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avcodec/mjpegdec: improve decoding of DNG files 

That have unused symbols coded in DHT.
This commit is contained in:
Paul B Mahol 2020-10-03 14:34:01 +02:00
parent da5b3d0028
commit 1249698e1b
2 changed files with 27 additions and 25 deletions
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15
libavcodec/jpegtables.c
View File

@ -130,25 +130,14 @@ void ff_mjpeg_build_huffman_codes(uint8_t *huff_size, uint16_t *huff_code,
{
int i, j, k,nb, code, sym;
/* Some badly encoded files [1] map 2 different codes to symbol 0.
Only the first one is valid, so we zero-initialize this here and
make sure we only set it once (the first time) in the loop below.
[1]: Embedded JPEGs in "X7 RAW" and "X7 CinemaDNG" samples here:
https://www.dji.com/gr/zenmuse-x7/info#downloads
*/
huff_size[0] = 0;
k = 0;
code = 0;
for(i=1;i<=16;i++) {
nb = bits_table[i];
for(j=0;j<nb;j++) {
sym = val_table[k++];
if (sym != 0 || huff_size[sym] == 0) { /* see comment above */
huff_size[sym] = i;
huff_code[sym] = code;
}
huff_size[sym] = i;
huff_code[sym] = code;
code++;
}
code <<= 1;

37
libavcodec/mjpegdec.c
View File

@ -50,6 +50,21 @@
#include "bytestream.h"
static void build_huffman_codes(uint8_t *huff_size, uint16_t *huff_code,
const uint8_t *bits_table)
{
for (int i = 1, code = 0, k = 0; i <= 16; i++) {
int nb = bits_table[i];
for (int j = 0; j < nb;j++) {
huff_size[k] = i;
huff_code[k] = code;
code++;
k++;
}
code <<= 1;
}
}
static int build_vlc(VLC *vlc, const uint8_t *bits_table,
const uint8_t *val_table, int nb_codes,
int use_static, int is_ac)
@ -61,13 +76,14 @@ static int build_vlc(VLC *vlc, const uint8_t *bits_table,
av_assert0(nb_codes <= 256);
ff_mjpeg_build_huffman_codes(huff_size, huff_code, bits_table, val_table);
build_huffman_codes(huff_size, huff_code, bits_table);
for (i = 0; i < 256; i++)
huff_sym[i] = i + 16 * is_ac;
for (i = 0; i < 256; i++) {
huff_sym[i] = val_table[i] + 16 * is_ac;
if (is_ac)
huff_sym[0] = 16 * 256;
if (is_ac && !val_table[i])
huff_sym[i] = 16 * 256;
}
return ff_init_vlc_sparse(vlc, 9, nb_codes, huff_size, 1, 1,
huff_code, 2, 2, huff_sym, 2, 2, use_static);
@ -240,7 +256,7 @@ int ff_mjpeg_decode_dqt(MJpegDecodeContext *s)
/* decode huffman tables and build VLC decoders */
int ff_mjpeg_decode_dht(MJpegDecodeContext *s)
{
int len, index, i, class, n, v, code_max;
int len, index, i, class, n, v;
uint8_t bits_table[17];
uint8_t val_table[256];
int ret = 0;
@ -270,11 +286,8 @@ int ff_mjpeg_decode_dht(MJpegDecodeContext *s)
if (len < n || n > 256)
return AVERROR_INVALIDDATA;
code_max = 0;
for (i = 0; i < n; i++) {
v = get_bits(&s->gb, 8);
if (v > code_max)
code_max = v;
val_table[i] = v;
}
len -= n;
@ -282,15 +295,15 @@ int ff_mjpeg_decode_dht(MJpegDecodeContext *s)
/* build VLC and flush previous vlc if present */
ff_free_vlc(&s->vlcs[class][index]);
av_log(s->avctx, AV_LOG_DEBUG, "class=%d index=%d nb_codes=%d\n",
class, index, code_max + 1);
class, index, n + 1);
if ((ret = build_vlc(&s->vlcs[class][index], bits_table, val_table,
code_max + 1, 0, class > 0)) < 0)
n + 1, 0, class > 0)) < 0)
return ret;
if (class > 0) {
ff_free_vlc(&s->vlcs[2][index]);
if ((ret = build_vlc(&s->vlcs[2][index], bits_table, val_table,
code_max + 1, 0, 0)) < 0)
n + 1, 0, 0)) < 0)
return ret;
}