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Dynamically adjust libplacebo swapchain depth on macOS

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Direct-to-display mode on some Macs (M4 Mac Mini) can retain our drawables, which cuts the frame rate in half if we're in double-buffered mode.

We don't want to use triple-buffered mode all the time because it increases latency when used if not required, so detect delayed presentation and enable it on the fly if needed.
This commit is contained in:
Cameron Gutman
2026-06-23 21:09:20 -05:00
parent 06bd8a730b
commit d997a0d0c8
2 changed files with 83 additions and 24 deletions
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app/streaming/video/ffmpeg-renderers/plvk.cpp
+68 -24
View File
@@ -421,6 +421,7 @@ bool PlVkRenderer::isExtensionSupportedByPhysicalDevice(VkPhysicalDevice device,
bool PlVkRenderer::initialize(PDECODER_PARAMETERS params)
{
m_Window = params->window;
m_MaxVideoFps = params->frameRate;
unsigned int instanceExtensionCount = 0;
if (!SDL_Vulkan_GetInstanceExtensions(params->window, &instanceExtensionCount, nullptr)) {
@@ -488,18 +489,17 @@ bool PlVkRenderer::initialize(PDECODER_PARAMETERS params)
return false;
}
VkPresentModeKHR presentMode;
if (params->enableVsync) {
// FIFO mode improves frame pacing compared with Mailbox, especially for
// platforms like X11 that lack a VSyncSource implementation for Pacer.
presentMode = VK_PRESENT_MODE_FIFO_KHR;
m_VkPresentMode = VK_PRESENT_MODE_FIFO_KHR;
}
else {
// We want immediate mode for V-Sync disabled if possible
if (isPresentModeSupportedByPhysicalDevice(m_Vulkan->phys_device, VK_PRESENT_MODE_IMMEDIATE_KHR)) {
SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
"Using Immediate present mode with V-Sync disabled");
presentMode = VK_PRESENT_MODE_IMMEDIATE_KHR;
m_VkPresentMode = VK_PRESENT_MODE_IMMEDIATE_KHR;
}
else {
SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
@@ -509,41 +509,26 @@ bool PlVkRenderer::initialize(PDECODER_PARAMETERS params)
if (isPresentModeSupportedByPhysicalDevice(m_Vulkan->phys_device, VK_PRESENT_MODE_FIFO_RELAXED_KHR)) {
SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
"Using FIFO Relaxed present mode with V-Sync disabled");
presentMode = VK_PRESENT_MODE_FIFO_RELAXED_KHR;
m_VkPresentMode = VK_PRESENT_MODE_FIFO_RELAXED_KHR;
}
// Mailbox at least provides non-blocking behavior
else if (isPresentModeSupportedByPhysicalDevice(m_Vulkan->phys_device, VK_PRESENT_MODE_MAILBOX_KHR)) {
SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
"Using Mailbox present mode with V-Sync disabled");
presentMode = VK_PRESENT_MODE_MAILBOX_KHR;
m_VkPresentMode = VK_PRESENT_MODE_MAILBOX_KHR;
}
// FIFO is always supported
else {
SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
"Using FIFO present mode with V-Sync disabled");
presentMode = VK_PRESENT_MODE_FIFO_KHR;
m_VkPresentMode = VK_PRESENT_MODE_FIFO_KHR;
}
}
}
pl_vulkan_swapchain_params vkSwapchainParams = {};
vkSwapchainParams.surface = m_VkSurface;
vkSwapchainParams.present_mode = presentMode;
vkSwapchainParams.swapchain_depth = 1; // No queued frames
#if PL_API_VER >= 338
vkSwapchainParams.disable_10bit_sdr = true; // Some drivers don't dither 10-bit SDR output correctly
#endif
{
// Don't let Qt take DRM master from us during pl_vulkan_create_swapchain()
DrmMasterLocker locker;
m_Swapchain = pl_vulkan_create_swapchain(m_Vulkan, &vkSwapchainParams);
if (m_Swapchain == nullptr) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
"pl_vulkan_create_swapchain() failed");
return false;
}
// Start with a swapchain that is double-buffered for lowest display latency
if (!createSwapchain(1)) {
return false;
}
m_Renderer = pl_renderer_create(m_Log, m_Vulkan->gpu);
