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avcodec/cllc: Improve creating VLCs 

One can offload the computation of the codes to
ff_init_vlc_from_lengths(); this also improves performance: The number
of decicycles for one call to read_code_table() decreased from 198343
to 148338 with the sample sample-cllc-rgb.avi from the FATE suite; it
has been looped 100 times and the test repeated ten times to test it
sufficiently often.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2020-10-25 00:56:42 +02:00
parent 4df5144102
commit 09062eece2
1 changed files with 3 additions and 11 deletions
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14
libavcodec/cllc.c
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@ -46,11 +46,9 @@ static int read_code_table(CLLCContext *ctx, GetBitContext *gb, VLC *vlc)
{
uint8_t symbols[256];
uint8_t bits[256];
uint16_t codes[256];
int num_lens, num_codes, num_codes_sum, prefix;
int num_lens, num_codes, num_codes_sum;
int i, j, count;
prefix = 0;
count = 0;
num_codes_sum = 0;
@ -74,19 +72,13 @@ static int read_code_table(CLLCContext *ctx, GetBitContext *gb, VLC *vlc)
for (j = 0; j < num_codes; j++) {
symbols[count] = get_bits(gb, 8);
bits[count] = i + 1;
codes[count] = prefix++;
count++;
}
if (prefix > (65535 - 256)/2) {
return AVERROR_INVALIDDATA;
}
prefix <<= 1;
}
return ff_init_vlc_sparse(vlc, VLC_BITS, count, bits, 1, 1,
codes, 2, 2, symbols, 1, 1, 0);
return ff_init_vlc_from_lengths(vlc, VLC_BITS, count, bits, 1,
symbols, 1, 1, 0, 0, ctx->avctx);
}
/*