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FFmpeg/libavcodec/idcinvideo.c
Andreas Rheinhardt a247ac640d avcodec: Constify AVCodecs
Given that the AVCodec.next pointer has now been removed, most of the
AVCodecs are not modified at all any more and can therefore be made
const (as this patch does); the only exceptions are the very few codecs
for external libraries that have a init_static_data callback.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>
2021-04-27 10:43:15 -03:00

257 lines
7.6 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
* 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 "decode.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;
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;
frame->palette_has_changed = ff_copy_palette(s->pal, avpkt, avctx);
/* 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;
}
static const AVCodecDefault idcin_defaults[] = {
{ "max_pixels", "320*240" },
{ NULL },
};
const 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,
.defaults = idcin_defaults,
.caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,
};