Libav 0.7.1
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00001 /* 00002 * Apple MJPEG-B decoder 00003 * Copyright (c) 2002 Alex Beregszaszi 00004 * 00005 * This file is part of Libav. 00006 * 00007 * Libav 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 * Libav 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 Libav; 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, NULL, NULL); 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_ptr; 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 ff_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 .max_lowres = 3, 00160 .long_name = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"), 00161 };