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TiVo Hacks

Which TiVo Is the Right One for You?
(Or, so you want to hack a TiVo...)

by Raffi Krikorian, author of TiVo Hacks

You're ready to throw out those clunky VHS tapes; you're ready to hear that satisfying "be boop, be boop" sounds when you hit the fast-forward button on your TiVo; you're ready to have TV your way. And you're ready to spend the two hundred dollars burning a hole in your pocket, so the million dollar question is, "Which TiVo should you buy?"

Everybody's situation is a little different, and thankfully, there is more than one choice of TiVo box to buy to complement your television set. The first thing you have to decide is which of the two TiVo "series" you want: the original Series 1 TiVo, or the newer Series 2 TiVo. On the surface they look the same, with the same menus and the same PVR functionality, but underneath, they are very different. The Series 1 has an IBM PowerPC CPU under its hood, whereas its younger brother has a more powerful MIPS processor. And it doesn't stop there--most of the hardware in the Series 2, from its MPEG encoder/decoder to its memory, has been upgraded. The most obvious change from the end user's persepctive is that the Series 2 TiVos now have USB ports on the back, adding functionality as well as the possibility of upgrading (maybe one day you'll be able to plug in your iPod and take TV with you on the road).

Another choice you have when deciding which TiVo is right for you is whether to buy the stand-alone TiVo or the DirecTiVo. Well, actually, this choice is mostly made for you depending on how you receive your television. Stand-alone TiVos plug into an analog television cable and the TiVo itself tunes to the right channel if all the channels are on that line. TiVo can also control most popular set-top cable boxes (whether it be for cable or satellite television) via an IR transmitter or a serial cable. Here, the TiVo will just record from channel 3 or channel 4, relying on the cable box to tune the channel. The DirecTiVo, on the other hand, has the DirecTV tuning circuitry already built into it--all you have to do is wire your mini-satellite dish directly into your DirecTiVo and it will do everything for you. You don't even need the DirecTV cable box.

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These two axes lead us to the four different choices available for TiVos: the Series 1 Stand-alone (SA), the S1 DirecTiVo, the Series 2 SA, and the S2 DirecTiVo. Each has its own set of pros and cons, and each fits a different niche of TiVo user. Do you have DirecTV or standard cable? Do you want to record two things at the same time? Do you want to play MP3s on your TiVo? Do you have a phone line or just a data connection? And most importantly, do you want to hack your TiVo?

In the rest of this article, I will strive to answer these questions for each of the four TiVo choices available.

Series 1 Stand-Alone TiVo

The Series 1 Stand-Alone was the first TiVo sold in stores. If you were one of the first in line in the late 1990s to buy one, you probably got your hands on one of the original 14-hour boxes from Phillips. Later on these became the 40-hours boxes that were also sold by Sony. The claim to fame these boxes' hold is that the majority of the original TiVo hacking was done on them. This is the box to which hackers figured out how to add more hard drive space; this is the box on which the first Tcl code for TiVo was authored; and this is the box on which the hardware was first intimately examined to see what it could do.

As mentioned earlier in the article, the Series 1 SA gets its television signal from regular coax--it will do all its tuning for you. If you are using a cable box, this TiVo has a port for an infrared transmitter that you can position in front of your cable box allowing TiVo to send it remote control codes. If you're lucky enough to have a cable box with a serial port connection, then you can probably make use of the TiVo's serial port (unlike the DB9 type of connector that most PC users are familiar with, the TiVo's serial port has only three connectors--for transmit, receive, and ground--so they get away with compressing it down to what looks like a 1/8-inch headphone jack) to wire them directly together.

As a last piece of hardware trivia, the Series 1 SA has a phone jack on the back so that the TiVo can dial into TiVo, Inc., allowing it to find out what television show is on at a given time and on what channel (one common misconception is that those "video advertisements" that appear on your TiVo also come in over the data connection--but that's not true. TiVo, Inc. leases time late at night on certain television channels and then asks your TiVo to record those channels to get its extra video advertisements). The TiVo's modem, in its original state, is this series's only method of networking.

The Series 1 SA is the most hackable one out there. Running the TiVoWeb is not a problem on this platform and performing video extraction is a breeze. In fact, if you wanted to start poking around and programming the box, this would be the platform to start with, as a lot of people have documented the event subsystem and the IO controls for the hardware. The one downside is that if you want a fast connection to your PVR, you will probably need to purchase and install a TurboNET or an AirNET to get it on your home network; this requires you to pop open the case and physically install a daughterboard onto your TiVo's motherboard. (In fact, if you don't have a phone line in your house and you only have a cable modem or a DSL connection, then you're going to have to install a network card into this breed of TiVo so that it may "dial home".)

I recommend this platform if you want to dive into TiVo hacking for the first time.

Series 1 DirecTiVo

Now this is the one for the sophisticated user. The DirecTiVo plugs directly into the satellite dish you have mounted on your roof. Instead of receiving an analog signal, the DirecTiVo receives the digital signal straight from the satellite. When a television show is recorded on the stand-alone TiVo, the TiVo needs to perform the analog-to-digital conversion to compress the stream for recording onto the hard drive. The DirecTiVo, on the other hand, records the satellite stream directly to the hard drive and then only needs to do a digital-to-analog conversion when playing back the video on your TV.

