FFmpeg

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Jun Zhao 24f296c7a1 lavc/hevc: optimize dequant for shift=0 case (identity transform)

The HEVC dequantization uses:
  shift = 15 - bit_depth - log2_size

When shift equals 0, the operation becomes an identity transform:
  - For shift > 0: output = (input + offset) >> shift
  - For shift < 0: output = input << (-shift)
  - For shift = 0: output = input << 0 = input (no change)

This occurs in the following cases:
  - 10-bit, 32x32 block: shift = 15 - 10 - 5 = 0
  - 12-bit, 8x8 block:   shift = 15 - 12 - 3 = 0

Previously, the code would still iterate through all coefficients
and perform redundant read-modify-write operations even when shift=0.

This patch adds an early return for shift=0, avoiding unnecessary
memory operations. checkasm benchmarks on Apple M4 show:
  - 10-bit 32x32: 69.1 -> 1.6 cycles (43x faster)
  - 12-bit 8x8:   30.9 -> 1.7 cycles (18x faster)

Signed-off-by: Jun Zhao <barryjzhao@tencent.com>

2026-01-25 06:55:26 +00:00

cabac.c

all: fix whitespace/new-line issues

2025-08-03 13:48:47 +02:00

data.c

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data.h

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dsp_template.c

lavc/hevc: optimize dequant for shift=0 case (identity transform)

2026-01-25 06:55:26 +00:00

dsp.c