Merge remote-tracking branch 'qatar/master'

* qatar/master:
  webp: add a special case for a huffman table with only 1 symbol

Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/webp.c

@@ -277,10 +277,26 @@ static int huff_reader_get_symbol(HuffReader *r, GetBitContext *gb)
 static int huff_reader_build_canonical(HuffReader *r, int *code_lengths,
                                        int alphabet_size)
 {
-    int len, sym, code, ret;
+    int len = 0, sym, code = 0, ret;
     int max_code_length = 0;
     uint16_t *codes;
 
+    /* special-case 1 symbol since the vlc reader cannot handle it */
+    for (sym = 0; sym < alphabet_size; sym++) {
+        if (code_lengths[sym] > 0) {
+            len++;
+            code = sym;
+            if (len > 1)
+                break;
+        }
+    }
+    if (len == 1) {
+        r->nb_symbols = 1;
+        r->simple_symbols[0] = code;
+        r->simple = 1;
+        return 0;
+    }
+
     for (sym = 0; sym < alphabet_size; sym++)
         max_code_length = FFMAX(max_code_length, code_lengths[sym]);