The branch, master has been updated
via 1c5bb1b12da142ae111b35565420ffd1ccc9a029 (commit)
via 1982add48595db4891b16131928b9eb25fb85e2f (commit)
from 04eeaeed11d721ccbcd0104c2e79e3ceb819585d (commit)
- Log -----------------------------------------------------------------
commit 1c5bb1b12da142ae111b35565420ffd1ccc9a029
Author: averne <[email protected]>
AuthorDate: Sat Nov 29 17:25:17 2025 +0100
Commit: averne <[email protected]>
CommitDate: Sat Nov 29 17:56:28 2025 +0100
vulkan/prores: normalize coefficients during IDCT
This allows increased internal precision.
In addition, we can introduce an offset to the DC coefficient
during the second IDCT step, to remove a per-element addition
in the output codepath.
Finally, by processing columns first we can remove the barrier
after loading coefficients.
Signed-off-by: averne <[email protected]>
diff --git a/libavcodec/vulkan/prores_idct.comp
b/libavcodec/vulkan/prores_idct.comp
index 5d0d41cfa5..5eef61e57a 100644
--- a/libavcodec/vulkan/prores_idct.comp
+++ b/libavcodec/vulkan/prores_idct.comp
@@ -37,19 +37,27 @@ void put_px(uint tex_idx, ivec2 pos, uint v)
#endif
}
-const float idct_8x8_scales[] = {
- 0.353553390593274f, // cos(4 * pi/16) / 2
- 0.490392640201615f, // cos(1 * pi/16) / 2
- 0.461939766255643f, // cos(2 * pi/16) / 2
- 0.415734806151273f, // cos(3 * pi/16) / 2
- 0.353553390593274f, // cos(4 * pi/16) / 2
- 0.277785116509801f, // cos(5 * pi/16) / 2
- 0.191341716182545f, // cos(6 * pi/16) / 2
- 0.097545161008064f, // cos(7 * pi/16) / 2
+const float idct_scale[64] = {
+ 0.1250000000000000, 0.1733799806652684, 0.1633203706095471,
0.1469844503024199,
+ 0.1250000000000000, 0.0982118697983878, 0.0676495125182746,
0.0344874224103679,
+ 0.1733799806652684, 0.2404849415639108, 0.2265318615882219,
0.2038732892122293,
+ 0.1733799806652684, 0.1362237766939547, 0.0938325693794663,
0.0478354290456362,
+ 0.1633203706095471, 0.2265318615882219, 0.2133883476483184,
0.1920444391778541,
+ 0.1633203706095471, 0.1283199917898342, 0.0883883476483185,
0.0450599888754343,
+ 0.1469844503024199, 0.2038732892122293, 0.1920444391778541,
0.1728354290456362,
+ 0.1469844503024199, 0.1154849415639109, 0.0795474112858021,
0.0405529186026822,
+ 0.1250000000000000, 0.1733799806652684, 0.1633203706095471,
0.1469844503024199,
+ 0.1250000000000000, 0.0982118697983878, 0.0676495125182746,
0.0344874224103679,
+ 0.0982118697983878, 0.1362237766939547, 0.1283199917898342,
0.1154849415639109,
+ 0.0982118697983878, 0.0771645709543638, 0.0531518809229535,
0.0270965939155924,
+ 0.0676495125182746, 0.0938325693794663, 0.0883883476483185,
0.0795474112858021,
+ 0.0676495125182746, 0.0531518809229535, 0.0366116523516816,
0.0186644585125857,
+ 0.0344874224103679, 0.0478354290456362, 0.0450599888754343,
0.0405529186026822,
+ 0.0344874224103679, 0.0270965939155924, 0.0186644585125857,
0.0095150584360892,
};
/* 7.4 Inverse Transform */
-void idct(uint block, uint offset, uint stride)
+void idct8(uint block, uint offset, uint stride)
{
float t0, t1, t2, t3, t4, t5, t6, t7, u8;
float u0, u1, u2, u3, u4, u5, u6, u7;
@@ -117,6 +125,12 @@ void main(void)
uint chroma_shift = comp != 0 ? log2_chroma_w : 0;
bool act = gid.x < mb_width << (4 - chroma_shift);
+ /**
+ * Normalize coefficients to [-1, 1] for increased precision during the
iDCT.
