mirror of https://git.ffmpeg.org/ffmpeg.git
Bink: clip AC coefficients during dequantization.
Fixes artefacts with Neverwinter Nights WOTCLogo.bik (http://drmccoy.de/zeugs/WOTCLogo.bik). Fixes trac ticket #352. Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
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@ -571,6 +571,22 @@ static inline int binkb_get_value(BinkContext *c, int bundle_num)
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return ret;
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}
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static inline DCTELEM dequant(DCTELEM in, uint32_t quant, int dc)
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{
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/* Note: multiplication is unsigned but we want signed shift
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* otherwise clipping breaks.
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* TODO: The official decoder does not use clipping at all
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* but instead uses the full 32-bit result.
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* However clipping at least gets rid of the case that a
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* half-black half-white intra block gets black and white swapped
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* and should cause at most minor differences (except for DC). */
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int32_t res = in * quant;
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res >>= 11;
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if (!dc)
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res = av_clip_int16(res);
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return res;
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}
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/**
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* Read 8x8 block of DCT coefficients.
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*
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@ -669,10 +685,10 @@ static int read_dct_coeffs(GetBitContext *gb, DCTELEM block[64], const uint8_t *
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quant = quant_matrices[quant_idx];
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block[0] = (block[0] * quant[0]) >> 11;
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block[0] = dequant(block[0], quant[0], 1);
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for (i = 0; i < coef_count; i++) {
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int idx = coef_idx[i];
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block[scan[idx]] = (block[scan[idx]] * quant[idx]) >> 11;
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block[scan[idx]] = dequant(block[scan[idx]], quant[idx], 0);
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}
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return 0;
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