@@ -622,6 +607,35 @@ bool PlVkRenderer::initialize(PDECODER_PARAMETERS params)
return true;
}
bool PlVkRenderer::createSwapchain(int depth)
{
pl_swapchain_destroy(&m_Swapchain);
pl_vulkan_swapchain_params vkSwapchainParams = {};
vkSwapchainParams.surface = m_VkSurface;
vkSwapchainParams.present_mode = m_VkPresentMode;
vkSwapchainParams.swapchain_depth = depth;
#if PL_API_VER >= 338
vkSwapchainParams.disable_10bit_sdr = true; // Some drivers don't dither 10-bit SDR output correctly
#endif
{
// Don't let Qt take DRM master from us during pl_vulkan_create_swapchain()
DrmMasterLocker locker;
m_Swapchain = pl_vulkan_create_swapchain(m_Vulkan, &vkSwapchainParams);
if (m_Swapchain == nullptr) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
"pl_vulkan_create_swapchain() failed");
return false;
}
}
m_SwapchainDepth = depth;
return true;
}
bool PlVkRenderer::prepareDecoderContext(AVCodecContext *context, AVDictionary **)
{
if (m_HwDeviceCtx) {
@@ -991,6 +1005,10 @@ void PlVkRenderer::renderFrame(AVFrame *frame)
targetFrame.crop.x1 = dst.x + dst.w;
targetFrame.crop.y1 = dst.y + dst.h;
#ifdef PLVK_USE_DYNAMIC_SWAPCHAIN_DEPTH
Uint32 renderStartTime = SDL_GetTicks();
#endif
// Render the video image and overlays into the swapchain buffer
targetFrame.num_overlays = (int)overlays.size();
targetFrame.overlays = overlays.data();
@@ -1013,6 +1031,32 @@ void PlVkRenderer::renderFrame(AVFrame *frame)
goto UnmapExit;
}
#ifdef PLVK_USE_DYNAMIC_SWAPCHAIN_DEPTH
// Trigger a switch to triple-buffered mode if our frame presentation time
// exceeds 110% of the frame interval for half a second of frames.
if (SDL_GetTicks() - renderStartTime > (1100U / m_MaxVideoFps)) {
m_DelayedPresents++;
}
else if (m_DelayedPresents > 0) {
m_DelayedPresents--;
}
if (m_DelayedPresents == m_MaxVideoFps / 2 && m_SwapchainDepth < 2) {
SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
"Switching to triple-buffered swapchain after delayed presentations");
if (!createSwapchain(2)) {
// Recreate the renderer
SDL_Event event;
event.type = SDL_RENDER_DEVICE_RESET;
SDL_PushEvent(&event);
goto UnmapExit;
}
// Restore the swapchain's colorspace from the previous swapchain frame
pl_swapchain_colorspace_hint(m_Swapchain, &targetFrame.color);
}
#endif
#ifdef Q_OS_WIN32
// On Windows, we swap buffers here instead of waitToRender()
// to avoid some performance problems on Nvidia GPUs.
app/streaming/video/ffmpeg-renderers/plvk.h
+15
View File
@@ -23,6 +23,11 @@ private:
pl_vulkan m_Vulkan;
/* CVMetalTextureCacheRef */ void* m_TextureCache = nullptr;
};
// Work around direct-to-display mode sometimes (but not always!) blocking us
// from getting a new drawable while the current one is getting scanned out.
#define PLVK_USE_DYNAMIC_SWAPCHAIN_DEPTH 1
#endif
class PlVkRenderer : public IFFmpegRenderer {
@@ -49,6 +54,7 @@ private:
static void unlockQueue(AVHWDeviceContext *dev_ctx, uint32_t queue_family, uint32_t index);
static void overlayUploadComplete(void* opaque);
bool createSwapchain(int depth);
bool mapAvFrameToPlacebo(const AVFrame *frame, pl_frame* mappedFrame);
void unmapAvFrameFromPlacebo(const AVFrame *frame, pl_frame* mappedFrame);
bool populateQueues(int videoFormat);
@@ -68,13 +74,22 @@ private:
std::unique_ptr<MetalVulkanTextureFactory> m_MetalTextureFactory;
#endif
#ifdef PLVK_USE_DYNAMIC_SWAPCHAIN_DEPTH
int m_DelayedPresents = 0;
#endif
// SDL state
SDL_Window* m_Window = nullptr;
// Stream state
int m_MaxVideoFps;
// The libplacebo rendering state
pl_log m_Log = nullptr;
pl_vk_inst m_PlVkInstance = nullptr;
VkSurfaceKHR m_VkSurface = VK_NULL_HANDLE;
int m_SwapchainDepth = 0;
VkPresentModeKHR m_VkPresentMode;
pl_vulkan m_Vulkan = nullptr;
pl_swapchain m_Swapchain = nullptr;
pl_renderer m_Renderer = nullptr;