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Reference the AVFrame while the backing DMA-BUFs are used for scanout

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This prevents tearing and other artifacts caused by the decoder
writing to a DMA-BUF that is currently being displayed.
This commit is contained in:
Cameron Gutman
2026-01-04 18:47:00 -06:00
parent de0fb72424
commit 34881599f5
2 changed files with 76 additions and 44 deletions
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9
app/streaming/video/ffmpeg-renderers/drm.cpp
View File

@@ -1158,7 +1158,7 @@ void DrmRenderer::notifyOverlayUpdated(Overlay::OverlayType type)
// Queue the plane flip with the new FB
//
// NB: This takes ownership of the FB and dumb buffer, even on failure
m_PropSetter.flipPlane(m_OverlayPlanes[type], fbId, dumbBuffer);
m_PropSetter.flipPlane(m_OverlayPlanes[type], fbId, dumbBuffer, nullptr);
SDL_FreeSurface(newSurface);
}
@@ -1410,7 +1410,12 @@ void DrmRenderer::renderFrame(AVFrame* frame)
// Update the video plane
//
// NB: This takes ownership of fbId, even on failure
m_PropSetter.flipPlane(m_VideoPlane, fbId, 0);
//
// NB2: We reference the AVFrame (which also references the AVBuffers backing the frame itself
// and the opaque_ref which may store our DRM-PRIME mapping) for frames backed by DMA-BUFs in
// order to keep those from being reused by the decoder while they're still being scanned out.
m_PropSetter.flipPlane(m_VideoPlane, fbId, 0,
(m_DrmPrimeBackend || frame->format == AV_PIX_FMT_DRM_PRIME) ? frame : nullptr);
// Apply pending atomic transaction (if in atomic mode)
m_PropSetter.apply();

