ffmpeg/libavcodec/idcinvideo.c

270 lines
7.7 KiB
C

/*
* 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 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 <unistd.h>
#include "avcodec.h"
#include "dsputil.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_t;
typedef struct IdcinContext {
AVCodecContext *avctx;
DSPContext dsp;
AVFrame frame;
const unsigned char *buf;
int size;
hnode_t 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_t *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 void huff_build_tree(IdcinContext *s, int prev) {
hnode_t *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 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;
dsputil_init(&s->dsp, avctx);
/* 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_t *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,
const uint8_t *buf, int buf_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 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",
CODEC_TYPE_VIDEO,
CODEC_ID_IDCIN,
sizeof(IdcinContext),
idcin_decode_init,
NULL,
idcin_decode_end,
idcin_decode_frame,
CODEC_CAP_DR1,
};