2004-06-11

PVR - Description and Ideas

First I bet a lot of you are going to ask: what is a PVR.

For those that already know about PVRs, and don't care to read my explanation, please skip down to the FreeVo section.

A PVR is a personal video records. Also known as DVR, digital video records. You may know about one of the more famous devices out there right now: Tivo.
But all this is a fancy way of saying the computer age's answer to the VCR.
Basically a PVR is a device that stores video on a hard drive.
Because the video is on a hard drive, and there is a computer involved in recording the video, there are some exciting things that can happen on a PVR.

1) A PVR will often have a Guide of the programs that are on, and available. This can make it easier to select a show to record. In some cases, the software is fancy enough that you can ask it to search through the guide of TV shows. Some will automatically change the recording time if a show's schedule is changed. Some PVR's will even let you tell it to record any show that matches certain criteria, such as your favorite actor.

2) A PVR can keep track of shows you have recorded, and can automatically erase older shows as it needs space. Of course you can also sat a show to be saved, so it won't be 'taped' over.

3) This is one of the biggest selling points of PVRs: they make it easy to skip commercials! They give you a quick skip button on the remote, the usually pops down 30 or 40 seconds in the show, and another that goes back about 10 seconds. Thus allowing you to get past commercials in about 5-15 seconds.

4) A PVR can playback a stream that it is currently recording, but at a differnt pace. Combining that idea with #3, and you get a popular pastime with PVRs: start recording a show, say at 8pm. But start watching it about 8:15pm, from the beginning. Skip the commercials, and you wind up finishing watching the show about the time the show ends, or shortly after.

5) A PVR can pause live TV, and even go back and replay a moment. Usually a PVR will cache (keep a copy) of the video of the show you are watching, back at least a few minutes. That means if you tuned into a show 5 minutes ago, but go a phone call, you can go back to where you tuned in to the show. Or if you were smart, you pressed pause when the call came in, and you can just go back to watching the show where you stopped it. Behind the scenes, the PVR is recording the show to the hard drive, but it is not saving it for replay at a future time. Some PVRs will let you convert a live stream that is cached (or paused) into a recorded event, to save for later playback.

There are different model PVRs out there. Tivo is the most popular. It has some of the best features. But it's hard drive options are a little small. But besides it's up-front cost, they get you with a monthly fee. You have to pay about $13 a month for Tivo: 'for the show guide'. But Tivo will also download software updates and install them without your knowledge or ability to change that. Tivo also uploads data about what you are watching. While Tivo says they only use this data for statistical purposes, and never identify personal viewing information, it is a bit concerning. Especially since you have to pay them $13s a month for the priveledge.

I suppose I shouldn't complain too much, though. I pay $5 a month for my PVR. It was a special with Dish network. It came with 100G hard drive, which comes out to about 100 hours of record time. But I don't have my unit plugged into the phone lines, and I don't believe they track 'statistical' viewing information. I will admit that the software in my PVR is not as nice as what I hear Tivo offers. It will not dynamically change programming based on the guide. It doesn't have any automatic programming features, like look for an actor.
I have also had some technical problems with the unit. Twice now, it has gone off into la-la-land, continuing to record a channel past the end of a show. And it would not allow any commands to stop recording. The only solution was to unplug the unit. And when I plugged the unit back in, all the hours it was recording wound up being in a lost file. In other words, I have lost about 15% of my recording time to files I can't access or delete. Dish's solution was for me to delete all the shows on the hard drive, and the space would come back. I have not gotten around to that, because there are some shows I would have to dub to tape, and I just haven't taken the time. I did delete some shows, and after a power-cycle, I got back some of the lost space.
There have been a few times, about 4 times in the last 2 months, where the unit shows the channel information, but will show no shows. This always requires unplugging the unit to get it to clear the problem. One time I had to play with the satallite settings to get it to re-sync. And this is furthur complicated by the fact that I have put the tuner in the basement. The hard drive noise could be a little distracting in our bedroom, and the coniditon lights could be annoying. The unit comes with a radio/IR remote. The radio portion controls the PVR, so putting it in the basement works pretty well. And the IR controls the TV, VCR and DVD player in the room.
In spite of the lesser software and glitches, I am still very pleased with the PVR. I love the higher quality of playback over video tapes, and the convieninces.

I was thinking about the technical details about PVRs. I know Tivo has special hardware (chips) to do view encoding and another for video decoding. This means that the Tivo doesn't need a very fast CPU at all.
I was wondering if I could record from a non-Dish source on my PVR. The it suddenly hit me: my Dish PVR doesn't need a video enocder chip. It is getting digitally encoded signal already from the satallite. Thus it can store the already encoded video directly to the hard drive, and only needs a decoder. It also means that it can't be used to record anything from a source besides the Dish.

It is interesting to note that most (if not all) of the PVRs on the market run a version of Linux. This includes both the Tivo and my Dish PVR. You wouldn't know it to look at the TV or at the outside of the units. But under the covers, that is exactally what it is running. This has even let to some people hack around with their PVRs. There are some sites to add larger hard drives to a Tivo (obviously voiding the warrenty).

FreeVo
Just a day or two ago, I read about making your own how brew PVR with Linux, using software called FreeVo. There is a related site for building your own hardware unit for FreeVo

3 comments:

Digichrome said...

Long time Tivo user here. :) Love my tivo. I have a PVR from our local cable company and its OK but it lacks the sophistication of our Tivo. I'm thrilled today as Tivo has announced much cheaper hardware and has cut the fee on the 2nd or more boxes (which can share programming).

Also of note is MythTV another free (I think) PVR option. One that's not free but very nice is called SnapStream. A nice site to check out is http://www.pvrblog.com.

Ok, I'm done hijacking this blog entry now :)

Keith said...

Thanks for your comments! I would hardly call adding some great info as hijacking :)

Keith said...
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