111
app/streaming/video/ffmpeg-renderers/drm.h
View File

@@ -200,10 +200,12 @@ class DrmRenderer : public IFFmpegRenderer {
struct PlaneBuffer {
uint32_t fbId;
uint32_t dumbBufferHandle;
AVFrame* frame;
// Atomic only
uint32_t pendingFbId;
uint32_t pendingDumbBuffer;
AVFrame* pendingFrame;
bool modified;
};
@@ -293,9 +295,15 @@ class DrmRenderer : public IFFmpegRenderer {
}
// Unconditionally takes ownership of fbId and dumbBufferHandle (if present)
bool flipPlane(const DrmPropertyMap& plane, uint32_t fbId, uint32_t dumbBufferHandle) {
// If provided, frame is referenced to keep the FB's backing DMA-BUFs around
bool flipPlane(const DrmPropertyMap& plane, uint32_t fbId, uint32_t dumbBufferHandle, AVFrame* frame) {
bool ret;
// If a frame was provided, clone a reference to it to hold until the next flip
if (frame) {
frame = av_frame_clone(frame);
}
if (m_Atomic) {
std::lock_guard lg { m_Lock };
@@ -303,9 +311,11 @@ class DrmRenderer : public IFFmpegRenderer {
if (ret) {
// If we updated the FB_ID property, free the old pending buffer.
// Otherwise, we'll free the new buffer which was never used.
std::swap(fbId, m_PlaneBuffers[plane.objectId()].pendingFbId);
std::swap(dumbBufferHandle, m_PlaneBuffers[plane.objectId()].pendingDumbBuffer);
m_PlaneBuffers[plane.objectId()].modified = true;
auto &pb = m_PlaneBuffers[plane.objectId()];
std::swap(fbId, pb.pendingFbId);
std::swap(dumbBufferHandle, pb.pendingDumbBuffer);
std::swap(frame, pb.pendingFrame);
pb.modified = true;
}
}
else {
@@ -329,8 +339,10 @@ class DrmRenderer : public IFFmpegRenderer {
if (ret) {
std::lock_guard lg { m_Lock };
std::swap(fbId, m_PlaneBuffers[plane.objectId()].fbId);
std::swap(dumbBufferHandle, m_PlaneBuffers[plane.objectId()].dumbBufferHandle);
auto &pb = m_PlaneBuffers[plane.objectId()];
std::swap(fbId, pb.fbId);
std::swap(dumbBufferHandle, pb.dumbBufferHandle);
std::swap(frame, pb.frame);
}
else {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
@@ -348,6 +360,7 @@ class DrmRenderer : public IFFmpegRenderer {
destroyBuf.handle = dumbBufferHandle;
drmIoctl(m_Fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroyBuf);
}
av_frame_free(&frame);
return ret;
}
@@ -391,7 +404,7 @@ class DrmRenderer : public IFFmpegRenderer {
void disablePlane(const DrmPropertyMap& plane) {
if (plane.isValid()) {
configurePlane(plane, 0, 0, 0, 0, 0, 0, 0, 0, 0);
flipPlane(plane, 0, 0);
flipPlane(plane, 0, 0, nullptr);
}
}
@@ -418,46 +431,60 @@ class DrmRenderer : public IFFmpegRenderer {
// 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;
// If we flipped to a new buffer, free the old one
if (ret) {
std::lock_guard lg { m_Lock };
// Update the buffer state for any modified planes
for (auto it = pendingBuffers.begin(); it != pendingBuffers.end(); it++) {
if (it->second.modified) {
if (it->second.fbId) {
drmModeRmFB(m_Fd, it->second.fbId);
it->second.fbId = 0;
}
if (it->second.dumbBufferHandle) {
struct drm_mode_destroy_dumb destroyBuf = {};
destroyBuf.handle = it->second.dumbBufferHandle;
drmIoctl(m_Fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroyBuf);
it->second.dumbBufferHandle = 0;
}
// The pending buffers become the active buffers for this FB
m_PlaneBuffers[it->first].fbId = it->second.pendingFbId;
m_PlaneBuffers[it->first].dumbBufferHandle = it->second.pendingDumbBuffer;
}
else if (it->second.fbId || it->second.dumbBufferHandle) {
// This FB wasn't modified in this commit, so the current buffers stay around
m_PlaneBuffers[it->first].fbId = it->second.fbId;
m_PlaneBuffers[it->first].dumbBufferHandle = it->second.dumbBufferHandle;
}
// NB: We swapped in a new plane buffers map which will clear the modified value.
// It's important that we don't try to clear it here because we might stomp on
// a flipPlane() performed by another thread that queued up another modification.
}
}
else {
if (!ret) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
"drmModeAtomicCommit() failed: %d",
errno);
}
// Update the buffer state for any modified planes
std::lock_guard lg { m_Lock };
for (auto it = pendingBuffers.begin(); it != pendingBuffers.end(); it++) {
if (ret && it->second.modified) {
if (it->second.fbId) {
drmModeRmFB(m_Fd, it->second.fbId);
it->second.fbId = 0;
}
if (it->second.dumbBufferHandle) {
struct drm_mode_destroy_dumb destroyBuf = {};
destroyBuf.handle = it->second.dumbBufferHandle;
drmIoctl(m_Fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroyBuf);
it->second.dumbBufferHandle = 0;
}
av_frame_free(&it->second.frame);
// The pending buffers become the active buffers for this FB
auto &pb = m_PlaneBuffers[it->first];
pb.fbId = it->second.pendingFbId;
pb.dumbBufferHandle = it->second.pendingDumbBuffer;
pb.frame = it->second.pendingFrame;
}
else if (!ret || it->second.fbId || it->second.dumbBufferHandle || it->second.frame) {
// Free the old pending buffers on a failed commit
if (it->second.pendingFbId) {
SDL_assert(!ret);
drmModeRmFB(m_Fd, it->second.pendingFbId);
}
if (it->second.pendingDumbBuffer) {
SDL_assert(!ret);
struct drm_mode_destroy_dumb destroyBuf = {};
destroyBuf.handle = it->second.pendingDumbBuffer;
drmIoctl(m_Fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroyBuf);
}
av_frame_free(&it->second.pendingFrame);
// This FB wasn't modified in this commit, so the current buffers stay around
auto &pb = m_PlaneBuffers[it->first];
pb.fbId = it->second.fbId;
pb.dumbBufferHandle = it->second.dumbBufferHandle;
pb.frame = it->second.frame;
}
// NB: We swapped in a new plane buffers map which will clear the modified value.
// It's important that we don't try to clear it here because we might stomp on
// a flipPlane() performed by another thread that queued up another modification.
}
drmModeAtomicFree(req);
return ret;
}