Recording question

[Ivomir]

Hi.

I was watching a live show on my S3 and decided to record it, 17 minutes into it.

If I do the same on my S2 unit (still running the 7.3.1 software) it would 1) record only from the current show, and 2) the recording would start no more than 30 minutes ago. So in this case it would use 17 minutes from the live buffer and keep recording from there. That has been my experience for the many years I've used Tivo before.

On the other hand the S3 recording included more than 1 hour of previous programming (1:17 to be exact), and included 2 other shows prior the current one.

Why is it doing it? I'm not saying it is a bad thing, just trying to figure out the system behind it. The manual was no help.

Obviously the S3 buffers more than 1 hour of live TV, even if it doesn't let me rewind more than 30 min. How much is it, and how does the S3 decide how much of it to include in the new recording?

One more thing. When I start a new recording the status bar on the S2 would be initially as long as the show's duration. On the S3 in the case above it started as long as the current recording (1:17), and kept growing (or actually the time scale was shrinking) as the recording progressed (up to 2:00 when the show ended).

My S2 has problems upgrading to 8.1, so I don't know if what I'm describing is an 8.1 thing, or an S3 thing.

Please help me understand.
Ivo

[btwyx]

This is similar to the way DirecTiVos work. I'd guess its to do with direct recording of the digital signal. With the S2, the TiVo knows exactly what the bitrate of the compressed data stream is, as the TiVo is doing the compression. So it can have a buffer which is exactly big enough to hold exactly half an hour.

For digital signal, the TiVo records exactly the signal that's sent to it. The TiVo has no control over the bit rate its recording, it has to cope with whatever its sent. The siganl could be anything between approx 0.5 - 2 GB per hour for SD, or 5-9GB per hour for HD. So the TiVo has to have a buffer which is large enough to fit half an hour of the highest rate signal. In that it may be able to fit 9 hours or more of an SD.

It only allows it to seem like there's a 30 min buffer, but in reality there maybe more space. Whenever a recording is requested from live, the entire buffer, or maybe a number of whole file system blocks are dumped to the recording, and you can get more than half an hour before the request.

The green bar is a bit messed up when recording like this. That could be considered a bug.

[Ivomir]

For digital signal, the TiVo records exactly the signal that's sent to it. The TiVo has no control over the bit rate its recording, it has to cope with whatever its sent. The siganl could be anything between approx 0.5 - 2 GB per hour for SD, or 5-9GB per hour for HD. So the TiVo has to have a buffer which is large enough to fit half an hour of the highest rate signal. In that it may be able to fit 9 hours or more of an SD.
Thanks, that sounds plausible. :)

While I wouldn't call this a bug, it is definitely quirky, since it is unpredictable. I'm not sure what would be a good way to implement it. Maybe depending on the current position of the play cursor it can detect which of the shows still in the buffer I want to record. If the beginning of the show is not in the visible 30 min buffer it would extract as much as possible from the full buffer, without including any previous shows.

Anyway, this is certainly better than the S2. The S2 would refuse to record the portion of the previous show that is still in the buffer, if the next one has already started in real-time. Instead, pressing the record button would start recording the new show, and will purge the old one from the buffer.

The green bar is a bit messed up when recording like this. That could be considered a bug.
Yeah, this is a bug. I would expect the status bar to include the full show and the green bar to display the current progress. The software has all the information to size up the bars properly.

[astrohip]

Talk about strange timing, I just came to this forum late at night to post about weird buffer timing, decided to catch up on threads before I posted mine, and saw this one. My story...

I'm watching King Kong, from the start. The movie is at the 1:20 point, and due to a couple of munchie breaks, I'm watching around the 1 hour mark. Decide it's too long to watch, hit record. Notice when the green bar comes up, it shows green all the way back to 0:00. No way, I say. Start jumping around in the recording, and sure enough, it has captured the entire 1:20 of movie. What a buffer! :confused:

[MScottC]

My question would be, are these shows with ultra large buffers SD or HD? I'm thinking perhaps the buffer reaches a fixed (or close to it) size. An SD stream in that buffer will obviously be much longer than an HD stream. Just thinking here.

Scott

[aaronwt]

I can't say I've ever had more than 30 minutes show up in the buffer on any of my TiVos. What happens though is that it will sometimes include the whole 30 minute buffer when it shouldn't. Lets say there is 30 minutes in the buffer and I hit the record button 15 minutes in an hourl long show. Suddenly the recording thinks the show started 30 minutes prior instead of 15. I've never tested it to see if it actually records the whole show or only part of it when it reaches what it thinkks is the hour mark. whenever it happens I always go into the recording and tell it to record longer to make sure I get the entire program. But in 5+ years I've never had a buffer more than 30 minutes show up.

[Ivomir]

I did another experiment this morning at 9:22. One of the tuners was on NBC (in SD) the whole night and was currently showing some news show from 9:00 to 10:00. Before that there was another news show from 8:00 to 9:00. I hit record, and the recording started with 45 minutes already complete. That means it includes 23 minutes of the previous show that is 1 hour long.

I just can't make sense out of it... Tivo's primary function is recording, and I'm feeling it should do a better job at making predictable recordings.

Ivo

[astrohip]

But in 5+ years I've never had a buffer more than 30 minutes show up.

Me too. Until the S3. I have now had two separate instances where I hit record while watching a show and the recording (hence the buffer) went back more than 30 minutes. As an experienced TiVo user, I know exactly what I am seeing, so there is no doubt it happens. As it doesn't happen consistently, it leads one to assume that the buffer is not time-based, but worst case scenario size based (as someone above mentioned).

One of the few tweaks I've always wondered why TiVo hasn't offered by now is a larger buffer, since in essence it's "free". Or at least a variable buffer. And of course, the ubiquitous FSI. :D