[FFmpeg-devel] [PATCH] hwcontext_vulkan: fix exporting multi-plane DRM modifiers

[Russell Greene <russellgreene8@gmail.com>]

From: Russell Greene <russell@shotover.com>

Previously, it was assumed that `drmFormatModifierPlaneCount` was one
for all modifiers when exporting, which is not always the case, in
particular for AMD GPUs and maybe others.

Fetch the number of memory planes and fill the structs appropriately in this situation.

The encoded stream is still bad in the case whre modifers are involved,
but I think this patch still stands on its own and I suspect that may be a driver bug.

A potential improvement that could be make is to cache the format
information, so we can avoid the two GetPhysicalDeviceFormatProperties2
calls for each export, as well as the allocation. I doubt this is very
expensive, but seemed worth noting.

Signed-off-by: Russell Greene <russellgreene8@gmail.com>
---
 libavutil/hwcontext_vulkan.c | 76 +++++++++++++++++++++++++++++++-----
 1 file changed, 67 insertions(+), 9 deletions(-)

diff --git a/libavutil/hwcontext_vulkan.c b/libavutil/hwcontext_vulkan.c
index ade0235ef1..d14fa4655b 100644
--- a/libavutil/hwcontext_vulkan.c
+++ b/libavutil/hwcontext_vulkan.c
@@ -3787,6 +3787,17 @@ static inline uint32_t vulkan_fmt_to_drm(VkFormat vkfmt)
     return DRM_FORMAT_INVALID;
 }
 
+#define MAX_MEMORY_PLANES 4
+static VkImageAspectFlags plane_index_to_aspect(int plane) {
+    if (plane == 0) return VK_IMAGE_ASPECT_MEMORY_PLANE_0_BIT_EXT;
+    if (plane == 1) return VK_IMAGE_ASPECT_MEMORY_PLANE_1_BIT_EXT;
+    if (plane == 2) return VK_IMAGE_ASPECT_MEMORY_PLANE_2_BIT_EXT;
+    if (plane == 3) return VK_IMAGE_ASPECT_MEMORY_PLANE_3_BIT_EXT;
+
+    av_assert2 (false && "Invalid plane index");
+    return VK_IMAGE_ASPECT_MEMORY_PLANE_0_BIT_EXT;
+}
+
 static int vulkan_map_to_drm(AVHWFramesContext *hwfc, AVFrame *dst,
                              const AVFrame *src, int flags)
 {
@@ -3855,14 +3866,65 @@ static int vulkan_map_to_drm(AVHWFramesContext *hwfc, AVFrame *dst,
 
     drm_desc->nb_layers = planes;
     for (int i = 0; i < drm_desc->nb_layers; i++) {
-        VkSubresourceLayout layout;
-        VkImageSubresource sub = {
-            .aspectMask = VK_IMAGE_ASPECT_MEMORY_PLANE_0_BIT_EXT,
+        VkDrmFormatModifierPropertiesListEXT modp = {
+            .sType = VK_STRUCTURE_TYPE_DRM_FORMAT_MODIFIER_PROPERTIES_LIST_EXT,
+        };
+        VkFormatProperties2 fmtp = {
+            .sType = VK_STRUCTURE_TYPE_FORMAT_PROPERTIES_2,
+            .pNext = &modp,
         };
         VkFormat plane_vkfmt = av_vkfmt_from_pixfmt(hwfc->sw_format)[i];
 
-        drm_desc->layers[i].format    = vulkan_fmt_to_drm(plane_vkfmt);
-        drm_desc->layers[i].nb_planes = 1;
+        drm_desc->layers[i].format = vulkan_fmt_to_drm(plane_vkfmt);
+
+        /* query drmFormatModifierCount by keeping pDrmFormatModifierProperties NULL */
+        vk->GetPhysicalDeviceFormatProperties2(hwctx->phys_dev, plane_vkfmt, &fmtp);
+
+        modp.pDrmFormatModifierProperties =
+            av_calloc(modp.drmFormatModifierCount, sizeof(*modp.pDrmFormatModifierProperties));
+        if (!modp.pDrmFormatModifierProperties) {
+            err = AVERROR(ENOMEM);
+            goto end;
+        }
+        vk->GetPhysicalDeviceFormatProperties2(hwctx->phys_dev, plane_vkfmt, &fmtp);
+
+        VkDrmFormatModifierPropertiesEXT *mod_props = NULL;
+        for (uint32_t i = 0; i < modp.drmFormatModifierCount; ++i) {
+            VkDrmFormatModifierPropertiesEXT *m = &modp.pDrmFormatModifierProperties[i];
+            if (m->drmFormatModifier == drm_mod.drmFormatModifier) {
+                mod_props = m;
+                break;
+            }
+        }
+
+        if (!mod_props) {
+            av_free(modp.pDrmFormatModifierProperties);
+            av_log(hwfc, AV_LOG_ERROR, "Cannot fetch modifier properties for modifier "PRIu64"!\n",
+                   drm_mod.drmFormatModifier);
+            err = AVERROR_EXTERNAL;
+            goto end;
+        }
+        drm_desc->layers[i].nb_planes = mod_props->drmFormatModifierPlaneCount;
+        av_free(modp.pDrmFormatModifierProperties);
+
+        if (drm_desc->layers[i].nb_planes > MAX_MEMORY_PLANES) {
+            av_log(hwfc, AV_LOG_ERROR, "Too many memory planes for DRM format!\n");
+            err = AVERROR_EXTERNAL;
+            goto end;
+        }
+
+        for (int j = 0; j < drm_desc->layers[i].nb_planes; j++) {
+            VkSubresourceLayout layout;
+            VkImageSubresource sub = {
+                .aspectMask = plane_index_to_aspect(j),
+            };
+
+            drm_desc->layers[i].planes[j].object_index = FFMIN(i, drm_desc->nb_objects - 1);
+
+            vk->GetImageSubresourceLayout(hwctx->act_dev, f->img[i], &sub, &layout);
+            drm_desc->layers[i].planes[j].offset = layout.offset;
+            drm_desc->layers[i].planes[j].pitch  = layout.rowPitch;
+        }
 
         if (drm_desc->layers[i].format == DRM_FORMAT_INVALID) {
             av_log(hwfc, AV_LOG_ERROR, "Cannot map to DRM layer, unsupported!\n");
@@ -3870,14 +3932,10 @@ static int vulkan_map_to_drm(AVHWFramesContext *hwfc, AVFrame *dst,
             goto end;
         }
 
-        drm_desc->layers[i].planes[0].object_index = FFMIN(i, drm_desc->nb_objects - 1);
 
         if (f->tiling == VK_IMAGE_TILING_OPTIMAL)
             continue;
 
-        vk->GetImageSubresourceLayout(hwctx->act_dev, f->img[i], &sub, &layout);
-        drm_desc->layers[i].planes[0].offset = layout.offset;
-        drm_desc->layers[i].planes[0].pitch  = layout.rowPitch;
     }
 
     dst->width   = src->width;
-- 
2.49.0

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