/* * id Quake II CIN Video Decoder * Copyright (C) 2003 the ffmpeg project * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file libavcodec/idcinvideo.c * id Quake II Cin Video Decoder by Dr. Tim Ferguson * For more information about the id CIN format, visit: * http://www.csse.monash.edu.au/~timf/ * * This video decoder outputs PAL8 colorspace data. Interacting with this * decoder is a little involved. During initialization, the demuxer must * transmit the 65536-byte Huffman table(s) to the decoder via extradata. * Then, whenever a palette change is encountered while demuxing the file, * the demuxer must use the same extradata space to transmit an * AVPaletteControl structure. * * id CIN video is purely Huffman-coded, intraframe-only codec. It achieves * a little more compression by exploiting the fact that adjacent pixels * tend to be similar. * * Note that this decoder could use ffmpeg's optimized VLC facilities * rather than naive, tree-based Huffman decoding. However, there are 256 * Huffman tables. Plus, the VLC bit coding order is right -> left instead * or left -> right, so all of the bits would have to be reversed. Further, * the original Quake II implementation likely used a similar naive * decoding algorithm and it worked fine on much lower spec machines. */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include "avcodec.h" #define HUFFMAN_TABLE_SIZE 64 * 1024 #define HUF_TOKENS 256 #define PALETTE_COUNT 256 typedef struct { int count; unsigned char used; int children[2]; } hnode; typedef struct IdcinContext { AVCodecContext *avctx; AVFrame frame; const unsigned char *buf; int size; hnode huff_nodes[256][HUF_TOKENS*2]; int num_huff_nodes[256]; } IdcinContext; /* * Find the lowest probability node in a Huffman table, and mark it as * being assigned to a higher probability. * Returns the node index of the lowest unused node, or -1 if all nodes * are used. */ static int huff_smallest_node(hnode *hnodes, int num_hnodes) { int i; int best, best_node; best = 99999999; best_node = -1; for(i = 0; i < num_hnodes; i++) { if(hnodes[i].used) continue; if(!hnodes[i].count) continue; if(hnodes[i].count < best) { best = hnodes[i].count; best_node = i; } } if(best_node == -1) return -1; hnodes[best_node].used = 1; return best_node; } /* * Build the Huffman tree using the generated/loaded probabilities histogram. * * On completion: * huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree. * huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree. * num_huff_nodes[prev] - contains the index to the root node of the tree. * That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node. */ static av_cold void huff_build_tree(IdcinContext *s, int prev) { hnode *node, *hnodes; int num_hnodes, i; num_hnodes = HUF_TOKENS; hnodes = s->huff_nodes[prev]; for(i = 0; i < HUF_TOKENS * 2; i++) hnodes[i].used = 0; while (1) { node = &hnodes[num_hnodes]; /* next free node */ /* pick two lowest counts */ node->children[0] = huff_smallest_node(hnodes, num_hnodes); if(node->children[0] == -1) break; /* reached the root node */ node->children[1] = huff_smallest_node(hnodes, num_hnodes); if(node->children[1] == -1) break; /* reached the root node */ /* combine nodes probability for new node */ node->count = hnodes[node->children[0]].count + hnodes[node->children[1]].count; num_hnodes++; } s->num_huff_nodes[prev] = num_hnodes - 1; } static av_cold int idcin_decode_init(AVCodecContext *avctx) { IdcinContext *s = avctx->priv_data; int i, j, histogram_index = 0; unsigned char *histograms; s->avctx = avctx; avctx->pix_fmt = PIX_FMT_PAL8; /* make sure the Huffman tables make it */ if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) { av_log(s->avctx, AV_LOG_ERROR, " id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE); return -1; } /* build the 256 Huffman decode trees */ histograms = (unsigned char *)s->avctx->extradata; for (i = 0; i < 256; i++) { for(j = 0; j < HUF_TOKENS; j++) s->huff_nodes[i][j].count = histograms[histogram_index++]; huff_build_tree(s, i); } s->frame.data[0] = NULL; return 0; } static void idcin_decode_vlcs(IdcinContext *s) { hnode *hnodes; long x, y; int prev; unsigned char v = 0; int bit_pos, node_num, dat_pos; prev = bit_pos = dat_pos = 0; for (y = 0; y < (s->frame.linesize[0] * s->avctx->height); y += s->frame.linesize[0]) { for (x = y; x < y + s->avctx->width; x++) { node_num = s->num_huff_nodes[prev]; hnodes = s->huff_nodes[prev]; while(node_num >= HUF_TOKENS) { if(!bit_pos) { if(dat_pos >= s->size) { av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n"); return; } bit_pos = 8; v = s->buf[dat_pos++]; } node_num = hnodes[node_num].children[v & 0x01]; v = v >> 1; bit_pos--; } s->frame.data[0][x] = node_num; prev = node_num; } } } static int idcin_decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt) { const uint8_t *buf = avpkt->data; int buf_size = avpkt->size; IdcinContext *s = avctx->priv_data; AVPaletteControl *palette_control = avctx->palctrl; s->buf = buf; s->size = buf_size; if (s->frame.data[0]) avctx->release_buffer(avctx, &s->frame); if (avctx->get_buffer(avctx, &s->frame)) { av_log(avctx, AV_LOG_ERROR, " id CIN Video: get_buffer() failed\n"); return -1; } idcin_decode_vlcs(s); /* make the palette available on the way out */ memcpy(s->frame.data[1], palette_control->palette, PALETTE_COUNT * 4); /* If palette changed inform application*/ if (palette_control->palette_changed) { palette_control->palette_changed = 0; s->frame.palette_has_changed = 1; } *data_size = sizeof(AVFrame); *(AVFrame*)data = s->frame; /* report that the buffer was completely consumed */ return buf_size; } static av_cold int idcin_decode_end(AVCodecContext *avctx) { IdcinContext *s = avctx->priv_data; if (s->frame.data[0]) avctx->release_buffer(avctx, &s->frame); return 0; } AVCodec idcin_decoder = { "idcinvideo", AVMEDIA_TYPE_VIDEO, CODEC_ID_IDCIN, sizeof(IdcinContext), idcin_decode_init, NULL, idcin_decode_end, idcin_decode_frame, CODEC_CAP_DR1, .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"), };