diff --git a/src/h264.c b/src/h264.c
index 7d20a98..6efacb2 100644
--- a/src/h264.c
+++ b/src/h264.c
@@ -632,6 +632,38 @@ int h264_set_controls(struct request_data *driver_data,
 			      &surface->params.h264.slice,
 			      &surface->params.h264.picture, &slice, &weights);
 
+	/*
+	 * Derive PFRAME / BFRAME flags in v4l2_ctrl_h264_decode_params.flags
+	 * from VASliceParameterBufferH264.slice_type. VAAPI's slice_type
+	 * matches the H.264 spec slice_type semantic: 0=P, 1=B, 2=I, 3=SP,
+	 * 4=SI; values 5..9 mean "all slices in the picture have this
+	 * slice_type" (mod 5 yields the underlying type). VAAPI consumers
+	 * (ffmpeg, mpv) populate this for every slice; in FRAME_BASED mode
+	 * we only see the most-recent slice's params, but slice_type is
+	 * uniform across a single coded picture for our purposes.
+	 *
+	 * Kernel consumers that read these flags: tegra-vde
+	 * (drivers/media/platform/nvidia/tegra-vde/h264.c lines 783-799 of
+	 * 6.19.x) selects the inter-frame decode kernel. Hantro / rkvdec /
+	 * cedrus / mediatek / qcom-iris-stateless do not consume them.
+	 * Setting them keeps the libva-v4l2-request fork upstreamable
+	 * across drivers without affecting hantro behaviour.
+	 *
+	 * Cross-reference: ext-ctrls-codec-stateless.rst Decode Parameters
+	 * Flags — V4L2_H264_DECODE_PARAM_FLAG_PFRAME / _BFRAME.
+	 */
+	switch (surface->params.h264.slice.slice_type % 5) {
+	case H264_SLICE_P:
+		decode.flags |= V4L2_H264_DECODE_PARAM_FLAG_PFRAME;
+		break;
+	case H264_SLICE_B:
+		decode.flags |= V4L2_H264_DECODE_PARAM_FLAG_BFRAME;
+		break;
+	default:
+		/* I / SP / SI: no extra flag. */
+		break;
+	}
+
 	sps.profile_idc = h264_profile_to_idc(profile);
 
 	/*