Systems, methods, devices, and processors are described for packet clustering and frame formation in ACM systems. A stream of packets may be received at a gateway. During each cycle, a group of packets from the stream may be fetched according to QoS parameters. The group of packets may be clustered according to modcode to produce a packet list. In some embodiments, packets may be arranged and grouped according to transport steam identifier and modcode to produce a packet list. The packet lists may be clustered sequentially from lower order modcode to higher order modcode. Various frame packing techniques are also described.