diff --git a/apps/signer/gst-plugin/gstsigning.c b/apps/signer/gst-plugin/gstsigning.c
index a0a2ec8..49c7efb 100644
--- a/apps/signer/gst-plugin/gstsigning.c
+++ b/apps/signer/gst-plugin/gstsigning.c
@@ -164,55 +164,46 @@ create_buffer_with_current_time(GstSigning *signing)
   return buf;
 }
 
-static void
-free_nalu_data(gpointer data)
-{
-  signed_video_nalu_data_free(data);
-}
-
-/* Prepend NALUs according to results from Signed Video lib calls. Returns the number of NALUs
- * that were prepended to |current_au|, or -1 on error. */
+/* Prepend seis fetched from Signed Video lib.
+ * Returns the number of nalus that were prepended to @current_au,
+ * or -1 on error. */
 static gint
-prepend_nalus(GstSigning *signing, GstBuffer *current_au)
+get_and_add_sei(GstSigning *signing, GstBuffer * current_au, gint idx, const guint8 * peek_nalu, gsize peek_nalu_size)
 {
-  SignedVideoReturnCode sv_rc = SV_UNKNOWN_FAILURE;
-  signed_video_nalu_to_prepend_t nalu_to_prepend = {0};
+  SignedVideoReturnCode sv_rc;
   gint prepend_count = 0;
-
-  sv_rc = signed_video_get_nalu_to_prepend(signing->priv->signed_video, &nalu_to_prepend);
-  while (sv_rc == SV_OK && nalu_to_prepend.prepend_instruction != SIGNED_VIDEO_PREPEND_NOTHING) {
-    gpointer data = nalu_to_prepend.nalu_data;
-    gsize size = nalu_to_prepend.nalu_data_size;
+  guint8 *sei = NULL;
+  gsize sei_size = 0;
+
+  /* Brief description of API. For more details see the public header file.
+   * SignedVideoReturnCode
+   * signed_video_get_sei(signed_video_t *self, uint8_t **sei, size_t *sei_size,
+   *     unsigned *payload_offset, const uint8_t *peek_nalu,
+   *     size_t peek_nalu_size, unsigned *num_pending_seis); */
+  sv_rc = signed_video_get_sei (signing->priv->signed_video, &sei, &sei_size, NULL, peek_nalu, peek_nalu_size, NULL);
+  while (sv_rc == SV_OK && sei_size > 0 && sei) {
     GstMemory *prepend_mem;
 
-    // Write size into NALU header. The size value should be the data size, minus the size of the
-    // size value itself
-    GST_WRITE_UINT32_BE(data, size - sizeof(guint32));
-
-    GST_DEBUG_OBJECT(signing, "create a %" G_GSIZE_FORMAT "bytes nalu to prepend", size);
-    prepend_mem = gst_memory_new_wrapped(0, data, size, 0, size, data, free_nalu_data);
-
-    switch (nalu_to_prepend.prepend_instruction) {
-      case SIGNED_VIDEO_PREPEND_NALU:
-        GST_DEBUG_OBJECT(signing, "prepend nalu to current AU");
-        gst_buffer_prepend_memory(current_au, prepend_mem);
-        prepend_count++;
-        break;
-      default:
-        GST_FIXME_OBJECT(
-            signing, "unsupported prepend instruction %d", nalu_to_prepend.prepend_instruction);
-        break;
-    }
+    /* Write size into nalu header. The size value should be the data size,
+     * minus the size of the size value itself. */
+    GST_WRITE_UINT32_BE(sei, (guint32)(sei_size - sizeof(guint32)));
+
+    GST_DEBUG_OBJECT(signing, "preped sei of size %" G_GSIZE_FORMAT " to current AU", sei_size);
+    prepend_mem = gst_memory_new_wrapped(0, sei, sei_size, 0, sei_size, sei, g_free);
+    gst_buffer_insert_memory(current_au, idx, prepend_mem);
+    prepend_count++;
 
-    sv_rc = signed_video_get_nalu_to_prepend(signing->priv->signed_video, &nalu_to_prepend);
+    sv_rc = signed_video_get_sei(signing->priv->signed_video, &sei, &sei_size, NULL, peek_nalu, peek_nalu_size, NULL);
   }
 
-  if (sv_rc != SV_OK) goto get_nalu_failed;
+  if (sv_rc != SV_OK) {
+    goto get_sei_failed;
+  }
 
   return prepend_count;
 
-get_nalu_failed:
-  GST_ERROR_OBJECT(signing, "signed_video_get_nalu_to_prepend failed");
+get_sei_failed:
+  GST_ERROR_OBJECT(signing, "signed_video_get_sei failed");
   return -1;
 }
 
@@ -224,7 +215,7 @@ gst_signing_transform_ip(GstBaseTransform *trans, GstBuffer *buf)
   guint idx = 0;
   GstMemory *nalu_mem = NULL;
   GstMapInfo map_info;
-  gint prepend_count = 0;
+  gboolean got_sei = false;
 
   priv->last_pts = GST_BUFFER_PTS(buf);
   // last_pts is an GstClockTime object, which is measured in nanoseconds.
@@ -242,6 +233,26 @@ gst_signing_transform_ip(GstBaseTransform *trans, GstBuffer *buf)
       goto map_failed;
     }
 
