+/**
+ * Comparator - our nodes should ascend by count
+ * but with preserved symbol order
+ */
+static int huff_cmp(const Node *a, const Node *b){
+ return (a->count - b->count)*256 + a->sym - b->sym;
+}
+
+static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t *xlat, Node *nodes, int node, uint32_t pfx, int pl, int *pos)
+{
+ int s;
+
+ s = nodes[node].sym;
+ if(s != HNODE || !nodes[node].count){
+ bits[*pos] = pfx;
+ lens[*pos] = pl;
+ xlat[*pos] = s;
+ (*pos)++;
+ }else{
+ pfx <<= 1;
+ pl++;
+ get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl, pos);
+ pfx |= 1;
+ get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0+1, pfx, pl, pos);
+ }
+}
+
+static int build_huff_tree(VLC *vlc, Node *nodes, uint8_t *xlat)
+{
+ uint32_t bits[256];
+ int16_t lens[256];
+ int pos = 0;
+
+ get_tree_codes(bits, lens, xlat, nodes, 510, 0, 0, &pos);
+ return init_vlc(vlc, 9, pos, lens, 2, 2, bits, 4, 4, 0);
+}
+
+
+/**
+ * decode Fraps v2 packed plane
+ */
+static int fraps2_decode_plane(FrapsContext *s, uint8_t *dst, int stride, int w,
+ int h, uint8_t *src, int size, int Uoff)
+{
+ int i, j;
+ int cur_node;
+ GetBitContext gb;
+ VLC vlc;
+ int64_t sum = 0;
+ uint8_t recode[256];
+
+ for(i = 0; i < 256; i++){
+ s->nodes[i].sym = i;
+ s->nodes[i].count = AV_RL32(src);
+ s->nodes[i].n0 = -2;
+ if(s->nodes[i].count < 0) {
+ av_log(s->avctx, AV_LOG_ERROR, "Symbol count < 0\n");
+ return -1;
+ }
+ src += 4;
+ sum += s->nodes[i].count;
+ }
+ size -= 1024;
+
+ if(sum >> 31) {
+ av_log(s->avctx, AV_LOG_ERROR, "Too high symbol frequencies. Tree construction is not possible\n");
+ return -1;
+ }
+ qsort(s->nodes, 256, sizeof(Node), huff_cmp);
+ cur_node = 256;
+ for(i = 0; i < 511; i += 2){
+ s->nodes[cur_node].sym = HNODE;
+ s->nodes[cur_node].count = s->nodes[i].count + s->nodes[i+1].count;
+ s->nodes[cur_node].n0 = i;
+ for(j = cur_node; j > 0; j--){
+ if(s->nodes[j].count >= s->nodes[j - 1].count) break;
+ FFSWAP(Node, s->nodes[j], s->nodes[j - 1]);
+ }
+ cur_node++;
+ }
+ if(build_huff_tree(&vlc, s->nodes, recode) < 0){
+ av_log(s->avctx, AV_LOG_ERROR, "Error building tree\n");
+ return -1;
+ }
+ /* we have built Huffman table and are ready to decode plane */
+
+ /* convert bits so they may be used by standard bitreader */
+ s->dsp.bswap_buf(s->tmpbuf, src, size >> 2);
+
+ init_get_bits(&gb, s->tmpbuf, size * 8);
+ for(j = 0; j < h; j++){
+ for(i = 0; i < w; i++){
+ dst[i] = recode[get_vlc2(&gb, vlc.table, 9, 3)];
+ /* lines are stored as deltas between previous lines
+ * and we need to add 0x80 to the first lines of chroma planes
+ */
+ if(j) dst[i] += dst[i - stride];
+ else if(Uoff) dst[i] += 0x80;
+ }
+ dst += stride;
+ }
+ free_vlc(&vlc);
+ return 0;
+}