PR #21042 opened by russelltg URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21042 Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21042.patch
When a frame is exported to DRM, it may be written to to read to in an asyncronous fashion. Make sure, on unmap of a Vulkan frame that was mapped to DRM, to import any fences that were put on the dmabuf. The context for myself here is I'm working on a vulkan-video based screen recorder, which allocates vulkan frames using ffmpeg, then exports them as DRM dmabuf to send to the compositor, which then writes to it. Without this change, I see all sorts of frame corruption because the read from ffmpeg's vulkan filter happens before/during the compositor writing to it. >From 52c81b688fcc77f6274c64911c67ace14cb7f4ec Mon Sep 17 00:00:00 2001 From: Russell Greene <[email protected]> Date: Fri, 28 Nov 2025 23:04:57 -0700 Subject: [PATCH] hwcontext_vulkan: add support for implict DRM sync for export When a frame is exported to DRM, it may be written to to read to in an asyncronous fashion. Make sure, on unmap of a Vulkan frame that was mapped to DRM, to import any fences that were put on the dmabuf --- libavutil/hwcontext_vulkan.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/libavutil/hwcontext_vulkan.c b/libavutil/hwcontext_vulkan.c index a2caaa0959..5b0607089c 100644 --- a/libavutil/hwcontext_vulkan.c +++ b/libavutil/hwcontext_vulkan.c @@ -3488,7 +3488,7 @@ fail: } static int vulkan_map_from_drm_frame_sync(AVHWFramesContext *hwfc, AVFrame *dst, - const AVFrame *src, int flags) + const AVDRMFrameDescriptor *desc, int flags) { int err; VkResult ret; @@ -3498,8 +3498,6 @@ static int vulkan_map_from_drm_frame_sync(AVHWFramesContext *hwfc, AVFrame *dst, AVVulkanDeviceContext *hwctx = &p->p; FFVulkanFunctions *vk = &p->vkctx.vkfn; - const AVDRMFrameDescriptor *desc = (AVDRMFrameDescriptor *)src->data[0]; - #ifdef DMA_BUF_IOCTL_EXPORT_SYNC_FILE if (p->vkctx.extensions & FF_VK_EXT_EXTERNAL_FD_SEM) { VkCommandBuffer cmd_buf; @@ -3619,6 +3617,7 @@ static int vulkan_map_from_drm(AVHWFramesContext *hwfc, AVFrame *dst, { int err = 0; AVVkFrame *f; + const AVDRMFrameDescriptor *desc = (AVDRMFrameDescriptor *)src->data[0]; if ((err = vulkan_map_from_drm_frame_desc(hwfc, &f, src, flags))) return err; @@ -3633,7 +3632,7 @@ static int vulkan_map_from_drm(AVHWFramesContext *hwfc, AVFrame *dst, if (err < 0) goto fail; - err = vulkan_map_from_drm_frame_sync(hwfc, dst, src, flags); + err = vulkan_map_from_drm_frame_sync(hwfc, dst, desc, flags); if (err < 0) return err; @@ -4037,6 +4036,10 @@ static void vulkan_unmap_to_drm(AVHWFramesContext *hwfc, HWMapDescriptor *hwmap) { AVDRMFrameDescriptor *drm_desc = hwmap->priv; + /* on unmap from DRM, make sure to import sync objects so that we are sync'd with any work that was + * done on the buffer while exported. We don't know if who used the dmabuf did reads or writes, so protect against both */ + vulkan_map_from_drm_frame_sync(hwfc, hwmap->source, drm_desc, AV_HWFRAME_MAP_READ | AV_HWFRAME_MAP_WRITE); + for (int i = 0; i < drm_desc->nb_objects; i++) close(drm_desc->objects[i].fd); -- 2.49.1 _______________________________________________ ffmpeg-devel mailing list -- [email protected] To unsubscribe send an email to [email protected]
