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Slow video handling #1334

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Slow video handling#1334
@BlueriteSoul

Description

@BlueriteSoul
BlueriteSoul
opened on Oct 16, 2025
  1. The Core Issue

  • Problem: Video seeking (specifically backwards seeking using seekTo(target, true)) is extremely laggy/stuck in the webview_vanilla app, but works flawlessly when the identical index.html file is opened directly in Firefox.

  • Symptom Detail: When seeking back, the audio jumps correctly, but the video frame either remains stuck on the previous frame or only updates to a frame slightly before the last one. Forward seeking works as expected.

  • Reproducibility: 100% on this system. I tried to capture the problem on video (failed to capture sound): https://www.youtube.com/watch?v=FUeQI_P_kiM

  • Reason for opening an issue: Since it works as expected in Firefox, this seems to be a bug that is beyond my capability, so I'd like to help track it down.

  1. Software / Project Details

  • Jerry's Youtube Cutter: https://github.com/BlueriteSoul/jerrysYTcutter

  • Webview Library: webview/webview.h (Version/Commit Hash: 55b438d)

  • Backend Used: WebKitGTK 6.0 (as specified in build.sh)

  • Video Platform: YouTube IFrame API

  • Relevant JS Snippet (Seeking function):

player.seekTo(finalTarget, true); // The critical API call
// Followed by a 200ms timeout for frame update (SEEK_SETTLE_MS)
  1. System and Dependency Output

A. OS and Kernel:

uname -a; cat /etc/os-release
Linux archgram 6.17.2-arch1-1 #1 SMP PREEMPT_DYNAMIC Sun, 12 Oct 2025 12:45:18 +0000 x86_64 GNU/Linux
NAME="Arch Linux"
PRETTY_NAME="Arch Linux"
ID=arch
BUILD_ID=rolling
ANSI_COLOR="38;2;23;147;209"
HOME_URL="https://archlinux.org/"
DOCUMENTATION_URL="https://wiki.archlinux.org/"
SUPPORT_URL="https://bbs.archlinux.org/"
BUG_REPORT_URL="https://gitlab.archlinux.org/groups/archlinux/-/issues"
PRIVACY_POLICY_URL="https://terms.archlinux.org/docs/privacy-policy/"
LOGO=archlinux-logo

B. CPU and Graphics Drivers:

lscpu; lspci -k | grep -EA3 'VGA|3D|Display'
Architecture:                x86_64
  CPU op-mode(s):            32-bit, 64-bit
  Address sizes:             39 bits physical, 48 bits virtual
  Byte Order:                Little Endian
CPU(s):                      8
  On-line CPU(s) list:       0-7
Vendor ID:                   GenuineIntel
  Model name:                Intel(R) Core(TM) i7-1065G7 CPU @ 1.30GHz
    CPU family:              6
    Model:                   126
    Thread(s) per core:      2
    Core(s) per socket:      4
    Socket(s):               1
    Stepping:                5
    CPU(s) scaling MHz:      29%
    CPU max MHz:             3900.0000
    CPU min MHz:             400.0000
    BogoMIPS:                2995.20
    Flags:                   fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush d
                             ts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc 
                             art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf ts
                             c_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 
                             xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx
                              f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb ssbd ibrs ibpb stibp ibrs_
                             enhanced tpr_shadow flexpriority ept vpid ept_ad fsgsbase tsc_adjust sgx bmi1 avx
                             2 smep bmi2 erms invpcid avx512f avx512dq rdseed adx smap avx512ifma clflushopt i
                             ntel_pt avx512cd sha_ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves split_lo
                             ck_detect dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp hwp_pkg_r
                             eq vnmi avx512vbmi umip pku ospke avx512_vbmi2 gfni vaes vpclmulqdq avx512_vnni a
                             vx512_bitalg avx512_vpopcntdq rdpid sgx_lc fsrm md_clear flush_l1d arch_capabilit
                             ies
Virtualization features:     
  Virtualization:            VT-x
Caches (sum of all):         
  L1d:                       192 KiB (4 instances)
  L1i:                       128 KiB (4 instances)
  L2:                        2 MiB (4 instances)
  L3:                        8 MiB (1 instance)
NUMA:                        
  NUMA node(s):              1
  NUMA node0 CPU(s):         0-7
Vulnerabilities:             
  Gather data sampling:      Mitigation; Microcode
  Ghostwrite:                Not affected
  Indirect target selection: Mitigation; Aligned branch/return thunks
  Itlb multihit:             KVM: Mitigation: Split huge pages
  L1tf:                      Not affected
  Mds:                       Not affected
  Meltdown:                  Not affected
  Mmio stale data:           Mitigation; Clear CPU buffers; SMT vulnerable
  Old microcode:             Not affected
  Reg file data sampling:    Not affected
  Retbleed:                  Mitigation; Enhanced IBRS
  Spec rstack overflow:      Not affected
  Spec store bypass:         Mitigation; Speculative Store Bypass disabled via prctl
  Spectre v1:                Mitigation; usercopy/swapgs barriers and __user pointer sanitization
  Spectre v2:                Mitigation; Enhanced / Automatic IBRS; IBPB conditional; PBRSB-eIBRS SW sequence;
                              BHI SW loop, KVM SW loop
  Srbds:                     Mitigation; Microcode
  Tsa:                       Not affected
  Tsx async abort:           Not affected
  Vmscape:                   Not affected
00:02.0 VGA compatible controller: Intel Corporation Iris Plus Graphics G7 (rev 07)
        Subsystem: LG Electronics, Inc. Device 0361
        Kernel driver in use: i915
        Kernel modules: i915