A second big plus to the DirecTiVo is its ability to record two television shows simultaneously (something most stand-alone TiVo users would kill to get). What this means is that you can either record two shows at the same time when you are not home, or you could watch live television while recording something else. SA TiVo users don't have this option; when their TiVo is recording something, they can watch only what is being recorded, or watch another recorded program; they do not have the ability to watch another channel all together.

So, why not get the DirecTiVo? It all comes down to how you get television delivered to your house. If you are like me, a television addict, then you have more than three devices with television access (TiVos, televisions, MythTV boxes, etc.), so DirecTiVo can get pricey quite quickly as you have to get tuning boxes for each individual component. With analog cable you can simply buy some low-noise splitters and wire up your entire house with cable. However, from a hacking perspective, most hacks that work on the stand-alone will work just fine on this breed of TiVo, though you may just have to jump through some hoops to get TiVoWeb working with dual-tuning capabilities.

All in all, the only reason to not get a S1 DirecTiVo, if you already have DirecTV (and are contemplating buying a Series 1), is if you are planning to move somewhere that does not have a plan to have DirecTV access in the near future.

Series 2 Stand-Alone TiVo

The Series 2 is the recent improvement on the original TiVo. It has USB ports on its rear so that peripherals may be added to the box. The most common use of a USB port on the S2 is to enable users to bring a high-speed connection with a simple USB ethernet adapter instead of having to poke around their PVR's internals as they would have to on a Series 1. The S2 SA TiVo also seems to be getting most of TiVo, Inc.'s software attention. The latest operating system, TiVo OS 4.x, has the optional Home Media Option, which allows you to play back MP3s or view images stored on your home network, as well as the ability to move television shows between two Series 2 boxes on the same network.

Unfortunately (or fortunately depending how you look at it), the Series 2 is also where TiVo hacking gets interesting. In an effort to appease the television and movie industry, TiVo, Inc. has attempted to "lock down" this TiVo from most hacking, most notably from video extraction. What TiVo, Inc. has done is create an operating system verification scheme that, upon boot up, makes sure that your TiVo has not been tampered with (that includes you going into your TiVo and modifying its configuration files, or putting any third-party software on board). Also, the S2 TiVo now encrypts the video that it records before it hits the hard drive, which means that even if you did get to the hard drive itself, you wouldn't be able to do anything with the recorded television programs since they are scrambled.

However, state-of-the-art hacking has recently been focused on getting around these restrictions. At first, the Series 2 had been the domain of hardware hackers who endeavored to replace the chip that was enforcing the security. More recently, people have borrowed from an academic idea called the "Two Kernel Monte"--or the ability to "hot swap" your Linux kernel without having to reboot your machine--to exploit bugs in previous versions of the TiVo OS on the Series 2. Using these bugs, clever people are able to get the S2 SA TiVo to boot into the most recent operating system with the security checks disabled. As for the video encryption, other people have discovered a work around on the encryption by "poking" (akin to peek and poke from the Commodore 64) into the Linux kernel's memory to ask the Linux kernel not to encrypt the videos. They then modify the main TiVo software so that it does not attempt to decrypt videos. With these two modifications, it's a breeze to get mplayer to stream videos, or use mfs_ftp to just simply ftp the MPEG's off your TiVo.

There is still a lot of unexplored ground for hacking on the Series 2 TiVo. People have not yet figured out the best way to do everything they can already do on the Series 1. If you are an adventurous type and want to get involved with helping the TiVo hacking community, or just want to stay on the bleeding edge, then this is the TiVo for you.

Series 2 DirecTiVo

There is great potential for this box, however as of this writing, it doesn't seem that OS 4.x has made it to the Series 2 DirecTiVos. This means that the S2 DirecTiVos don't have the ability to use the Home Media Option. However, this also means that getting inside this TiVo shouldn't be that hard! The hardware protection will still be there (but you can get around that in the same way that you do on the Series 2 Stand-alone), but there shouldn't be any hardware protection and you should be able to extract videos in the clear.

The choice here is a bit of a toss up. Eventually, there might be a Home Media Option for the Series 2 allowing you to play back MP3s, watch videos, and move around television shows, but right now there isn't. If you don't care about all that jazz, and you have DirecTV, then snag this box. But if you want to play with the latest and greatest, then maybe grab yourself a Series 2 Stand-alone and wire your DirecTV receiver box into it. You'll lose the ability to record two shows at the same time, but you'll gain other functionality in the process.

All this is ignoring the fact that there are a bunch of other TiVo devices on the market these days, like Pioneer's new TiVo with DVD burner. These haven't been around long enough for people to start experimenting with them, but who knows what these will bring to the table as they become more popular.


What all this boils down to is this question: What do you plan to do with your TiVo? A few months ago, if somebody wanted a TiVo to hack, the immediate answer was to tell him or her to grab a Series 1 Stand-alone. However, the Series 2 Stand-alone is becoming more hackable as more and more people play with it and explore what it can do. I waver, therefore, between recommending a Series 1 Stand-alone versus a Series 2 Stand-alone; the Series 2 is faster, and it's clear that, given some time, more and more of the TiVo hacking community will figure out the Series 2. If you want instant gratification and want to be able to do all the hacks you can right now to the box, grab a Series 1 Stand-alone. If you want to be on the bleeding edge, work on some TiVo hacking, and contribute something back to the community, grab a Series 2 Stand-alone; you can help test out other people's hacks, and do some hacking of your own.

O'Reilly & Associates recently released (August 2003) TiVo Hacks.

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