[PR] avcodec/vulkan_encode: speed up hevc_vulkan with encode optimizations (PR #24085)

PR #24085 opened by t-boiko
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24085
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24085.patch

Without ALLOW_ENCODE_PARAMETER_OPTIMIZATIONS and with min CU forced to
8x8, hevc_vulkan keeps a much heavier encode config at common quality
levels than h264_vulkan (16x16 macroblocks, no min-CU SPS field). Set
the session flag and use min CU 16x16 when CTB >= 32; also fix
max_transform_hierarchy_depth_inter assignment.

Reporter cmd (1080p testsrc2, quality 1, 1000 frames):
  before: hevc ~200–317 fps vs higher h264
  after:  hevc 289/325/358 fps, h264 288/317/359 fps (parity)


From 5de6c689204b272d85d0007c1f3ecde2703a3c03 Mon Sep 17 00:00:00 2001
From: Tymur Boiko <[email protected]>
Date: Tue, 11 Aug 2026 18:24:18 +0200
Subject: [PATCH] avcodec/vulkan_encode: speed up hevc_vulkan with encode
 optimizations
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Without ALLOW_ENCODE_PARAMETER_OPTIMIZATIONS and with min CU forced to
8x8, hevc_vulkan keeps a much heavier encode config at common quality
levels than h264_vulkan (16x16 macroblocks, no min-CU SPS field). Set
the session flag and use min CU 16x16 when CTB >= 32; also fix
max_transform_hierarchy_depth_inter assignment.

Reporter cmd (1080p testsrc2, quality 1, 1000 frames):
  before: hevc ~200–317 fps vs higher h264
  after:  hevc 289/325/358 fps, h264 288/317/359 fps (parity)
---
 libavcodec/vulkan_encode.c      |  4 +++-
 libavcodec/vulkan_encode_h265.c | 13 ++++++++++---
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/libavcodec/vulkan_encode.c b/libavcodec/vulkan_encode.c
index 3a2cf101f4..bc18be0d7f 100644
--- a/libavcodec/vulkan_encode.c
+++ b/libavcodec/vulkan_encode.c
@@ -1058,7 +1058,9 @@ av_cold int ff_vulkan_encode_init(AVCodecContext *avctx, FFVulkanEncodeContext *
 
     /* Create session */
     session_create.pVideoProfile = &ctx->profile;
-    session_create.flags = 0x0;
+    /* Allow the implementation to optimize codec parameters for the selected
+     * quality level (e.g. CU size). Matches typical encode-sample usage. */
+    session_create.flags = VK_VIDEO_SESSION_CREATE_ALLOW_ENCODE_PARAMETER_OPTIMIZATIONS_BIT_KHR;
     session_create.queueFamilyIndex = ctx->qf_enc->idx;
     session_create.maxCodedExtent = ctx->caps.maxCodedExtent;
     session_create.maxDpbSlots = ctx->caps.maxDpbSlots;
diff --git a/libavcodec/vulkan_encode_h265.c b/libavcodec/vulkan_encode_h265.c
index 7ed0fdbe77..942866a465 100644
--- a/libavcodec/vulkan_encode_h265.c
+++ b/libavcodec/vulkan_encode_h265.c
@@ -793,14 +793,21 @@ static av_cold int init_sequence_headers(AVCodecContext *avctx)
     else if (enc->caps.transformBlockSizes & VK_VIDEO_ENCODE_H265_TRANSFORM_BLOCK_SIZE_4_BIT_KHR)
         max_tb_size = 4;
 
-    units->raw_sps.log2_min_luma_coding_block_size_minus3 = 0;
-    units->raw_sps.log2_diff_max_min_luma_coding_block_size = av_log2(max_ctb_size) - 3;
+    /* Prefer 16x16 min CU when the CTB is at least 32; 8x8 min CU is much
+     * more expensive on some implementations for the common quality levels. */
+    if (max_ctb_size >= 32) {
+        units->raw_sps.log2_min_luma_coding_block_size_minus3 = 1;
+        units->raw_sps.log2_diff_max_min_luma_coding_block_size = av_log2(max_ctb_size) - 4;
+    } else {
+        units->raw_sps.log2_min_luma_coding_block_size_minus3 = 0;
+        units->raw_sps.log2_diff_max_min_luma_coding_block_size = av_log2(max_ctb_size) - 3;
+    }
     units->raw_sps.log2_min_luma_transform_block_size_minus2 = av_log2(min_tb_size) - 2;
     units->raw_sps.log2_diff_max_min_luma_transform_block_size = av_log2(max_tb_size) - av_log2(min_tb_size);
 
     max_transform_hierarchy = av_log2(max_ctb_size) - av_log2(min_tb_size);
     units->raw_sps.max_transform_hierarchy_depth_intra = max_transform_hierarchy;
-    units->raw_sps.max_transform_hierarchy_depth_intra = max_transform_hierarchy;
+    units->raw_sps.max_transform_hierarchy_depth_inter = max_transform_hierarchy;
 
     units->raw_sps.vui.bitstream_restriction_flag = 0;
     units->raw_sps.vui.max_bytes_per_pic_denom = 2;
-- 
2.52.0

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