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avcodec/rv34: Simplify getting right VLC

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For both RealVideo 3.0 as well as RealVideo 4.0 the VLC table to use
depends upon the slice's quantization parameter; these are coded on five
bits in the bitstream and are therefore in the range of 0..31; yet the
last element here is not valid and therefore the quantizer is clipped to
the range 0..30 to get the index. But this is unnecessary: One can just
add one element more to the relevant array to avoid the clipping.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2020-10-22 12:02:11 +02:00
parent f033e6d2e6
commit 3a836f38f6
2 changed files with 8 additions and 6 deletions
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6
libavcodec/rv34.c
View File

@ -24,6 +24,7 @@
* RV30/40 decoder common data
*/
#include "libavutil/avassert.h"
#include "libavutil/imgutils.h"
#include "libavutil/internal.h"
@ -339,8 +340,9 @@ static inline RV34VLC* choose_vlc_set(int quant, int mod, int type)
{
if(mod == 2 && quant < 19) quant += 10;
else if(mod && quant < 26) quant += 5;
return type ? &inter_vlcs[rv34_quant_to_vlc_set[1][av_clip(quant, 0, 30)]]
: &intra_vlcs[rv34_quant_to_vlc_set[0][av_clip(quant, 0, 30)]];
av_assert2(quant >= 0 && quant < 32);
return type ? &inter_vlcs[rv34_quant_to_vlc_set[1][quant]]
: &intra_vlcs[rv34_quant_to_vlc_set[0][quant]];
}
/**

8
libavcodec/rv34data.h
View File

@ -90,13 +90,13 @@ static const uint16_t rv34_qscale_tab[32] = {
/**
* tables used to translate a quantizer value into a VLC set for decoding
* The first table is used for intraframes.
* The first table is used for intraframes. The two last entries are invalid.
*/
static const uint8_t rv34_quant_to_vlc_set[2][31] = {
static const uint8_t rv34_quant_to_vlc_set[2][32] = {
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1,
2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 0 },
2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 0, 0 },
{ 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3,
3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6 },
3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 6 },
};
/**