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Bring back atomic async page flip support

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Now that we're referencing the AVFrame to keep the buffers from
being reused during scanout, this should hopefully work better.
This commit is contained in:
Cameron Gutman 2026-01-04 19:34:13 -06:00
commit 8726c1c7d0
2 changed files with 37 additions and 4 deletions
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2
app/streaming/video/ffmpeg-renderers/drm.cpp
View file

@ -494,7 +494,7 @@ bool DrmRenderer::initialize(PDECODER_PARAMETERS params)
atomic = true;
}
m_PropSetter.initialize(m_DrmFd, atomic);
m_PropSetter.initialize(m_DrmFd, atomic, !params->enableVsync);
drmModePlaneRes* planeRes = drmModeGetPlaneResources(m_DrmFd);
if (planeRes == nullptr) {

39
app/streaming/video/ffmpeg-renderers/drm.h
View file

@ -14,6 +14,11 @@
#include <unordered_map>
#include <mutex>
// This is only defined in Linux 6.8+ headers
#ifndef DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP
#define DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP 0x15
#endif
// Newer libdrm headers have these HDR structs, but some older ones don't.
namespace DrmDefs
{
@ -234,9 +239,26 @@ class DrmRenderer : public IFFmpegRenderer {
DrmPropertySetter(const DrmPropertySetter &) = delete;
DrmPropertySetter(DrmPropertySetter &&) = delete;
void initialize(int drmFd, bool wantsAtomic) {
void initialize(int drmFd, bool wantsAtomic, bool wantsAsyncFlip) {
m_Fd = drmFd;
m_Atomic = wantsAtomic && drmSetClientCap(drmFd, DRM_CLIENT_CAP_ATOMIC, 1) == 0;
if (wantsAsyncFlip) {
uint64_t val;
if (!m_Atomic) {
SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
"V-sync cannot be disabled due to lack of atomic support");
}
else if (drmGetCap(m_Fd, DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP, &val) < 0 || !val) {
SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
"V-sync cannot be disabled due to lack of atomic async page flip support");
}
else {
SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
"Using atomic async page flips with V-sync disabled");
m_AsyncFlip = true;
}
}
}
bool set(const DrmProperty& prop, uint64_t value, bool verbose = true) {
@ -429,8 +451,18 @@ class DrmRenderer : public IFFmpegRenderer {
return true;
}
// We pass DRM_MODE_ATOMIC_ALLOW_MODESET because changing HDR state may require a modeset
bool ret = drmModeAtomicCommit(m_Fd, req, DRM_MODE_ATOMIC_ALLOW_MODESET, nullptr) == 0;
// Try an async flip if requested
bool ret = drmModeAtomicCommit(m_Fd, m_AtomicReq,
m_AsyncFlip ? DRM_MODE_PAGE_FLIP_ASYNC : DRM_MODE_ATOMIC_ALLOW_MODESET,
nullptr) == 0;
// The driver may not support async flips (especially if we changed a non-FB_ID property),
// so try again with a regular flip if we get an error from the async flip attempt.
//
// We pass DRM_MODE_ATOMIC_ALLOW_MODESET because changing HDR state may require a modeset.
if (!ret && m_AsyncFlip) {
ret = drmModeAtomicCommit(m_Fd, m_AtomicReq, DRM_MODE_ATOMIC_ALLOW_MODESET, this) == 0;
}
if (!ret) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
"drmModeAtomicCommit() failed: %d",
@ -496,6 +528,7 @@ class DrmRenderer : public IFFmpegRenderer {
private:
int m_Fd = -1;
bool m_Atomic = false;
bool m_AsyncFlip = false;
std::recursive_mutex m_Lock;
std::unordered_map<uint32_t, PlaneBuffer> m_PlaneBuffers;