[mythtv] Solution to CableCARD problem?
Rudy Zijlstra
mythtv at grumpydevil.homelinux.org
Sun Jul 8 19:15:41 UTC 2007
Tim Moore wrote:
>
> I’m new to MythTV, so please excuse me if this has already been
> addressed. I understand the problem with CableLabs certification, and
> how it will be impossible for an open source solution to obtain it.
> However, I’ve been doing a lot of research into this, and it seems to
> me that there is a solution that has been overlooked.
>
> CableLabs won’t certify a MythTV solution because it would be
> impossible in an open source solution to prevent access to the
> decrypted video stream. The reason that Vista can obtain it is because
> of the closed DRM implementation that MS has built into the operating
> system and into Windows Media Player. There really is no way to get
> around this CableLabs requirement, so I propose that the solution is a
> modified architecture for MythTV that will works with it.
>
> Essentially, the video path and the control path of the system need to
> be separated. The video path needs to be closed and “secure” (or, that
> is, meet CableLabs requirements. We all know that nothing is 100%
> secure.). It is not good enough to use some video adapter with
> CableCARD slots (such as the ATI card that Dell is using for its
> premium cable-ready TV), which decrypts the video signal and passes it
> to the operating system and media player software. This approach, as
> we have seen, requires CableLabs to trust the operating system, the
> media center software, and the hardware. For the ATI card to work on
> the Dell system, the ATI drivers (written by Microsoft, by the way)
> check for a code in the BIOS to confirm that it is connected to
> approved hardware. Getting CableLabs certification costs over $100,000
> per system, so this approach rules out small system builders, even if
> they are using Vista. For open source solutions, it rules it out
> altogether.
>
> However, we are starting to see hardware manufacturers build
> single-chip DVR solutions. The Broadcom BCM7118
> <http://www.broadcom.com/products/Cable/Cable-Set-Top-Box-Solutions/BCM7118>
> is one such device. This board contains not only a CableCARD
> interface, but also DCAS support which should eventually supersede
> CableCARD with a downloadable conditional access system (reducing the
> high upgrade and support costs for cable companies, and/or users,
> caused by the current hardware-only solution). The BCM7118 interfaces
> directly to its own hard disk, securely storing encrypted programming.
> It contains all the critical components of a premium cable-ready DVR;
> authentication, authorization, decryption, decoding, storage,
> graphics, sound and control. You can make a stand-alone DVR from this
> system, with the addition of a case, hard disk, and some basic
> supporting electronics. As a complete and closed system,
> theoretically, the BCM7118 should be able to achieve CableLabs
> certification. However, I haven’t seen it on the CableLabs approved
> list so I have emailed Broadcom to find out. I’ll let you know what I
> hear… Hopefully, it’s in the works.
>
You will never see the BCM7118 on that list. What you will see is a
product based on it. Same goes for the 7400, which is essentially a HD
STB (though it still needs a frontend = tuners).
> The BCM7118 supports an API that allows a connected system to control
> it. So, MythTV could be modified to use this API to control the
> BCM7118. I’m sure there must be a graphics card out there that can
> take the output of the BCM7118 and superimpose on it graphics from the
> PC, thereby adding a capability to add EPG and other graphics from
> MythTV. Since the decrypted TV signal is not passed to the MythTV
> software or operating system, there is no risk of it being copied.
> That is, no more than the output of any other cable box…
>
> So, the solution is not to make decryption part of a MythTV system,
> but to make MythTV a control solution for a bare-bones DVR that is
> installed inside the PC chassis. Of course, MythTV could still work in
> the traditional mode for unencrypted media. I realize that this means
> that the entire solution is no longer 100% open source, but then what
> system is when you take into account the firmware in the supporting
> hardware? The important thing is that all of the high-level control
> software remains open source, and that is where the value is added.
>
> There is still one small snag. Broadcom doesn’t yet make a single-chip
> system with HD output (although it can downscale HD to SD). I’m sure
> that can’t be too far away, and I have emailed them to find out.
>
Be very curious if you get an answer...
> I think that if the development community can get behind this (and if
> CableLabs will certify single-chip/board DVRs, as I hope) then MythTV
> can remain a viable alternative to Vista. If not, then it will surely
> die as new cheaper alternatives to Tivo become available and more
> Vista systems get certified.
>
>
I do not agree with this last assessment. If that were true Myth would
have died long ago.
Different usage pattern and requirements.
Cheers,
Rudy
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