+ * DCT coeffs have the range of a 12-bit signed integer (7.4 Inverse
Transform).
+ */
+ const float norm = 1.0f / (1 << 11);
+
/* Coalesced load of DCT coeffs in shared memory, inverse quantization */
if (act) {
/**
@@ -131,28 +145,31 @@ void main(void)
int qscale = qidx > 128 ? (qidx - 96) << 2 : qidx;
[[unroll]] for (uint i = 0; i < 8; ++i) {
+ uint cidx = (i << 3) + idx;
int c = sign_extend(int(get_px(comp, ivec2(gid.x, (gid.y << 3) +
i))), 16);
- float v = float(c * qscale * int(qmat[(i << 3) + idx]));
- blocks[block][i * 9 + idx] = v * idct_8x8_scales[idx] *
idct_8x8_scales[i];
+ float v = float(c * qscale * int(qmat[cidx])) * norm;
+ blocks[block][i * 9 + idx] = v * idct_scale[cidx];
}
}
- /* Row-wise iDCT */
+ /* Column-wise iDCT */
+ idct8(block, idx, 9);
barrier();
- idct(block, idx * 9, 1);
- /* Column-wise iDCT */
+ /* Remap [-1, 1] to [0, 2] to remove a per-element addition in the output
loop */
+ blocks[block][idx * 9] += 1.0f;
+
+ /* Row-wise iDCT */
+ idct8(block, idx * 9, 1);
barrier();
- idct(block, idx, 9);
- float fact = 1.0f / (1 << (12 - depth)), off = 1 << (depth - 1);
+ float fact = 1 << (depth - 1);
int maxv = (1 << depth) - 1;
/* 7.5.1 Color Component Samples. Rescale, clamp and write back to global
memory */
- barrier();
if (act) {
[[unroll]] for (uint i = 0; i < 8; ++i) {
- float v = round(blocks[block][i * 9 + idx] * fact + off);
+ float v = round(blocks[block][i * 9 + idx] * fact);
put_px(comp, ivec2(gid.x, (gid.y << 3) + i), clamp(int(v), 0,
maxv));
}
}
commit 1982add48595db4891b16131928b9eb25fb85e2f
Author: averne <[email protected]>
AuthorDate: Sat Nov 29 17:26:51 2025 +0100
Commit: averne <[email protected]>
CommitDate: Sat Nov 29 17:27:21 2025 +0100
vulkan/prores: fix dequantization for 4:2:2 subsampling
Bug introduced in d00f41f due to an oversight.
diff --git a/libavcodec/vulkan/prores_idct.comp
b/libavcodec/vulkan/prores_idct.comp
index 05ba8e4967..5d0d41cfa5 100644
--- a/libavcodec/vulkan/prores_idct.comp
+++ b/libavcodec/vulkan/prores_idct.comp
@@ -127,7 +127,7 @@ void main(void)
uint8_t[64] qmat = comp == 0 ? qmat_luma : qmat_chroma;
/* Table 15 */
- uint8_t qidx = quant_idx[(gid.y >> 1) * mb_width + (gid.x >> 4)];
+ uint8_t qidx = quant_idx[(gid.y >> 1) * mb_width + (gid.x >> (4 -
chroma_shift))];
int qscale = qidx > 128 ? (qidx - 96) << 2 : qidx;
[[unroll]] for (uint i = 0; i < 8; ++i) {
-----------------------------------------------------------------------
Summary of changes:
libavcodec/vulkan/prores_idct.comp | 57 +++++++++++++++++++++++++-------------
1 file changed, 37 insertions(+), 20 deletions(-)
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