+    /* SEIs generated by the Signed Video lib should be passed in as any nalu. The reason
+     * for this is that not all are signed and hence 'floating around' in the stream.
+     * Therefore, pull and add them before adding the current nalu. */
+    gint add_count = get_and_add_sei(signing, buf, idx, &(map_info.data[4]), map_info.size - 4);
+    if (add_count < 0) {
+      GST_ELEMENT_ERROR(signing, STREAM, FAILED, ("failed to add nalus"), (NULL));
+      goto get_and_add_sei_failed;
+    }
+    if (add_count > 0) {
+      gst_memory_unmap(nalu_mem, &map_info);
+      /* Get the newly added seis. They need to be added for signing like any other
+       * Bitstream Unit. */
+      nalu_mem = gst_buffer_peek_memory(buf, idx);
+      if (G_UNLIKELY(!gst_memory_map(nalu_mem, &map_info, GST_MAP_READ))) {
+        GST_ELEMENT_ERROR(signing, RESOURCE, FAILED, ("Failed to map memory"), (NULL));
+        goto map_failed;
+      }
+      got_sei = true;
+    }
+
     // Depending on bitstream format the start code is optional, hence libsigned-video supports
     // both. Therefore, since the start code in the pipeline temporarily may have been replaced by
     // the picture data size this format is violated. To pass in valid input data, skip the first
@@ -254,19 +265,12 @@ gst_signing_transform_ip(GstBaseTransform *trans, GstBuffer *buf)
       goto add_nalu_failed;
     }
 
-    prepend_count = prepend_nalus(signing, buf);
-    if (prepend_count < 0) {
-      GST_ELEMENT_ERROR(signing, STREAM, FAILED, ("failed to prepend nalus"), (NULL));
-      goto prepend_nalus_failed;
-    }
-
     gst_memory_unmap(nalu_mem, &map_info);
 
-    idx += prepend_count;  // Move past prepended nalus
     idx++;  // Go to next nalu
   }
 
-  if (prepend_count > 0) {
+  if (got_sei) {
     // Push an event to produce a message saying SEIs have been added.
     GstStructure *structure = gst_structure_new(
         SIGNING_STRUCTURE_NAME, SIGNING_FIELD_NAME, G_TYPE_STRING, "signed", NULL);
@@ -275,11 +279,11 @@ gst_signing_transform_ip(GstBaseTransform *trans, GstBuffer *buf)
       GST_ELEMENT_ERROR(signing, STREAM, FAILED, ("failed to push message"), (NULL));
     }
   }
-  GST_DEBUG_OBJECT(signing, "push AU with %d nalus", gst_buffer_n_memory(buf));
+  GST_DEBUG_OBJECT(signing, "push AU with %d Bitstream Units", gst_buffer_n_memory(buf));
 
   return GST_FLOW_OK;
 
-prepend_nalus_failed:
+get_and_add_sei_failed:
 add_nalu_failed:
   gst_memory_unmap(nalu_mem, &map_info);
 map_failed:
@@ -298,8 +302,8 @@ push_access_unit_at_eos(GstSigning *signing)
   }
 
   au = create_buffer_with_current_time(signing);
-  if (prepend_nalus(signing, au) < 0) {
-    GST_ERROR_OBJECT(signing, "failed to prepend nalus");
+  if (get_and_add_sei(signing, au, 0, NULL, 0) < 0) {
+    GST_ERROR_OBJECT(signing, "failed to get SEIs");
     goto prepend_failed;
   }
 
@@ -363,13 +367,11 @@ setup_signing(GstSigning *signing, GstCaps *caps)
     GST_ERROR_OBJECT(signing, "could not create Signed Video object");
     goto create_failed;
   }
-  if (signed_video_generate_private_key(
-          SIGN_ALGO_ECDSA, PATH_TO_KEY_FILES, &private_key, &private_key_size) != SV_OK) {
+  if (signed_video_generate_ecdsa_private_key(PATH_TO_KEY_FILES, &private_key, &private_key_size) != SV_OK) {
     GST_DEBUG_OBJECT(signing, "failed to generate pem file");
     goto generate_private_key_failed;
   }
-  if (signed_video_set_private_key(
-          priv->signed_video, SIGN_ALGO_ECDSA, private_key, private_key_size) != SV_OK) {
+  if (signed_video_set_private_key_new(priv->signed_video, private_key, private_key_size) != SV_OK) {
     GST_DEBUG_OBJECT(signing, "failed to set private key content");
     goto set_private_key_failed;
   }
diff --git a/apps/validator/main.c b/apps/validator/main.c
index 6070b31..a85eb20 100644
--- a/apps/validator/main.c
+++ b/apps/validator/main.c
@@ -528,10 +528,10 @@ on_source_message(GstBus __attribute__((unused)) *bus, GstMessage *message, Vali
       }
       gint num_unsigned_gops = (data->invalid_gops || data->valid_gops_with_missing || data->valid_gops) ? 0 : data->no_sign_gops;
       if (is_unsigned) {
-        fprintf(f, "Number of unsigned NAL Units: %u\n", data->auth_report->accumulated_validation.number_of_received_nalus);
+        fprintf(f, "Number of unsigned Bitstream Units: %u\n", data->auth_report->accumulated_validation.number_of_received_nalus);
       } else {
         fprintf(f, "Number of valid GOPs: %d\n", data->valid_gops);
-        fprintf(f, "Number of valid GOPs with missing NALUs: %d\n", data->valid_gops_with_missing);
+        fprintf(f, "Number of valid GOPs with missing BUs: %d\n", data->valid_gops_with_missing);
         fprintf(f, "Number of invalid GOPs: %d\n", data->invalid_gops);
         fprintf(f, "Number of GOPs without signature: %d\n", num_unsigned_gops);
       }
diff --git a/test-files/signed_test_h264.mp4 b/test-files/signed_test_h264.mp4
index c4ca079..d35b8bf 100644
Binary files a/test-files/signed_test_h264.mp4 and b/test-files/signed_test_h264.mp4 differ