Exercise video switching and backpressure in a real call

src/call/call_video_transport.c

@@ -76,7 +76,8 @@ static void flush(struct call_video_transport *v) {
     uint8_t wire[CALL_VIDEO_HEADER_BYTES + CALL_VIDEO_FRAGMENT_BYTES];
     // Ограниченный burst одного вызова; повторяется по audio send и таймеру 50мс.
     for (unsigned budget = 0; v->data && budget < 16; budget++) {
-        if (!etcp_router_send_q_has_room(s->ctx->inst, s->group_id, s->peer_node_id, ETCP_RT_ID_CALL_VIDEO)) return;
+        if (!etcp_router_send_q_has_room(s->ctx->inst, s->group_id, s->peer_node_id, ETCP_RT_ID_CALL_VIDEO)
+            || queue_entry_count(conn->send_q) >= ROUTER_MAX_SEND_Q_PACKETS) return;
         uint32_t remaining = v->tx.size - v->tx.offset;
         v->tx.length = remaining < CALL_VIDEO_FRAGMENT_BYTES ? remaining : CALL_VIDEO_FRAGMENT_BYTES;
         v->tx.data = v->data + v->tx.offset;