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Technical / Theoretical hurdles in _true_ HD recording ?

1395 Views 11 Replies 3 Participants Last post by timecop, Jan 18, 2007

jbrooks

Discussion Starter · Jan 15, 2007

Ok, let's say I don't want to mess around with a firewire dumping hack and worry about when my cable company will 5c my channels, wrecking my setup.

Let's also say I am sick of all the hacks for changing channels out of band (IR blasting, firewire channel changing, etc.)

Let's say that I am just sick and tired of all of the mumbo jumbo and terrible hacks that are involved with cable HD recording, all of which are half solutions _anyway_ because the "premium" channels are off limits regardless, and the cable company can wreck your setup anytime it wants to.

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Now, on to the technical / theoretical discussion. I'll try to phrase this question very clearly and shortly:

What technical hurdles and (theoretical) breaks in encryption, and possibly new hardware, would be required for me to plug my coax cable into my cap card and just record full resolution HDTV on any channel I pay for ?

I _realize_ that this is not currently possible.

I just know that the only sensible, useful TV recording setup I have ever had was with SDTV and a hauppage pvr-350. I plugged my coax cable into the card and _that was that_. No ridiculous out of band signaling, no worrying about which cable box firmware I had ... blah blah blah.

So let's just pretend I have unlimited funds and 20 hotshot finnish cryptographers working for me ... how would I (theoretically) make this happen ?

Is new hardware needed ? Or are modern cap cards capable of receiving (and changing channels on) digital cable TV ?

Does DTCP need to be broken, or is that just for firewire ? If it is just for firewire, what encryption are the cable companies using to encrypt the HD "premium" content ? Is it a different scheme for every provider, or is there a standard method to encrypt "premium" HD channels ?

Thanks. All comments and rambling appreciated.

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timecop

· #2 · Jan 16, 2007

You just need a fairly simple modification installed inside the receiver to grab decrypted MPEG2TS before it reaches the decoder chip.

Its silly simple to design and make, however, illegal to sell or advertise, on machines with "legal" 1394 outputs. This is why R5000HD is installed only in receivers without a 'copy protected' digital output.

This way lets you capture 'live' and is probably not what you want, but probably is the easiest thing to do and maintain.

Or you can buy Windows Vista, ATI's now-in-development cablecard-enabled capture card, and record DRM'd files.

You won't find a "legal" solution to do what you want, easily, AND without DRM. Not these days, anyway.

Encryption-wise, I think its DES for the audio/video payload scramble.

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HDTVFanAtic

· #3 · Jan 16, 2007

Quote:
Originally Posted by timecop /forum/post/0

You just need a fairly simple modification installed inside the receiver to grab decrypted MPEG2TS before it reaches the decoder chip.

Its silly simple to design and make, however, illegal to sell or advertise, on machines with "legal" 1394 outputs. This is why R5000HD is installed only in receivers without a 'copy protected' digital output.

This way lets you capture 'live' and is probably not what you want, but probably is the easiest thing to do and maintain.

Or you can buy Windows Vista, ATI's now-in-development cablecard-enabled capture card, and record DRM'd files.

You won't find a "legal" solution to do what you want, easily, AND without DRM. Not these days, anyway.

Encryption-wise, I think its DES for the audio/video payload scramble.

My understanding is that the decrypted MPEG2TS and decoder chip are on the same chip on S/A, Tivo Series 3 and the DirecTV MPEG4 units so that is not possible

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jbrooks

Discussion Starter · #4 · Jan 16, 2007

Ok, first off, I'm sorry I even need to clarify this, but "Windows DRM'd" files are not, of course, acceptable. I want to permanently archive media for use far into the future on whatever weirdo device I may have in 2045. And I don't use any windows systems anyway, so it's a moot point.

And no, as interesting as a chip-mod that intercepts pre-encrypted TS may be, it does not at all solve the problem - first off because you are dependent on your cable company to have and/or support (and not accidently break regularly with signal or updates) a cable box that is mod-able, and second, you still have to jump through ridiculous hacks to change the channel via out of band signaling.

So one of my questions: "what do cable companies use to encrypt premium digital HD channels" has been answered: DES.

My other questions remain:

- is that (DES) standard across all digital cable providers ?

- do existing HD cable capture cards have the ability to tune and change channels with a digital cable signal - assuming no set top box - just plug coax into the card ... ?

- if the answer is yes, will they record premium HD channels if I tell them to, even if they are encrypted ? That is, will they just record 30 minutes of encrypted gibberish, or will they refuse to record at all ?

