Comcast Corp. (Nasdaq: CMCSA, CMCSK) has its first all-IP set-top box on the roadmap, Light Reading Cable has learned.

Industry sources say the model, referred to as the X3, is an IP-based, HD client device that's capable of running Comcast's new cloud-based navigation system and handling future services, including a network DVR. (See Comcast Explores Network DVRs and Comcast to Run Small Net-DVR Trial .)

The box appears to be the latest device tagged for Xcalibur, Comcast's next-gen video platform. The first product to come out of that project is the Pace plc -made X1, a hybrid QAM/IP video gateway equipped to support the MSO's new navigation system while opening the door to third-party applications such as Pandora Media Inc. and Facebook . Comcast is testing the X1 in Augusta, Ga., though sources say the MSO expects to start expanding those tests into at least one more market by May. (See Comcast to Swing Xcalibur Wide in 2012.)

How the X3 will source linear and on-demand video in the early going was not immediately known. However, its appearance on the roadmap suggests that Comcast may be pursuing the deployment of an IP video simulcast. While the amount of bandwidth required for that seems to vary, cable engineers have indicated recently that an MSO might need to carve out 24 to 32 channels to produce a full IP simulcast. Comcast is already in the process of reclaiming all of its analog spectrum to apply toward HD programming and new services like Xcalibur. (See MSOs Must Bust Out Bandwidth for IP Video Leap and Comcast Starts to Kiss Analog TV Goodbye.)

If the X3 is compatible with a future version of the X1 that includes real-time video transcoding, it's also been suggested that the X1 gateway could convert incoming QAM video into IP and shuttle those streams to the X3 using Multimedia over Coax Alliance (MoCA) .

But a pairing of the X1 and X3 isn't expected to happen for a while. An industry source says the first multi-room DVR implementation involving the X1 will team the hybrid device with the RNG150, an all-digital HD client box made by vendors such as Motorola Mobility LLC , with trials expected late this year.

The RNG150 (here's some data (PDF)) supports MPEG 2/4 and MoCA, and it sports an embedded Docsis modem. With the addition of new software and firmware, Comcast's RNG boxes can be "flipped" to become IP video-capable. (See Comcast 'RNG' Set-Tops Have IPTV Potential .)

It's not clear when Comcast will introduce the X3, though it's not expected until late 2012 or sometime next year. A person familiar with the project said several chip makers, including Marvell Technology Group Ltd. (Nasdaq: MRVL), Broadcom Corp. (Nasdaq: BRCM), Entropic Communications Inc. (Nasdaq: ENTR) (now that it's acquired Trident's set-top chip business) and Intel Corp. (Nasdaq: INTC), could be in the running to power the new all-IP box. The initial version of the X1 uses an Intel chipset. (See Comcast Confirms Xcalibur Partners and Entropic Takes $55M Stab at Trident.)

— Jeff Baumgartner, Site Editor, Light Reading Cable