diff --git a/src/gallium/drivers/radeonsi/mm/radeon_vcn_enc.c b/src/gallium/drivers/radeonsi/mm/radeon_vcn_enc.c
index e945d9f44d7..ae88f5874fe 100644
--- a/src/gallium/drivers/radeonsi/mm/radeon_vcn_enc.c
+++ b/src/gallium/drivers/radeonsi/mm/radeon_vcn_enc.c
@@ -444,12 +444,18 @@ static void radeon_vcn_enc_h264_get_slice_ctrl_param(struct radeon_encoder *enc,
                                                 enc->enc_pic.quality_modes.pre_encode_mode) &&
        pic->num_slice_descriptors <= RENCODE_MAX_NUM_SLICES)
    {
-      enc->enc_pic.slice_ctrl.slice_control_mode = RENCODE_H264_SLICE_CONTROL_MODE_VARIABLE_MBS;
+      uint32_t cumulative_mbs = 0;
       enc->enc_pic.h264_slice_info_var.num_slices = pic->num_slice_descriptors;
       for (unsigned i = 0; i < pic->num_slice_descriptors; i++) {
          enc->enc_pic.h264_slice_info_var.slice_info[i].num_mbs_per_slice =
             pic->slices_descriptors[i].num_macroblocks;
+         cumulative_mbs += pic->slices_descriptors[i].num_macroblocks;
       }
+
+      /* If the app input does not fill the frame, override it by not using
+       * variable slice mode. */
+      if (cumulative_mbs == num_mbs_total)
+         enc->enc_pic.slice_ctrl.slice_control_mode = RENCODE_H264_SLICE_CONTROL_MODE_VARIABLE_MBS;
    }
 }
 
@@ -828,13 +834,19 @@ static void radeon_vcn_enc_hevc_get_slice_ctrl_param(struct radeon_encoder *enc,
                                                 enc->enc_pic.quality_modes.pre_encode_mode) &&
        pic->num_slice_descriptors <= RENCODE_MAX_NUM_SLICES)
    {
-      enc->enc_pic.hevc_slice_ctrl.slice_control_mode = RENCODE_HEVC_SLICE_CONTROL_MODE_VARIABLE_CTBS;
+      uint32_t cumulative_ctbs = 0;
       enc->enc_pic.hevc_slice_info_var.num_slice_segments = pic->num_slice_descriptors;
       for (unsigned i = 0; i < pic->num_slice_descriptors; i++) {
          enc->enc_pic.hevc_slice_info_var.slice_segment_info[i].num_ctbs_per_segment =
             pic->slices_descriptors[i].num_ctu_in_slice;
          enc->enc_pic.hevc_slice_info_var.slice_segment_info[i].is_independent = 1;
+         cumulative_ctbs += pic->slices_descriptors[i].num_ctu_in_slice;
       }
+
+      /* If the app input does not fill the frame, override it by not using
+       * variable slice mode. */
+      if (cumulative_ctbs == num_ctbs_total)
+         enc->enc_pic.slice_ctrl.slice_control_mode = RENCODE_HEVC_SLICE_CONTROL_MODE_VARIABLE_CTBS;
    }
 }