Film-Tech Forum ARCHIVE: how does HDMI prevent piracy?

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Posted by Scott Norwood (Member # 30) on 06-08-2008, 07:26 AM:

Stupid question: what, exactly, is the point of using HDMI instead of, say, HD-SDI on consumer-grade equipment? I thought that it was an anti-piracy thing, but AJA and others make boxes (boxen?) that convert HDMI to HD-SDI. At that point, anything can be easily copied to any device that accepts an HD-SDI input.

So why do Blu-Ray players (etc.) use HDMI instead of HD-SDI (or some other interface that is more reliable than HDMI), then?

Posted by Robert Minichino (Member # 3495) on 06-08-2008, 09:56 AM:

The "anti-piracy" part of HDMI is HDCP, which isn't supported by HD-SDI or HDMI to HD-SDI converters. This means the HDMI+HDCP source will only allow "unprotected" content to be sent to your HDMI to HD-SDI converter. [Frown]

HDMI uses a differential current signaling over inexpensive twisted-pair cable (like DVI), but is limited to the distances it can span. HD-SDI obviously uses twin coax (which is a bit more expensive and bulkier), and can be extended to 100m with equalization.

Posted by Scott Norwood (Member # 30) on 06-08-2008, 10:28 AM:

Ah, this makes sense. I didn't realize that the HDMI->HD-SDI box didn't pass flagged content.

So, how much HDMI content is flagged? What about Blu-Ray? Are all disks flagged or not?

Posted by Robert Minichino (Member # 3495) on 06-08-2008, 11:07 AM:

I think all players sending HD content over a digital connection will require HDCP compliant receiving devices for any output, but I haven't actually tried. [Smile]

For analog signals there's also the ICT (Image Constraint Token) which signals the player to down-rez the analog outputs, but there's an agreement in the industry not to set it on any media until about 2010.

There are less-than-legitimate HDMI "HDCP strippers" floating about if this is a problem. I don't expect these to go away unless HDCP gets a non-backwards-compatible revision to fix its cryptographic vulnerabilities.

And it's not that the HDMI->HD-SDI box won't pass the flagged content, but rather that if the player can't authenticate the display/receiver it just refuses to output video.

Posted by Chris Slycord (Member # 4239) on 06-08-2008, 12:57 PM:

quote: Robert Minichino
I think all players sending HD content over a digital connection will require HDCP compliant receiving devices for any output, but I haven't actually tried.

No. They'll simply run it at a lower resolution.

For instance, if you had a monitor that supports high enough resolutions for HD-content but doesn't support HDCP, you will get output just not at full, HD resolution.

Posted by Robert Minichino (Member # 3495) on 06-09-2008, 09:32 AM:

I just tried hooking my DVI-input non-HDCP monitor to my PS3's HDMI output, and just got black. I think the down-rezing is only for the analog outputs, and even that's not enabled yet.

Posted by Chris Slycord (Member # 4239) on 06-09-2008, 10:46 AM:

"all players" != "playstation 3"

The different manufactuers apparently each choose their own way of doing this; some choose to downres and others choose to say "you can't play this."

And what's really funny is I read that there are playstation 3 GAMES that require hdcp. It's one thing to do that with movies... but why on their games?

Posted by Charles Greenlee (Member # 3856) on 06-18-2008, 11:22 PM:

Cause we're dealing with 21st century Nazis. Better lern to goose step. Limiting the devices and media to depend solely on HDCP, and barring them from older or analog devices would cut into what I can enjoy for sure. While I have acess to other TV's, the only TV to my name isn't even cable ready. Though works good if adapted with something like a VCR, or a converter. Better than some current analog TVs. My monitor is an analog CRT. I'm just poor. :-p

Posted by Bobby Henderson (Member # 840) on 06-18-2008, 11:54 PM:

quote: Charles Greenlee
Cause we're dealing with 21st century Nazis. Better lern to goose step. Limiting the devices and media to depend solely on HDCP, and barring them from older or analog devices would cut into what I can enjoy for sure.

It bears repeating that no movie studio has released any movies on Blu-ray that utilize the Image Constraint Token. Viewers with an older HDTV with component inputs will still be able to see the movie in HD, not down-rezzed.

I have no problem with the notion of using copy protection on Blu-ray. I also get the feeling many of the people complaining about the copy protection on Blu-ray are among the crowd who believe they should be able to see and collect any and all movies free of charge.

