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avcodec/speedhq: Avoid reversing BE codes for LE bitstream reader

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Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2020-10-12 05:59:34 +02:00
parent 9eb7d8b45d
commit 3977aeb78c
1 changed files with 9 additions and 32 deletions
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37
libavcodec/speedhq.c
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@ -558,40 +558,17 @@ static av_cold void compute_alpha_vlcs(void)
level_symbols, 2, 2, 288);
}
static uint32_t reverse(uint32_t num, int bits)
{
return bitswap_32(num) >> (32 - bits);
}
static void reverse_code(const uint16_t *code, const uint8_t *bits,
uint16_t *reversed_code, int num_entries)
{
int i;
for (i = 0; i < num_entries; i++) {
reversed_code[i] = reverse(code[i], bits[i]);
}
}
static av_cold void speedhq_static_init(void)
{
uint16_t ff_mpeg12_vlc_dc_lum_code_reversed[12];
uint16_t ff_mpeg12_vlc_dc_chroma_code_reversed[12];
/* Exactly the same as MPEG-2, except little-endian. */
reverse_code(ff_mpeg12_vlc_dc_lum_code,
ff_mpeg12_vlc_dc_lum_bits,
ff_mpeg12_vlc_dc_lum_code_reversed,
12);
INIT_LE_VLC_STATIC(&dc_lum_vlc_le, DC_VLC_BITS, 12,
/* Exactly the same as MPEG-2, except for a little-endian reader. */
INIT_CUSTOM_VLC_STATIC(&dc_lum_vlc_le, DC_VLC_BITS, 12,
ff_mpeg12_vlc_dc_lum_bits, 1, 1,
ff_mpeg12_vlc_dc_lum_code_reversed, 2, 2, 512);
reverse_code(ff_mpeg12_vlc_dc_chroma_code,
ff_mpeg12_vlc_dc_chroma_bits,
ff_mpeg12_vlc_dc_chroma_code_reversed,
12);
INIT_LE_VLC_STATIC(&dc_chroma_vlc_le, DC_VLC_BITS, 12,
ff_mpeg12_vlc_dc_lum_code, 2, 2,
INIT_VLC_OUTPUT_LE, 512);
INIT_CUSTOM_VLC_STATIC(&dc_chroma_vlc_le, DC_VLC_BITS, 12,
ff_mpeg12_vlc_dc_chroma_bits, 1, 1,
ff_mpeg12_vlc_dc_chroma_code_reversed, 2, 2, 514);
ff_mpeg12_vlc_dc_chroma_code, 2, 2,
INIT_VLC_OUTPUT_LE, 514);
ff_rl_init(&rl_speedhq, speedhq_static_rl_table_store);
INIT_2D_VLC_RL(rl_speedhq, 674, INIT_VLC_LE);