/*
* 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
* 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 libavcodec'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"
#include "internal.h"
#include "libavutil/internal.h"
#define HUFFMAN_TABLE_SIZE 64 * 1024
#define HUF_TOKENS 256
#define PALETTE_COUNT 256
typedef struct hnode {
int count;
unsigned char used;
int children[2];
} hnode;
typedef struct IdcinContext {
AVCodecContext *avctx;
const unsigned char *buf;
int size;
hnode huff_nodes[256][HUF_TOKENS*2];
int num_huff_nodes[256];
uint32_t pal[256];
} IdcinContext;
/**
* Find the lowest probability node in a Huffman table, and mark it as
* being assigned to a higher probability.
* @return 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 = AV_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);
}
return 0;
}
static int idcin_decode_vlcs(IdcinContext *s, AVFrame *frame)
{
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 < (frame->linesize[0] * s->avctx->height);
y += 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 -1;
}
bit_pos = 8;
v = s->buf[dat_pos++];
}
node_num = hnodes[node_num].children[v & 0x01];
v = v >> 1;
bit_pos--;
}
frame->data[0][x] = node_num;
prev = node_num;
}
}
return 0;
}
static int idcin_decode_frame(AVCodecContext *avctx,
void *data, int *got_frame,
AVPacket *avpkt)
{
const uint8_t *buf = avpkt->data;
int buf_size = avpkt->size;
IdcinContext *s = avctx->priv_data;
const uint8_t *pal = av_packet_get_side_data(avpkt, AV_PKT_DATA_PALETTE, NULL);
AVFrame *frame = data;
int ret;
s->buf = buf;
s->size = buf_size;
if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
return ret;
if (idcin_decode_vlcs(s, frame))
return AVERROR_INVALIDDATA;
if (pal) {
frame->palette_has_changed = 1;
memcpy(s
->pal
, pal
, AVPALETTE_SIZE
); }
/* make the palette available on the way out */
memcpy(frame
->data
[1], s
->pal
, AVPALETTE_SIZE
);
*got_frame = 1;
/* report that the buffer was completely consumed */
return buf_size;
}
AVCodec ff_idcin_decoder = {
.name = "idcinvideo",
.long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
.type = AVMEDIA_TYPE_VIDEO,
.id = AV_CODEC_ID_IDCIN,
.priv_data_size = sizeof(IdcinContext),
.init = idcin_decode_init,
.decode = idcin_decode_frame,
.capabilities = AV_CODEC_CAP_DR1,
};