/*

  * 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 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 "avcodec.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;

 
 typedef struct IdcinContext {
 
     AVCodecContext *avctx;
     AVFrame frame;
 

     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 = 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);
     }
 

     avcodec_get_frame_defaults(&s->frame);

     s->frame.data[0] = NULL;
 
     return 0;
 }
 
 static void idcin_decode_vlcs(IdcinContext *s)
 {

     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 < (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,

                               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);

 
     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);
 

     if (pal) {

         s->frame.palette_has_changed = 1;

         memcpy(s->pal, pal, AVPALETTE_SIZE);

     }

     /* make the palette available on the way out */
     memcpy(s->frame.data[1], s->pal, AVPALETTE_SIZE);

 
     *data_size = sizeof(AVFrame);
     *(AVFrame*)data = s->frame;
 
     /* report that the buffer was completely consumed */
     return buf_size;
 }
 

 static av_cold 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 ff_idcin_decoder = {

     "idcinvideo",

     AVMEDIA_TYPE_VIDEO,

     CODEC_ID_IDCIN,
     sizeof(IdcinContext),
     idcin_decode_init,
     NULL,
     idcin_decode_end,
     idcin_decode_frame,
     CODEC_CAP_DR1,

     .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),

 };