From 46d6799916128c17577d10193baa79e717f701b3 Mon Sep 17 00:00:00 2001
From: neatnoise <neatnoise@gmail.com>
Date: Sun, 19 Apr 2026 17:59:12 +0200
Subject: [PATCH] fix(linux/vulkan): change default rate control from VBR to
 CBR

VBR causes bitrate overshoots on complex frames, leading to network
congestion and frame drops during streaming. CBR provides more
consistent bitrate and better streaming experience.

Update default in config, web UI, and documentation.
---
 docs/configuration.md                                     | 4 ++--
 src/config.cpp                                            | 2 +-
 src_assets/common/assets/web/config.html                  | 2 +-
 src_assets/common/assets/web/public/assets/locale/en.json | 4 ++--
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/docs/configuration.md b/docs/configuration.md
index ec4e56dde9f..8e59c0ab0ad 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -3029,13 +3029,13 @@ editing the `conf` file in a text editor. Use the examples as reference.
     <tr>
         <td>Default</td>
         <td colspan="2">@code{}
-            4
+            2
             @endcode</td>
     </tr>
     <tr>
         <td>Example</td>
         <td colspan="2">@code{}
-            vk_rc_mode = 2
+            vk_rc_mode = 4
             @endcode</td>
     </tr>
     <tr>
diff --git a/src/config.cpp b/src/config.cpp
index 9faac6f93ab..a79f7d88151 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -503,7 +503,7 @@ namespace config {
 
     {
       2,  // vk.tune (default: ll - low latency)
-      4,  // vk.rc_mode (default: vbr)
+      2,  // vk.rc_mode (default: cbr)
     },
 
     {},  // capture
diff --git a/src_assets/common/assets/web/config.html b/src_assets/common/assets/web/config.html
index 979b0ac7055..513932a2cf9 100644
--- a/src_assets/common/assets/web/config.html
+++ b/src_assets/common/assets/web/config.html
@@ -338,7 +338,7 @@ <h1 class="my-4">{{ $t('config.configuration') }}</h1>
             name: "Vulkan Encoder",
             options: {
               "vk_tune": 2,
-              "vk_rc_mode": 4,
+              "vk_rc_mode": 2,
             },
           },
           {
diff --git a/src_assets/common/assets/web/public/assets/locale/en.json b/src_assets/common/assets/web/public/assets/locale/en.json
index 9d32b7357bc..30289b1eebc 100644
--- a/src_assets/common/assets/web/public/assets/locale/en.json
+++ b/src_assets/common/assets/web/public/assets/locale/en.json
@@ -381,11 +381,11 @@
     "upnp_desc": "Automatically configure port forwarding for streaming over the Internet",
     "vaapi_strict_rc_buffer": "Strictly enforce frame bitrate limits for H.264/HEVC on AMD GPUs",
     "vaapi_strict_rc_buffer_desc": "Enabling this option can avoid dropped frames over the network during scene changes, but video quality may be reduced during motion.",
-    "vk_rc_cbr": "CBR (Constant Bitrate)",
+    "vk_rc_cbr": "CBR (Constant Bitrate) (default)",
     "vk_rc_cqp": "CQP (Constant QP)",
     "vk_rc_mode": "Rate Control",
     "vk_rc_mode_desc": "Rate control mode for encoding. Auto lets the driver decide.",
-    "vk_rc_vbr": "VBR (Variable Bitrate) (default)",
+    "vk_rc_vbr": "VBR (Variable Bitrate)",
     "vk_tune": "Tuning",
     "vk_tune_desc": "Low latency modes reduce encoding delay at the cost of quality.",
     "vk_tune_hq": "High Quality (hq)",