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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 static uint32_t read_offs(AVCodecContext *avctx, GetBitContext *gb, uint32_t size, const char *err_msg){
00032     uint32_t offs= get_bits_long(gb, 32);
00033     if(offs >= size){
00034         av_log(avctx, AV_LOG_WARNING, err_msg, offs, size);
00035         return 0;
00036     }
00037     return offs;
00038 }
00039 
00040 static int mjpegb_decode_frame(AVCodecContext *avctx,
00041                               void *data, int *data_size,
00042                               AVPacket *avpkt)
00043 {
00044     const uint8_t *buf = avpkt->data;
00045     int buf_size = avpkt->size;
00046     MJpegDecodeContext *s = avctx->priv_data;
00047     const uint8_t *buf_end, *buf_ptr;
00048     AVFrame *picture = data;
00049     GetBitContext hgb; /* for the header */
00050     uint32_t dqt_offs, dht_offs, sof_offs, sos_offs, second_field_offs;
00051     uint32_t field_size, sod_offs;
00052 
00053     buf_ptr = buf;
00054     buf_end = buf + buf_size;
00055 
00056 read_header:
00057     /* reset on every SOI */
00058     s->restart_interval = 0;
00059     s->restart_count = 0;
00060     s->mjpb_skiptosod = 0;
00061 
00062     init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);
00063 
00064     skip_bits(&hgb, 32); /* reserved zeros */
00065 
00066     if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g'))
00067     {
00068         av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
00069         return 0;
00070     }
00071 
00072     field_size = get_bits_long(&hgb, 32); /* field size */
00073     av_log(avctx, AV_LOG_DEBUG, "field size: 0x%x\n", field_size);
00074     skip_bits(&hgb, 32); /* padded field size */
00075     second_field_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "second_field_offs is %d and size is %d\n");
00076     av_log(avctx, AV_LOG_DEBUG, "second field offs: 0x%x\n", second_field_offs);
00077 
00078     dqt_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dqt is %d and size is %d\n");
00079     av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%x\n", dqt_offs);
00080     if (dqt_offs)
00081     {
00082         init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
00083         s->start_code = DQT;
00084         ff_mjpeg_decode_dqt(s);
00085     }
00086 
00087     dht_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dht is %d and size is %d\n");
00088     av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%x\n", dht_offs);
00089     if (dht_offs)
00090     {
00091         init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
00092         s->start_code = DHT;
00093         ff_mjpeg_decode_dht(s);
00094     }
00095 
00096     sof_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
00097     av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%x\n", sof_offs);
00098     if (sof_offs)
00099     {
00100         init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
00101         s->start_code = SOF0;
00102         if (ff_mjpeg_decode_sof(s) < 0)
00103             return -1;
00104     }
00105 
00106     sos_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sos is %d and size is %d\n");
00107     av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%x\n", sos_offs);
00108     sod_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
00109     av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%x\n", sod_offs);
00110     if (sos_offs)
00111     {
00112 //        init_get_bits(&s->gb, buf+sos_offs, (buf_end - (buf+sos_offs))*8);
00113         init_get_bits(&s->gb, buf_ptr+sos_offs, field_size*8);
00114         s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16));
00115         s->start_code = SOS;
00116         ff_mjpeg_decode_sos(s);
00117     }
00118 
00119     if (s->interlaced) {
00120         s->bottom_field ^= 1;
00121         /* if not bottom field, do not output image yet */
00122         if (s->bottom_field != s->interlace_polarity && second_field_offs)
00123         {
00124             buf_ptr = buf + second_field_offs;
00125             second_field_offs = 0;
00126             goto read_header;
00127             }
00128     }
00129 
00130     //XXX FIXME factorize, this looks very similar to the EOI code
00131 
00132     *picture= s->picture;
00133     *data_size = sizeof(AVFrame);
00134 
00135     if(!s->lossless){
00136         picture->quality= FFMAX3(s->qscale[0], s->qscale[1], s->qscale[2]);
00137         picture->qstride= 0;
00138         picture->qscale_table= s->qscale_table;
00139         memset(picture->qscale_table, picture->quality, (s->width+15)/16);
00140         if(avctx->debug & FF_DEBUG_QP)
00141             av_log(avctx, AV_LOG_DEBUG, "QP: %d\n", picture->quality);
00142         picture->quality*= FF_QP2LAMBDA;
00143     }
00144 
00145     return buf_ptr - buf;
00146 }
00147 
00148 AVCodec mjpegb_decoder = {
00149     "mjpegb",
00150     AVMEDIA_TYPE_VIDEO,
00151     CODEC_ID_MJPEGB,
00152     sizeof(MJpegDecodeContext),
00153     ff_mjpeg_decode_init,
00154     NULL,
00155     ff_mjpeg_decode_end,
00156     mjpegb_decode_frame,
00157     CODEC_CAP_DR1,
00158     NULL,
00159     .long_name = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"),
00160 };

Generated on Fri Sep 16 2011 17:17:39 for FFmpeg by  doxygen 1.7.1