Does DTCP/HDCP come into play at all if you break the DES on the coax ? Is it reasonable to consider breaking the DES on the coax as a shortcut to dealing with any of the "trusted device" protection like HDCP/DTCP ?

Again, any comments appreciated - I want to gain as deep of a theoretical understanding as I possibly can.

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timecop

· #5 · Jan 16, 2007

I've ran some tests with HDTVFusion5 card.

It will tune to a scrambled QAM channel with their software, and 'record' it to .tp/.ts file.

However, all it records is scrambled video, audio, PAT, PMT pid (those 4, only).

That means, it does not provide a way to descramble the signal (no ECM pid, no EMM, or any other method that is used to carry decryption keys/commands that are sent to cablecard(?) or smartcard to decrypt.

In TSReader it looks like: http://pbx.mine.nu/tsr-hdcable.png

Unless information needed to decrypt is contained in the two audio/video streams, or unless there's a way to capture 'full mux' as opposed to just filtered audio/video PIDs, there is not much that can be done to decrypt it.

hdtvfusion cards support QAM, but only in their software, not through BDA drivers/directshow. The PID filtering might be a limitation of their software.

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timecop

· #6 · Jan 16, 2007

Quote:
Originally Posted by jbrooks /forum/post/0

1. do existing HD cable capture cards have the ability to tune and change channels with a digital cable signal - assuming no set top box - just plug coax into the card ... ?

2 if the answer is yes, will they record premium HD channels if I tell them to, even if they are encrypted ? That is, will they just record 30 minutes of encrypted gibberish, or will they refuse to record at all ?

3. Does DTCP/HDCP come into play at all if you break the DES on the coax ? Is it reasonable to consider breaking the DES on the coax as a shortcut to dealing with any of the "trusted device" protection like HDCP/DTCP ?

1. hdtvfusion is one of them, there could be others.

2. yes, see previous post, but not in a very useful way.

3. no, it does not. and i guess you could say its a 'shortcut'.

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jbrooks

Discussion Starter · #7 · Jan 17, 2007

EDIT: timecop - I re-read your responses and it looks like this strategy won't work...I'd appreciate if you'd read this post, but I see that it is probably not workable...

thank you for the clarifications - I appreciate knowing that there are HD cap cards out there that can record encrypted "premium" channels - even if it means they are a garbled mess.

Here is a follow-up to that question - can I instruct a capture card like that to capture in raw format ? That is, NOT as an mpeg ?

I don't know if PCI is capable of that bandwidth, but PCI-X/E should be - I just need to have a fast disk array in the system to capture it all in real time.

If the card you mentioned cannot capture HDTV in raw format, do you know of one that can ?

The idea here is, if you tell your cap card to capture in raw format, then you can decrypt the resulting raw (large) video files, which, according to my understanding (and industry documentation) are encrypted in DES ... which is something a home computer can break.

Comments ?

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timecop

· #8 · Jan 17, 2007

The "raw" format isn't what you want. I'm assuming (without much data to back it up with) that non-filtered mpeg2ts recorded from cable DOES have all the required data to decrypt it.

DViCO card is probably filtering just video/audio PIDs as thats what you would normally record on a non-scrambled channel. There's probably a way to get to unfiltered TS via their SDK they're selling for $1k

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jbrooks

Discussion Starter · #9 · Jan 17, 2007

Wow - thank you - you have answered almost all of my questions.

So my next question - what do _you_ do ? How are _you_ recording "premium" HD channels ? Are you going the firewire route and just hoping they don't 5c them out ? Or something else ?

I know it sounds complex and difficult, but getting an altered firmware for a card to make it dump non-filtered mpeg2ts, and then cracking DES in real time _or_ in batch form later, is not a crazy thing to try to do ... I think it would be worth someone pursuing...

What do you think ?

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timecop

· #10 · Jan 17, 2007

I take the easy way out pulling mpeg2ts from the STB w/hardware modification.

I still think thats the easiest/least involved/etc method. And contrary to what you said earlier, there's not much a provider can do to a setup like that, they cannot 'break' or whatever the STB (well, short of sending buggy firmware to everyone's box (oh wait, they're good at doing that already)).

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jbrooks

Discussion Starter · #11 · Jan 17, 2007

how do you do scheduled recordings and channel changing ? With an IR blaster ?

Which STB do you use, and is it a customer owned STB ?

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timecop

· #12 · Jan 18, 2007

Yes on both counts though usually I just leave the set tuned into whatever channel I need recorded. I can't really go into detail regarding the modification as this isn't the place for it (the receiver has enabled 1394 output).

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