Re: www.badvista.org

From: Damien Hull <dhull@digitaloverload.net>
Date: Mon Jul 09 2007 - 15:55:24 AKDT

Alan C. wrote:
> I'm not 100% on this one but here is how I understand it and why
> there might be some confusion here. Note I haven't checked out any of
> the links below but have spent significant time mucking with high
> definition sources so this should apply to HD in general, not
> necessary Linux compatible HD devices:
>
> Most modern hardware implementations of digital HD content have some
> sort of DRM required. It maybe that some of the HD recording devices/
> software for Linux don't support modern DRM (HDCP in this case) and
> therefore can't record the content unless the provider (cable company/
> satellite provider/Blu-ray player, etc.) disables the HDCP
> negotiation. If HDCP is disabled then the receiving device can record
> the content but many of the hardware vendors are now requiring that
> HDCP be enabled and one by one cable/sat/etc. companies are enabling
> HDCP on their platforms.
>
> HDMI (and DVI in some cases) uses a protocol called HDCP in order to
> prevent unauthorized devices from receiving the high definition
> content stream. When the HDMI source is turned on it negotiates with
> the next HDMI aware device, etc. down the chain all the way to the
> recorder or display device. If a single device (other than a plain no-
> logic switch/relay) in-between doesn't support HDMI or they are
> running incompatible versions you will end up with no audio or video
> being transmitted since the entire chain must be authenticated for
> the video and audio to be sent over HDMI.
>
> One of the ways I avoided DRM early on when I didn't have HDCP
> compatible devices was to use source devices that did not enforce
> HDCP. Normally the combination that I used was SPDIF audio w/ DVI or
> Component video. Now I've given up and almost all my devices support
> HDCP since it was becoming increasingly difficult to integrate new
> components without it.
>
> Component, VGA/HD-15, DVI (in some cases - modern DVI interfaces are
> commonly HDCP enabled), analog audio, SPDIF/Coax interfaces etc. are
> all sources which do not have HDCP so this makes it so if you can get
> into the middle or have a device hanging off the cable or sat box you
> can record the content in high definition. Many people that
> experience compatibility issues with HDMI/HDCP between their products
> end up switching back to Component video and non-HDMI digital audio
> in order to record or display high definition content.
>
> -Alan
>
>
This is good stuff. I'm still a little confused about encrypted and
unencrypted content and HDCP.

    * Can you capture true HD content from GCI Cable?
    * Can you play encrypted content under Linux?
    * Does HDCP hardware work with Linux?

I should point out that I don't have any HD hardware. What I know is
only what I've heard.

I found this: http://www.mythtv.org/wiki/index.php/Configuring_HDTV

          HDTV on Cable

    Its standard is called QAM
    <http://www.mythtv.org/wiki/index.php/QAM> ATSC. Many of the OTA
    Tuner cards like AirStar HD-5000 or PcHDTV work with Clear
    (unencrypted) QAM. It just takes a little bit more time and energy
    getting it to work. Verizon FIOS also uses QAM for its unencrypted
    channels.

    [edit
    <http://www.mythtv.org/wiki/index.php?title=Configuring_HDTV&action=edit&section=6>]

          HDTV and Satellite TV

    All channels off of Satellite are digital but not all of them are in
    HDTV Format. Most are Encrypted but not all of them (For example
    LyngSat Free OTA <http://www.lyngsat.com/freetv/United-States.html>).

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Received on Mon Jul 9 15:55:56 2007

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