1/* 2 * Kega Game Video (KGV1) decoder 3 * Copyright (c) 2010 Daniel Verkamp 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 24 * Kega Game Video decoder 25 */ 26 27#include "libavutil/intreadwrite.h" 28#include "avcodec.h" 29 30typedef struct { 31 AVCodecContext *avctx; 32 AVFrame pic; 33 uint16_t *prev, *cur; 34} KgvContext; 35 36static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt) 37{ 38 const uint8_t *buf = avpkt->data; 39 const uint8_t *buf_end = buf + avpkt->size; 40 KgvContext * const c = avctx->priv_data; 41 int offsets[7]; 42 uint16_t *out, *prev; 43 int outcnt = 0, maxcnt; 44 int w, h, i; 45 46 if (avpkt->size < 2) 47 return -1; 48 49 w = (buf[0] + 1) * 8; 50 h = (buf[1] + 1) * 8; 51 buf += 2; 52 53 if (avcodec_check_dimensions(avctx, w, h)) 54 return -1; 55 56 if (w != avctx->width || h != avctx->height) 57 avcodec_set_dimensions(avctx, w, h); 58 59 maxcnt = w * h; 60 61 out = av_realloc(c->cur, w * h * 2); 62 if (!out) 63 return -1; 64 c->cur = out; 65 66 prev = av_realloc(c->prev, w * h * 2); 67 if (!prev) 68 return -1; 69 c->prev = prev; 70 71 for (i = 0; i < 7; i++) 72 offsets[i] = -1; 73 74 while (outcnt < maxcnt && buf_end - 2 > buf) { 75 int code = AV_RL16(buf); 76 buf += 2; 77 78 if (!(code & 0x8000)) { 79 out[outcnt++] = code; // rgb555 pixel coded directly 80 } else { 81 int count; 82 uint16_t *inp; 83 84 if ((code & 0x6000) == 0x6000) { 85 // copy from previous frame 86 int oidx = (code >> 10) & 7; 87 int start; 88 89 count = (code & 0x3FF) + 3; 90 91 if (offsets[oidx] < 0) { 92 if (buf_end - 3 < buf) 93 break; 94 offsets[oidx] = AV_RL24(buf); 95 buf += 3; 96 } 97 98 start = (outcnt + offsets[oidx]) % maxcnt; 99 100 if (maxcnt - start < count) 101 break; 102 103 inp = prev + start; 104 } else { 105 // copy from earlier in this frame 106 int offset = (code & 0x1FFF) + 1; 107 108 if (!(code & 0x6000)) { 109 count = 2; 110 } else if ((code & 0x6000) == 0x2000) { 111 count = 3; 112 } else { 113 if (buf_end - 1 < buf) 114 break; 115 count = 4 + *buf++; 116 } 117 118 if (outcnt < offset) 119 break; 120 121 inp = out + outcnt - offset; 122 } 123 124 if (maxcnt - outcnt < count) 125 break; 126 127 for (i = 0; i < count; i++) 128 out[outcnt++] = inp[i]; 129 } 130 } 131 132 if (outcnt - maxcnt) 133 av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt); 134 135 c->pic.data[0] = (uint8_t *)c->cur; 136 c->pic.linesize[0] = w * 2; 137 138 *data_size = sizeof(AVFrame); 139 *(AVFrame*)data = c->pic; 140 141 FFSWAP(uint16_t *, c->cur, c->prev); 142 143 return avpkt->size; 144} 145 146static av_cold int decode_init(AVCodecContext *avctx) 147{ 148 KgvContext * const c = avctx->priv_data; 149 150 c->avctx = avctx; 151 avctx->pix_fmt = PIX_FMT_RGB555; 152 153 return 0; 154} 155 156static av_cold int decode_end(AVCodecContext *avctx) 157{ 158 KgvContext * const c = avctx->priv_data; 159 160 av_freep(&c->cur); 161 av_freep(&c->prev); 162 163 return 0; 164} 165 166AVCodec kgv1_decoder = { 167 "kgv1", 168 AVMEDIA_TYPE_VIDEO, 169 CODEC_ID_KGV1, 170 sizeof(KgvContext), 171 decode_init, 172 NULL, 173 decode_end, 174 decode_frame, 175 .long_name = NULL_IF_CONFIG_SMALL("Kega Game Video"), 176}; 177