C. WebkitGTK / GTK Versions:

pacman -Qs webkitgtk | grep -E 'webkitgtk|Version'
local/webkitgtk-6.0 2.50.1-1
pacman -Qs gtk4 | grep -E 'gtk4|Version'
local/gtk4 1:4.20.2-3
pkg-config --cflags --libs gtk4 webkitgtk-6.0
-I/usr/include/webkitgtk-6.0 -I/usr/include/gtk-4.0 -I/usr/include/pango-1.0 -I/usr/include/fribidi -I/usr/include/harfbuzz -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/glycin-2 -I/usr/include/cairo -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/pixman-1 -I/usr/include/graphene-1.0 -I/usr/lib/graphene-1.0/include -mfpmath=sse -msse -msse2 -I/usr/include/libsoup-3.0 -I/usr/include/libmount -I/usr/include/blkid -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/sysprof-6 -pthread -lwebkitgtk-6.0 -lgtk-4 -lpangocairo-1.0 -lpango-1.0 -lharfbuzz -lgdk_pixbuf-2.0 -lcairo-gobject -lcairo -lvulkan -lgraphene-1.0 -lsoup-3.0 -lgio-2.0 -lgmodule-2.0 -pthread -ljavascriptcoregtk-6.0 -lgobject-2.0 -lglib-2.0

D. X11 vs Wayland (The Windowing System)

echo $XDG_SESSION_TYPE
wayland

E. Graphics Backend for WebKitGTK

vainfo
Trying display: wayland
vainfo: VA-API version: 1.22 (libva 2.22.0)
vainfo: Driver version: Intel iHD driver for Intel(R) Gen Graphics - 25.3.4 ()
vainfo: Supported profile and entrypoints
      VAProfileNone                   : VAEntrypointVideoProc
      VAProfileNone                   : VAEntrypointStats
      VAProfileMPEG2Simple            : VAEntrypointVLD
      VAProfileMPEG2Simple            : VAEntrypointEncSlice
      VAProfileMPEG2Main              : VAEntrypointVLD
      VAProfileMPEG2Main              : VAEntrypointEncSlice
      VAProfileH264Main               : VAEntrypointVLD
      VAProfileH264Main               : VAEntrypointEncSlice
      VAProfileH264Main               : VAEntrypointFEI
      VAProfileH264Main               : VAEntrypointEncSliceLP
      VAProfileH264High               : VAEntrypointVLD
      VAProfileH264High               : VAEntrypointEncSlice
      VAProfileH264High               : VAEntrypointFEI
      VAProfileH264High               : VAEntrypointEncSliceLP
      VAProfileVC1Simple              : VAEntrypointVLD
      VAProfileVC1Main                : VAEntrypointVLD
      VAProfileVC1Advanced            : VAEntrypointVLD
      VAProfileJPEGBaseline           : VAEntrypointVLD
      VAProfileJPEGBaseline           : VAEntrypointEncPicture
      VAProfileH264ConstrainedBaseline: VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointEncSlice
      VAProfileH264ConstrainedBaseline: VAEntrypointFEI
      VAProfileH264ConstrainedBaseline: VAEntrypointEncSliceLP
      VAProfileVP8Version0_3          : VAEntrypointVLD
      VAProfileVP8Version0_3          : VAEntrypointEncSlice
      VAProfileHEVCMain               : VAEntrypointVLD
      VAProfileHEVCMain               : VAEntrypointEncSlice
      VAProfileHEVCMain               : VAEntrypointFEI
      VAProfileHEVCMain               : VAEntrypointEncSliceLP
      VAProfileHEVCMain10             : VAEntrypointVLD
      VAProfileHEVCMain10             : VAEntrypointEncSlice
      VAProfileHEVCMain10             : VAEntrypointEncSliceLP
      VAProfileVP9Profile0            : VAEntrypointVLD
      VAProfileVP9Profile1            : VAEntrypointVLD
      VAProfileVP9Profile2            : VAEntrypointVLD
      VAProfileVP9Profile3            : VAEntrypointVLD
      VAProfileHEVCMain422_10         : VAEntrypointVLD
      VAProfileHEVCMain422_10         : VAEntrypointEncSlice
      VAProfileHEVCMain444            : VAEntrypointVLD
      VAProfileHEVCMain444            : VAEntrypointEncSliceLP
      VAProfileHEVCMain444_10         : VAEntrypointVLD
      VAProfileHEVCMain444_10         : VAEntrypointEncSliceLP

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