frontends/va: Support VA_PICTURE_H264_NON_EXISTING.

intel/libva#836
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31368

Author: dancingmirrors

src/gallium/frontends/va/picture_h264.c

@@ -30,6 +30,10 @@
 #include "util/u_handle_table.h"
 #include "va_private.h"
 
+#ifndef VA_PICTURE_H264_NON_EXISTING
+#define VA_PICTURE_H264_NON_EXISTING 0x00000020
+#endif
+
 static void resetReferencePictureDesc(struct pipe_h264_picture_desc *h264,
                                       unsigned int i)
 {
@@ -142,6 +146,8 @@ void vlVaHandlePictureParameterBufferH264(vlVaDriver *drv, vlVaContext *context,
          !!(h264->ReferenceFrames[i].flags & VA_PICTURE_H264_TOP_FIELD);
       context->desc.h264.bottom_is_reference[i] = !top_or_bottom_field ||
          !!(h264->ReferenceFrames[i].flags & VA_PICTURE_H264_BOTTOM_FIELD);
+      context->desc.h264.is_non_existing[i] =
+         !!(h264->ReferenceFrames[i].flags & VA_PICTURE_H264_NON_EXISTING);
       context->desc.h264.field_order_cnt_list[i][0] =
          top_or_bottom_field != VA_PICTURE_H264_BOTTOM_FIELD ?
          h264->ReferenceFrames[i].TopFieldOrderCnt: INT_MAX;

src/gallium/include/pipe/p_video_state.h

@@ -454,6 +454,7 @@ struct pipe_h264_picture_desc
    bool     is_long_term[16];
    bool     top_is_reference[16];
    bool     bottom_is_reference[16];
+   bool     is_non_existing[16];
    uint32_t field_order_cnt_list[16][2];
    uint32_t frame_num_list[16];