demuxer: Fix demuxer assert logic and refactor FindFFmpeg by crmurillo · Pull Request #186 · KhronosGroup/Vulkan-Video-Samples

crmurillo · 2026-03-20T14:50:53Z

Description

This PR addresses two issues:

Logic inside the demuxer to detect errors in case FFmpeg is not found.

When FFmpeg is not found at build time and no codec is explicitly passed at runtime, codecType defaults to VK_VIDEO_CODEC_OPERATION_NONE_KHR. The assert() calls validating this are stripped in release builds, so the demuxer silently proceeds with invalid parameters and fails with a misleading "Video decode queue family not supported" error. See linked issue for more details.

The cmake logic to detect FFmpeg and the relevant required libraries.

The FindFFmpeg.cmake module had two separate search passes for FFmpeg libraries: one via a custom FFMPEG_FIND macro and another via pkg_check_modules + find_library. It used FFMPEG as the pkg-config prefix, which caused pkg-config to overwrite the module's own output variables

Type of change

bug fix

Issue (optional)

Fixes #185.

Tests

NVIDIA GeForce RTX 4060 Ti / NVIDIA 595.44.00 / Ubuntu 24.04.4 LTS

Total Tests: 73
Passed: 62
Crashed: 0
Failed: 0
Not Supported: 9
Skipped: 2 (in skip list)
Success Rate: 100.0%

AMD Radeon RX 7600 (RADV NAVI33) / radv Mesa 26.1.0-devel (git-055aec542e) / Ubuntu 24.04.4 LTS

Total Tests: 73
Passed: 63
Crashed: 0
Failed: 0
Not Supported: 6
Skipped: 4 (in skip list)
Success Rate: 100.0%

Intel(R) UHD Graphics 770 (ADL-S GT1) / Intel open-source Mesa driver Mesa 26.1.0-devel (git-055aec542e) / Ubuntu 24.04.4 LTS

Total Tests: 73
Passed: 54
Crashed: 0
Failed: 0
Not Supported: 14
Skipped: 5 (in skip list)
Success Rate: 100.0%

AMD Radeon RX 6600 / AMD proprietary driver 26.3.1 (AMD proprietary shader compiler) / Windows 10

Total Tests: 73
Passed: 37
Crashed: 0
Failed: 0
Not Supported: 28
Skipped: 8 (in skip list)
Success Rate: 100.0%

…ions The module searched for FFmpeg libraries twice (once via a macro, once via pkg-config + find_library) and used "FFMPEG" as the pkg-config prefix, which meant pkg-config wrote over the module's own output variables like FFMPEG_FOUND and FFMPEG_LIBRARIES. The following changes were made: - Replace with a single search pass using PC_FFMPEG as the pkg-config prefix. - Remove avdevice/x264/x265 since nothing links against them. - Drop the outdated Win32 stdint.h check. - Make swscale optional. - Split FFMPEG_INCLUDE_DIR into per-component include dirs and centralize search paths to eliminate duplication across find_library calls. - Move Windows FFmpeg discovery into FindFFmpeg. - Unify FFmpeg linking in demo and test targets to use FFMPEG_LIB* variables on all platforms.

When FFmpeg is not found and no codec is explicitly passed, codecType defaults to VK_VIDEO_CODEC_OPERATION_NONE_KHR). In release builds, the asserts validating this are stripped, causing the demuxer to silently proceed with invalid parameters and ultimately fail with a misleading "Video decode queue family not supported by hardware/driver" error. Replace asserts with explicit validation that returns VK_ERROR_FORMAT_NOT_SUPPORTED with descriptive error messages. Also print a hint when FFmpeg demuxer support is not available, since this is the most common cause of the failure.

Updated the list of skipped tests for the proprietary AMD driver (Windows).

No source file references swscale, therefore, the optional lookup was dead code. Drop it from the module.

dabrain34 · 2026-04-27T10:30:24Z

 find_package(PkgConfig QUIET)
 if(PKG_CONFIG_FOUND)
-    pkg_check_modules(FFMPEG QUIET
+    pkg_check_modules(PC_FFMPEG QUIET


the package config result should be high priority result setting all the necessary variable. I dont know if all the search and find are necessary afterwhile

dabrain34 · 2026-04-27T10:33:29Z

+)
+
+# Find required libraries
+find_library(FFMPEG_LIBAVCODEC_LIBRARIES


this is kind of confusing to have LIBARIES when we are searching for only one library. can we use FFMPEG_LIBAVCODEC_LIBRARY ?

dabrain34 · 2026-04-27T10:44:26Z

+# Windows FFmpeg paths
+if(WIN32)
+    set(FFMPEG_WIN32_PREBUILT_ROOT "${CMAKE_CURRENT_SOURCE_DIR}/vk_video_decoder/bin/libs/ffmpeg")
+    if((CMAKE_GENERATOR_PLATFORM MATCHES "^(aarch64|arm64|ARM64)"))


it seems that CMAKE_GENERATOR_PLATFORM is only used by visual studio generator so it might fail with ninja generation. Better to use CMAKE_SYSTEM_PROCESSOR, see

https://cmake.org/cmake/help/latest/variable/CMAKE_GENERATOR_PLATFORM.html

https://cmake.org/cmake/help/latest/variable/CMAKE_SYSTEM_PROCESSOR.html

There is unnecessary double parenthesis

dabrain34 · 2026-04-27T11:02:34Z

+    ${FFMPEG_ROOT}/include
+    ${FFMPEG_WIN32_PREBUILT_DIR}/include
+    ${PC_FFMPEG_INCLUDE_DIRS}
+    /Library/Frameworks


it seems that this path wont exist as it is and no binary will be found from here. Can you search in homebrew instead such as /opt/homebrew/

dabrain34 · 2026-04-27T11:05:13Z

+    message(STATUS "  libavcodec:  ${FFMPEG_LIBAVCODEC_LIBRARIES}")
+    message(STATUS "  libavformat: ${FFMPEG_LIBAVFORMAT_LIBRARIES}")
+    message(STATUS "  libavutil:   ${FFMPEG_LIBAVUTIL_LIBRARIES}")
+    include_directories(${FFMPEG_INCLUDE_DIRS})


this is project wide maybe better to have it at target level with:

target_include_directories

dabrain34 · 2026-04-27T11:06:17Z

 if(FFMPEG_FOUND)
-    message("Found FFMPEG/LibAV libraries")
-    include_directories(${FFMPEG_INCLUDE_DIR})
+    message(STATUS "  libavcodec:  ${FFMPEG_LIBAVCODEC_LIBRARIES}")


use FFMPEG_LIBAVCODEC_LIBRARy

dabrain34 · 2026-04-27T11:06:52Z

+    ${FFMPEG_WIN32_PREBUILT_DIR}/lib
+    ${PC_FFMPEG_LIBRARY_DIRS}
+    /Library/Frameworks
+    ~/Library/Frameworks


I dont think we gonna find any ffmpeg include dir here

crmurillo changed the title ~~Fix demuxer assert logic and refactor FindFFmpeg~~ demuxer: Fix demuxer assert logic and refactor FindFFmpeg Mar 20, 2026