My day job involves creating computer graphics. I have to send sketches to clients, usually in PDF. I take all kinds of steps to copy protect the artwork in those files -everything from password protecting the PDF to doing nasty stuff to the artwork the client won't notice but will create a major pain in the ass for any thieving rival wanting to reuse my original artwork for his own gain. I'm not working for free. No one is getting my artwork for free and getting paid from it either.

The aspects I do not like about the copy protection system on HDMI in general is it lays down the ground work for content creators to usher in a pay per every view model for movies and other forms of recorded entertainment. HDMI and LAN connected devices have a LOT of abuse potential.

If I buy a movie on disc I'm buying it once and that's it. I'm not paying for that same disc all over again at a later date. But the infrastructure was built into both high def movie disc formats for movie studios to pull such a stunt when they thought the time was safe enough to do so. I think movie fans need to make it clear to the studios they'll be very sorry if they move to that. We have not forgotten the shit pulled with DiVX.

Even the Image Constraint Token feature is a potential public relations disaster if it is ever put into effect. There's still a lot of HDTVs in service that lack HDMI connections or HDCP compliant DVI connections.

Image quality is another worthy gripe on copy protection. The encryption in formats like Blu-ray is not visible. Stuff like Cap Code on 35mm film prints or Macrovision on old analog tapes is visible.

quote: Charles Greenlee
While I have acess to other TV's, the only TV to my name isn't even cable ready. Though works good if adapted with something like a VCR, or a converter. Better than some current analog TVs. My monitor is an analog CRT.

I guess the HDMI issue doesn't affect you yet, Charles. Most new movie disc playback devices, even a lot of Blu-ray players and PS3, have legacy connections like composite and S-Video to support old NTSC TV sets. You just won't get anything "HD" over those connections, and may have to set up the device to output 480p as well.

Posted by Blaine Young (Member # 3992) on 06-19-2008, 04:13 PM:

I have a Panasonic DMP-BD10 player. The HDMI output works fine with an HDMI-DVI adapter on my Panasonic TV, but the same interface does not work on the EIKI projectors at the theater. I just get black - and this is without a disc in the player.

Posted by Steve Guttag (Member # 268) on 06-19-2008, 05:31 PM:

Blaine,

DVI (and HDMI) do a handshake to come up with a least common denominator resolution. If there is no intersection on the list of what the two can do...you get nothing. My suspicion is that your Eiki does not have on its list of DVI supported resolutions, one that your player can output.

Even if the projector understands 1080i, 720p...etc it likey does not on the DVI connector...which probably only understands a handful of computer rates...like 1024x768 (DXGA)...etc. It is even less likely that it would understand anything with 24p.

Steve

Posted by Blaine Young (Member # 3992) on 06-19-2008, 06:23 PM:

This is what I figured, and ended using component video instead. I just wanted to throw it out that simply because the devices can be connected together, they may not always work.

Posted by Leo Enticknap (Member # 534) on 06-24-2008, 01:45 AM:

quote: Steve Guttag
Even if the projector understands 1080i, 720p...etc it likey does not on the DVI connector...which probably only understands a handful of computer rates...like 1024x768 (DXGA)...etc. It is even less likely that it would understand anything with 24p.

Thanks for that - it would explain a problem I've been having recently with an upconverting DVD player (a Samsung 1080P7). Connecting it using an HDMI-DVI lead to an XGA video projector, it won't pass a digital signal in anything other than the DVD's native resolution (576p) - pressing the 'upconvert' button does nothing. Given that the projector is supposed to have a native resolution of 1,024 x 768 and accept inputs of up to 1,280 x 1,024, I was wondering why I couldn't get it to accept an upconverted picture from the player. That's probably why - the upconverted resolution doesn't correspond to the computer display resolutions it's expecting on the DVI input.

The HDCP thing is annoying as well. The projector is not HDCP compliant, and the player appears to trigger it with any disc that is CSS-encoded. So in order to view these discs I have to make a decrypted copy (usually on a DVD-RW which gets overwritten with the next film) simply in order to watch the content.

Posted by Tristan Lane (Member # 1169) on 06-24-2008, 04:38 AM:

Do a google search for "Naughty Boxes" or follow this link:

AVS Forum Thread

I can say from experience that certain models mentioned work. The reason for use was to be able to interface an HDCP signal to a CP2000.

It appears that these so called "converters" are becoming harder and harder to find.