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ffmpeg / libavcodec / idcinvideo.c @ 2029f312

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/*
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 * Id Quake II CIN Video Decoder
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 * Copyright (C) 2003 the ffmpeg project
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 *
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 * This file is part of FFmpeg.
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 *
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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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 *
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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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 *
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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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 *
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 */
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/**
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 * @file idcinvideo.c
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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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 *
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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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 *
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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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 * tend to be similar.
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 *
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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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 */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "avcodec.h"
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#include "dsputil.h"
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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
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{
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  int count;
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  unsigned char used;
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  int children[2];
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} hnode_t;
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typedef struct IdcinContext {
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    AVCodecContext *avctx;
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    DSPContext dsp;
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    AVFrame frame;
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    unsigned char *buf;
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    int size;
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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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} IdcinContext;
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/*
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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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 * are used.
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 */
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static int huff_smallest_node(hnode_t *hnodes, int num_hnodes) {
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    int i;
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    int best, best_node;
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    best = 99999999;
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    best_node = -1;
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    for(i = 0; i < num_hnodes; i++) {
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        if(hnodes[i].used)
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            continue;
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        if(!hnodes[i].count)
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            continue;
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        if(hnodes[i].count < best) {
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            best = hnodes[i].count;
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            best_node = i;
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        }
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    }
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    if(best_node == -1)
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        return -1;
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    hnodes[best_node].used = 1;
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    return best_node;
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}
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/*
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 * Build the Huffman tree using the generated/loaded probabilities histogram.
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 *
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 * On completion:
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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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 */
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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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     int num_hnodes, i;
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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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        hnodes[i].used = 0;
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    while (1) {
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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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        num_hnodes++;
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    }
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    s->num_huff_nodes[prev] = num_hnodes - 1;
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}
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static int idcin_decode_init(AVCodecContext *avctx)
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{
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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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    s->avctx = avctx;
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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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        return -1;
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    }
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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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    }
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    s->frame.data[0] = NULL;
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    return 0;
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}
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static void idcin_decode_vlcs(IdcinContext *s)
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{
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    hnode_t *hnodes;
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    long x, y;
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    int prev;
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    unsigned char v = 0;
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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(!bit_pos) {
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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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                        return;
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                    }
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                    bit_pos = 8;
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                    v = s->buf[dat_pos++];
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                }
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                node_num = hnodes[node_num].children[v & 0x01];
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                v = v >> 1;
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                bit_pos--;
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            }
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            s->frame.data[0][x] = node_num;
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            prev = node_num;
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        }
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    }
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}
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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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{
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    IdcinContext *s = avctx->priv_data;
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    AVPaletteControl *palette_control = avctx->palctrl;
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    s->buf = buf;
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    s->size = buf_size;
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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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        return -1;
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    }
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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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    }
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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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    return buf_size;
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}
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static int idcin_decode_end(AVCodecContext *avctx)
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{
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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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    return 0;
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}
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AVCodec idcin_decoder = {
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    "idcinvideo",
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    CODEC_TYPE_VIDEO,
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    CODEC_ID_IDCIN,
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    sizeof(IdcinContext),
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    idcin_decode_init,
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    NULL,
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    idcin_decode_end,
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    idcin_decode_frame,
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    CODEC_CAP_DR1,
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};
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