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