From d085f80fa1381b363b0b91689407d5646d78ed28 Mon Sep 17 00:00:00 2001 From: Justin Ruggles Date: Wed, 4 Dec 2013 16:53:18 -0500 Subject: webp: add a special case for a huffman table with only 1 symbol The vlc reader cannot handle 0-bit huffman codes. For most situations WebP uses the "simple" huffman coding for this case, but that will only handle symbols up to 255. For the LZ77 distance codes, larger symbol values are needed, so it can happen in rare cases that a normal huffman table is used that only has a single symbol. --- libavcodec/webp.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'libavcodec/webp.c') diff --git a/libavcodec/webp.c b/libavcodec/webp.c index d531a78a39..f9f8bfcbff 100644 --- a/libavcodec/webp.c +++ b/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]); -- cgit v1.2.3