[mythtv-users] Time Warner & Firewire

Brad Templeton brad+myth at templetons.com
Wed May 18 18:14:57 UTC 2005


On Wed, May 18, 2005 at 11:49:07AM -0600, Robert Johnston wrote:
> <snip />
> 
> Would it be possible for someone to, say, sign the NDA, and write a
> Closed Source/Binary-Only "Input plugin" for MythTV that handles 5C
> (Like the MS Exchange connector for Evolution)?

Generally there is a "robustness" requirement on tools with 5C or similar
DRM licences.    You can't allow untrusted components or software access
to the unencrypted video.   So it can't be an "input plugin" in an
open system.   

Instead, it would have to be a complex plugin that performed all functions
that need access to the video stream, or a set of them.   In a prior
message I noted what many of those functions are.   It would have to
output directly to the hardware of the video card (analog only, no DVI)
since playback of course needs access to the video.   It could not,
for example, use an untrusted device driver to output to the video card
because that might be a fake driver just copying the frames.

This is a problem because NVIDIA doesn't release the specs for high
performance driving of their video cards, so we run their proprietary
drivers.   So they would have to join the game too.

Even with all this it's an interesting debate about whether this
plugin would meet the robustness tests, since linux allows you to
instrument binary code for debugging, and it would not take long for
somebody to provide a patch that streams out the clear bytes.

For example, for Tivo to meet the requirements of DirecTV, they had
to put in a mechanism that checksummed the kernel on booting to make
sure it was a signed kernel and root FS from Tivo.  People got around
this, but with difficulty, and even then the video files on disk are
encrypted there.   However, this did not cause Tivo to be shut down by
DirectTV (one hopes), that happened for other reasons.   The Tivo
is in a sealed box with a Torx bit, for some reason that helps your
robustness even though you can buy those bits anywhere.



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