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avcodec/mjpegdec: Simplify creating VLC table

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ff_init_vlc_from_lengths() can be used to offload the computation
of the codes; it also allows to omit the check whether the codes
are already properly ordered (they are).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2020-11-01 03:01:05 +01:00
parent d4a4a6747d
commit cd7c3ac84d
1 changed files with 9 additions and 14 deletions
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23
libavcodec/mjpegdec.c
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@ -50,33 +50,28 @@
#include "bytestream.h" #include "bytestream.h"
static void build_huffman_codes(uint8_t *huff_size, uint16_t *huff_code, static void build_huffman_codes(uint8_t *huff_size, const uint8_t *bits_table)
const uint8_t *bits_table)
{ {
for (int i = 1, code = 0, k = 0; i <= 16; i++) { for (int i = 1, k = 0; i <= 16; i++) {
int nb = bits_table[i]; int nb = bits_table[i];
for (int j = 0; j < nb;j++) { for (int j = 0; j < nb;j++) {
huff_size[k] = i; huff_size[k] = i;
huff_code[k] = code;
code++;
k++; k++;
} }
code <<= 1;
} }
} }
static int build_vlc(VLC *vlc, const uint8_t *bits_table, static int build_vlc(VLC *vlc, const uint8_t *bits_table,
const uint8_t *val_table, int nb_codes, const uint8_t *val_table, int nb_codes,
int is_ac) int is_ac, void *logctx)
{ {
uint8_t huff_size[256]; uint8_t huff_size[256];
uint16_t huff_code[256];
uint16_t huff_sym[256]; uint16_t huff_sym[256];
int i; int i;
av_assert0(nb_codes <= 256); av_assert0(nb_codes <= 256);
build_huffman_codes(huff_size, huff_code, bits_table); build_huffman_codes(huff_size, bits_table);
for (i = 0; i < nb_codes; i++) { for (i = 0; i < nb_codes; i++) {
huff_sym[i] = val_table[i] + 16 * is_ac; huff_sym[i] = val_table[i] + 16 * is_ac;
@ -85,8 +80,8 @@ static int build_vlc(VLC *vlc, const uint8_t *bits_table,
huff_sym[i] = 16 * 256; huff_sym[i] = 16 * 256;
} }
return ff_init_vlc_sparse(vlc, 9, nb_codes, huff_size, 1, 1, return ff_init_vlc_from_lengths(vlc, 9, nb_codes, huff_size, 1,
huff_code, 2, 2, huff_sym, 2, 2, 0); huff_sym, 2, 2, 0, 0, logctx);
} }
static int init_default_huffman_tables(MJpegDecodeContext *s) static int init_default_huffman_tables(MJpegDecodeContext *s)
@ -116,7 +111,7 @@ static int init_default_huffman_tables(MJpegDecodeContext *s)
for (i = 0; i < FF_ARRAY_ELEMS(ht); i++) { for (i = 0; i < FF_ARRAY_ELEMS(ht); i++) {
ret = build_vlc(&s->vlcs[ht[i].class][ht[i].index], ret = build_vlc(&s->vlcs[ht[i].class][ht[i].index],
ht[i].bits, ht[i].values, ht[i].length, ht[i].bits, ht[i].values, ht[i].length,
ht[i].class == 1); ht[i].class == 1, s->avctx);
if (ret < 0) if (ret < 0)
return ret; return ret;
@ -296,13 +291,13 @@ int ff_mjpeg_decode_dht(MJpegDecodeContext *s)
av_log(s->avctx, AV_LOG_DEBUG, "class=%d index=%d nb_codes=%d\n", av_log(s->avctx, AV_LOG_DEBUG, "class=%d index=%d nb_codes=%d\n",
class, index, n); class, index, n);
if ((ret = build_vlc(&s->vlcs[class][index], bits_table, val_table, if ((ret = build_vlc(&s->vlcs[class][index], bits_table, val_table,
n, class > 0)) < 0) n, class > 0, s->avctx)) < 0)
return ret; return ret;
if (class > 0) { if (class > 0) {
ff_free_vlc(&s->vlcs[2][index]); ff_free_vlc(&s->vlcs[2][index]);
if ((ret = build_vlc(&s->vlcs[2][index], bits_table, val_table, if ((ret = build_vlc(&s->vlcs[2][index], bits_table, val_table,
n, 0)) < 0) n, 0, s->avctx)) < 0)
return ret; return ret;
} }