518008 2026-03-22 18:42:13 +0000 Spectacle/KPipeWire on hybrid AMD+NVIDIA systems can select the wrong recording device, crashing MP4/H.264 and producing invalid WebM/VP9 files 2026-06-15 22:06:50 +0000 1 1 3 Frameworks and Libraries KPipeWire general 6.6.3 NixOS Linux RESOLVED FIXED NOR crash --- 1 marshland3943 plasma-bugs-null aleixpol nate Sevenseraphim https://invent.kde.org/plasma/kpipewire/-/commit/76f05c8ccfb6586d068d0f57c3b6554658865e54 6.7.0 0 oldest_to_newest 2505414 0 marshland3943 2026-03-22 18:42:13 +0000 SUMMARY On my hybrid AMD+NVIDIA laptop, Spectacle/KPipeWire recording on Wayland could choose the wrong GPU/render device for the recording pipeline. Before a local fix, KPipeWire selected AMD VAAPI on /dev/dri/renderD129 even though the active session/compositor was on NVIDIA. In that state: - MP4/H.264 recording crashed Spectacle - WebM/VP9 recording produced an invalid/corrupt file This appears to be caused by KPipeWire inferring GPU/render devices independently in multiple places instead of resolving the current session render node once and using it consistently. STEPS TO REPRODUCE 1. Use a hybrid AMD+NVIDIA laptop on Plasma Wayland, where the compositor/session is running on the NVIDIA dGPU and multiple render nodes exist. 2. Start a screen recording in Spectacle. 3. Record with MP4/H.264 or WebM/VP9 and stop the recording. OBSERVED RESULT KPipeWire selected AMD VAAPI for recording on this hybrid system: kpipewire_vaapi_logging: VAAPI: Mesa Gallium driver 26.0.2 for AMD Radeon Graphics (radeonsi, renoir, ACO, DRM 3.64, 6.19.8) in use for device "/dev/dri/renderD129" With MP4/H.264, Spectacle crashed. Relevant stack frames: Program terminated with signal SIGSEGV, Segmentation fault. #4 ff_hw_base_encode_receive_packet #6 avcodec_send_frame #7 Encoder::finish() from libKPipeWireRecord.so.6 #8 PipeWireProduce::stateChanged(pw_stream_state) from libKPipeWireRecord.so.6 With WebM/VP9, the output file was invalid/corrupt. Relevant errors: [matroska,webm @ ...] Duplicate element [matroska,webm @ ...] 0x00 at pos 100 (0x64) invalid as first byte of an EBML number [matroska,webm @ ...] Duplicate element [matroska,webm @ ...] 0x00 at pos 167 (0xa7) invalid as first byte of an EBML number [matroska,webm @ ...] Element at 0x5d ending at 0x1aec0100000066 exceeds containing master element ending at 0x1409 qt.multimedia.ffmpeg.mediadataholder: Could not open media. FFmpeg error description: End of file EXPECTED RESULT KPipeWire should resolve the current session render node once and use that same GPU consistently for: - VAAPI device selection - DMA-BUF import - stream modifier negotiation Recording should not crash for MP4/H.264 and should not produce invalid WebM/VP9 files. SOFTWARE/OS VERSIONS Operating System: NixOS Unstable channel KDE Plasma Version: 6.6.3 KDE Frameworks Version: 6.24.0 Qt Version: 6.10.2 Kernel Version: 6.19.8 (64-bit) Graphics Platform: Wayland Processors: 12 × AMD Ryzen 5 4600H with Radeon Graphics Memory: 40 GiB of RAM (38.6 GiB usable) Graphics Processor 1: NVIDIA GeForce GTX 1650 Graphics Processor 2: AMD Radeon Graphics ADDITIONAL INFORMATION I tested a local fix that introduces a shared session render-node resolver and uses it consistently across: - vaapiutils.cpp - dmabufhandler.cpp - pipewiresourcestream.cpp With that patch: - the recording pipeline uses the session render node instead of a foreign GPU - MP4/H.264 no longer crashes - WebM/VP9 produces a valid file The patch will be in the MR 2505421 1 bug-janitor 2026-03-22 19:16:28 +0000 A possibly relevant merge request was started @ https://invent.kde.org/plasma/kpipewire/-/merge_requests/239 2506318 2 nate 2026-03-26 17:23:18 +0000 Git commit 76f05c8ccfb6586d068d0f57c3b6554658865e54 by Nate Graham, on behalf of Marsh Land. Committed on 26/03/2026 at 17:23. Pushed by ngraham into branch 'master'. recording: Use the current session render node consistently across recording KPipeWire currently chooses GPU/render devices in multiple places independently (VAAPI selection, DMA-BUF handling, modifier negotiation). On hybrid systems this can lead to inconsistent GPU selection across the recording pipeline. This change introduces a shared session render-node resolver and uses the current session render node consistently for: - VAAPI device selection - DMA-BUF import path - stream modifier negotiation FIXED-IN: 6.7.0 M +2 -0 autotests/CMakeLists.txt M +2 -1 src/CMakeLists.txt M +8 -36 src/dmabufhandler.cpp M +16 -4 src/pipewiresourcestream.cpp A +92 -0 src/rendernodecontext.cpp * A +28 -0 src/rendernodecontext_p.h * M +17 -28 src/vaapiutils.cpp The files marked with a * at the end have a non valid license. Please read: https://community.kde.org/Policies/Licensing_Policy and use the headers which are listed at that page. https://invent.kde.org/plasma/kpipewire/-/commit/76f05c8ccfb6586d068d0f57c3b6554658865e54 2523319 3 kdedev 2026-06-15 22:06:50 +0000 *** Bug 519941 has been marked as a duplicate of this bug. ***