bits_long(&hgb, 32);
00072     av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%x\n", dqt_offs);
00073     if (dqt_offs)
00074     {
00075         init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
00076         s->start_code = DQT;
00077         ff_mjpeg_decode_dqt(s);
00078     }
00079 
00080     dht_offs = get_bits_long(&hgb, 32);
00081     av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%x\n", dht_offs);
00082     if (dht_offs)
00083     {
00084         init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
00085         s->start_code = DHT;
00086         ff_mjpeg_decode_dht(s);
00087     }
00088 
00089     sof_offs = get_bits_long(&hgb, 32);
00090     av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%x\n", sof_offs);
00091     if (sof_offs)
00092     {
00093         init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
00094         s->start_code = SOF0;
00095         if (ff_mjpeg_decode_sof(s) < 0)
00096             return -1;
00097     }
00098 
00099     sos_offs = get_bits_long(&hgb, 32);
00100     av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%x\n", sos_offs);
00101     sod_offs = get_bits_long(&hgb, 32);
00102     av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%x\n", sod_offs);
00103     if (sos_offs)
00104     {
00105         init_get_bits(&s->gb, buf_ptr + sos_offs,
00106                       8 * FFMIN(field_size, buf_end - buf_ptr - sos_offs));
00107         s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16));
00108         s->start_code = SOS;
00109         ff_mjpeg_decode_sos(s);
00110     }
00111 
00112     if (s->interlaced) {
00113         s->bottom_field ^= 1;
00114         /* if not bottom field, do not output image yet */
00115         if (s->bottom_field != s->interlace_polarity && second_field_offs)
00116         {
00117             buf_ptr = buf + second_field_offs;
00118             second_field_offs = 0;
00119             goto read_header;
00120             }
00121     }
00122 
00123     //XXX FIXME factorize, this looks very similar to the EOI code
00124 
00125     *picture= s->picture;
00126     *data_size = sizeof(AVFrame);
00127 
00128     if(!s->lossless){
00129         picture->quality= FFMAX3(s->qscale[0], s->qscale[1], s->qscale[2]);
00130         picture->qstride= 0;
00131         picture->qscale_table= s->qscale_table;
00132         memset(picture->qscale_table, picture->quality, (s->width+15)/16);
00133         if(avctx->debug & FF_DEBUG_QP)
00134             av_log(avctx, AV_LOG_DEBUG, "QP: %d\n", picture->quality);
00135         picture->quality*= FF_QP2LAMBDA;
00136     }
00137 
00138     return buf_ptr - buf;
00139 }
00140 
00141 AVCodec mjpegb_decoder = {
00142     "mjpegb",
00143     CODEC_TYPE_VIDEO,
00144     CODEC_ID_MJPEGB,
00145     sizeof(MJpegDecodeContext),
00146     ff_mjpeg_decode_init,
00147     NULL,
00148     ff_mjpeg_decode_end,
00149     mjpegb_decode_frame,
00150     CODEC_CAP_DR1,
00151     NULL,
00152     .long_name = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"),
00153 };

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