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libavcodec/idcinvideo.c

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00001 /*
00002  * id Quake II CIN Video Decoder
00003  * Copyright (C) 2003 the ffmpeg project
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 
00047 #include <stdio.h>
00048 #include <stdlib.h>
00049 #include <string.h>
00050 #include <unistd.h>
00051 
00052 #include "avcodec.h"
00053 
00054 #define HUFFMAN_TABLE_SIZE 64 * 1024
00055 #define HUF_TOKENS 256
00056 #define PALETTE_COUNT 256
00057 
00058 typedef struct
00059 {
00060   int count;
00061   unsigned char used;
00062   int children[2];
00063 } hnode;
00064 
00065 typedef struct IdcinContext {
00066 
00067     AVCodecContext *avctx;
00068     AVFrame frame;
00069 
00070     const unsigned char *buf;
00071     int size;
00072 
00073     hnode huff_nodes[256][HUF_TOKENS*2];
00074     int num_huff_nodes[256];
00075 
00076 } IdcinContext;
00077 
00078 /*
00079  * Find the lowest probability node in a Huffman table, and mark it as
00080  * being assigned to a higher probability.
00081  * Returns the node index of the lowest unused node, or -1 if all nodes
00082  * are used.
00083  */
00084 static int huff_smallest_node(hnode *hnodes, int num_hnodes) {
00085     int i;
00086     int best, best_node;
00087 
00088     best = 99999999;
00089     best_node = -1;
00090     for(i = 0; i < num_hnodes; i++) {
00091         if(hnodes[i].used)
00092             continue;
00093         if(!hnodes[i].count)
00094             continue;
00095         if(hnodes[i].count < best) {
00096             best = hnodes[i].count;
00097             best_node = i;
00098         }
00099     }
00100 
00101     if(best_node == -1)
00102         return -1;
00103     hnodes[best_node].used = 1;
00104     return best_node;
00105 }
00106 
00107 /*
00108  * Build the Huffman tree using the generated/loaded probabilities histogram.
00109  *
00110  * On completion:
00111  *  huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree.
00112  *  huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree.
00113  *  num_huff_nodes[prev] - contains the index to the root node of the tree.
00114  *    That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node.
00115  */
00116 static av_cold void huff_build_tree(IdcinContext *s, int prev) {
00117     hnode *node, *hnodes;
00118      int num_hnodes, i;
00119 
00120     num_hnodes = HUF_TOKENS;
00121     hnodes = s->huff_nodes[prev];
00122     for(i = 0; i < HUF_TOKENS * 2; i++)
00123         hnodes[i].used = 0;
00124 
00125     while (1) {
00126         node = &hnodes[num_hnodes];             /* next free node */
00127 
00128         /* pick two lowest counts */
00129         node->children[0] = huff_smallest_node(hnodes, num_hnodes);
00130         if(node->children[0] == -1)
00131             break;      /* reached the root node */
00132 
00133         node->children[1] = huff_smallest_node(hnodes, num_hnodes);
00134         if(node->children[1] == -1)
00135             break;      /* reached the root node */
00136 
00137         /* combine nodes probability for new node */
00138         node->count = hnodes[node->children[0]].count +
00139         hnodes[node->children[1]].count;
00140         num_hnodes++;
00141     }
00142 
00143     s->num_huff_nodes[prev] = num_hnodes - 1;
00144 }
00145 
00146 static av_cold int idcin_decode_init(AVCodecContext *avctx)
00147 {
00148     IdcinContext *s = avctx->priv_data;
00149     int i, j, histogram_index = 0;
00150     unsigned char *histograms;
00151 
00152     s->avctx = avctx;
00153     avctx->pix_fmt = PIX_FMT_PAL8;
00154 
00155     /* make sure the Huffman tables make it */
00156     if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {
00157         av_log(s->avctx, AV_LOG_ERROR, "  id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);
00158         return -1;
00159     }
00160 
00161     /* build the 256 Huffman decode trees */
00162     histograms = (unsigned char *)s->avctx->extradata;
00163     for (i = 0; i < 256; i++) {
00164         for(j = 0; j < HUF_TOKENS; j++)
00165             s->huff_nodes[i][j].count = histograms[histogram_index++];
00166         huff_build_tree(s, i);
00167     }
00168 
00169     s->frame.data[0] = NULL;
00170 
00171     return 0;
00172 }
00173 
00174 static void idcin_decode_vlcs(IdcinContext *s)
00175 {
00176     hnode *hnodes;
00177     long x, y;
00178     int prev;
00179     unsigned char v = 0;
00180     int bit_pos, node_num, dat_pos;
00181 
00182     prev = bit_pos = dat_pos = 0;
00183     for (y = 0; y < (s->frame.linesize[0] * s->avctx->height);
00184         y += s->frame.linesize[0]) {
00185         for (x = y; x < y + s->avctx->width; x++) {
00186             node_num = s->num_huff_nodes[prev];
00187             hnodes = s->huff_nodes[prev];
00188 
00189             while(node_num >= HUF_TOKENS) {
00190                 if(!bit_pos) {
00191                     if(dat_pos >= s->size) {
00192                         av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");
00193                         return;
00194                     }
00195                     bit_pos = 8;
00196                     v = s->buf[dat_pos++];
00197                 }
00198 
00199                 node_num = hnodes[node_num].children[v & 0x01];
00200                 v = v >> 1;
00201                 bit_pos--;
00202             }
00203 
00204             s->frame.data[0][x] = node_num;
00205             prev = node_num;
00206         }
00207     }
00208 }
00209 
00210 static int idcin_decode_frame(AVCodecContext *avctx,
00211                               void *data, int *data_size,
00212                               const uint8_t *buf, int buf_size)
00213 {
00214     IdcinContext *s = avctx->priv_data;
00215     AVPaletteControl *palette_control = avctx->palctrl;
00216 
00217     s->buf = buf;
00218     s->size = buf_size;
00219 
00220     if (s->frame.data[0])
00221         avctx->release_buffer(avctx, &s->frame);
00222 
00223     if (avctx->get_buffer(avctx, &s->frame)) {
00224         av_log(avctx, AV_LOG_ERROR, "  id CIN Video: get_buffer() failed\n");
00225         return -1;
00226     }
00227 
00228     idcin_decode_vlcs(s);
00229 
00230     /* make the palette available on the way out */
00231     memcpy(s->frame.data[1], palette_control->palette, PALETTE_COUNT * 4);
00232     /* If palette changed inform application*/
00233     if (palette_control->palette_changed) {
00234         palette_control->palette_changed = 0;
00235         s->frame.palette_has_changed = 1;
00236     }
00237 
00238     *data_size = sizeof(AVFrame);
00239     *(AVFrame*)data = s->frame;
00240 
00241     /* report that the buffer was completely consumed */
00242     return buf_size;
00243 }
00244 
00245 static av_cold int idcin_decode_end(AVCodecContext *avctx)
00246 {
00247     IdcinContext *s = avctx->priv_data;
00248 
00249     if (s->frame.data[0])
00250         avctx->release_buffer(avctx, &s->frame);
00251 
00252     return 0;
00253 }
00254 
00255 AVCodec idcin_decoder = {
00256     "idcinvideo",
00257     CODEC_TYPE_VIDEO,
00258     CODEC_ID_IDCIN,
00259     sizeof(IdcinContext),
00260     idcin_decode_init,
00261     NULL,
00262     idcin_decode_end,
00263     idcin_decode_frame,
00264     CODEC_CAP_DR1,
00265     .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
00266 };
00267 

Generated on Sat Feb 16 2013 09:23:12 for ffmpeg by  doxygen 1.7.1