series 3 HD horsepower and recording rate...

[tiver]

Ok, let's say hypothetically that tivo enables MRV on the s3.

And let's say that I successfully set up TivoServer on my unix fileserver so that I can watch my .ts/mpeg/.avi/divx movie collection through the tivo.

Now, I have some 1920x1080x60fps videos ... and although those are rare, I have a _lot_ of 720p @ 30fps videos, and certainly lots of 1080i, etc.

My own experience shows me that a 3.06ghz p4 has drops a lot of frames with a 1080p .ts file.

So the first question is, how strong is the s3 tivo, and what is the maximum density of, say, an mpeg transport stream (resolution+fps) that I could send to it over TivoServer ?

--------

Now, a somewhat unrelated second question - we all know the s3 tivo has "30 hours" of HD capacity. However, some HD channels are 720p, some are 1080i, some are even 480p, etc. - and all of these saved shows should take up different numbers of bits/second on the drive.

My assumption is that the "30 hours" figure is for 1080i, which I believe is the max res the tivo can save, and that if I save a lot of 720p or 480p, I will actually get more than 30 hours.

Is this assumption correct ?

Thanks.

[mr_zorg]

I don't actually have a S3 unit and so I can't answer any of these questions from actual ownership experience. However, comparing a TiVo to a 3Ghz P4 isn't a fair comparison. The TiVo is a specialized computer that is designed specifically for video playback. It has dedicated MPEG decoding hardware that the typical PC lacks and I'd hazard a guess the Linux OS it runs has been tweaked to provide better support for real-time operations. Most desktop OSes just aren't geared for that. I don't believe the S3 handles 1080p at all, since that's not a broadcast standard. The specs for it only say "standard modes including 1080i & 720p widescreen". If it works at all, it will probably work just fine (for the reasons mentioned previously).

Now, I realize I haven't technically answered your question, but maybe this is helpful somehow.

[tiver]

Yes, I certainly understand that it's not a good comparison - general purpose processor vs. purpose-built decodinng system.

I was just putting the anecdote about the p4 in to make it clear _why_ I was askig the question. Knowing that decoding HD mpeg streams is not "easy"...

Ok, so you think I can feed it 1080i though, since it can play 1080i in its own format ... I'd like some better confirmation though, since a 1080i tivo-saved recording vs. a TivoServer-served 1080i .ts may _also_ be comparing apples and oranges...anyone have a comment ?

--------

And the second question - do I get 30 hours of 1080i, and if I am saving 720p or 480p I get _more_ than 30 hours ?

Thanks.

[Jamie]

Yes, I certainly understand that it's not a good comparison - general purpose processor vs. purpose-built decodinng system.

I was just putting the anecdote about the p4 in to make it clear _why_ I was askig the question. Knowing that decoding HD mpeg streams is not "easy"...

Ok, so you think I can feed it 1080i though, since it can play 1080i in its own format ... I'd like some better confirmation though, since a 1080i tivo-saved recording vs. a TivoServer-served 1080i .ts may _also_ be comparing apples and oranges...anyone have a comment ?

It's hard to know without trying it, and the pieces aren't available to try it just yet (if ever). My guess would be that as long as you don't exceed the ATSC OTA bitrates,19.28Mb/s, you'll be fine. MRV doesn't really "stream", it stores it to disk, but lets you playback while the transfer is in progress. It's possible the network won't be able to keep up (although 100mbps is fast enough for several HD streams). In that case, you'll just have to start your recordings transfering a bit before you start watching.

And the second question - do I get 30 hours of 1080i, and if I am saving 720p or 480p I get _more_ than 30 hours ?

The capacity depends entirely on the bitrate your signal provider is using. In my experience, 1080i OTA from our PBS affiliate uses ~ 7.5GB/hour. They've allocated part of their channel bandwidth to a digital rebroadcast of their normal SD stream. I haven't looked at the size of 780p recordings, but I would expect them to be similar (1280x760x60 is pretty close to 1920x1080x30).

On the network affiliates, I get a lot of 480i upconverted to 1080i by the station, and that seems to use the full 1080i bandwidth and space. :-(

[RavenStL]

Its all in the compression. IMO

I would guess the TIVO just stores what it gets, so the 1080I or 720P or whatever really is just a guess, it comes down to bit rate.

Just look at Dtv, they compress (and re-encode I guess) 1080I to what, 1280x1080i not 1920x1080i. So DTV HD will take up less then the original signal, say from an OTA source.

Dropping the bit rate reduces quality, but increases storage space.

Million Dollar question: At what "bit rate" or amount of compression of an HD signal is "too much". When do you "lose" HD. Tough call, I love ATSC but it seems Dtv Lite is so/so in comparison.

[tiver]

hmmm...

I thought that was all a moot point with s3/HD tivi - in another thread I was assured that tivo (when working with digital signals) just dumps the bits it gets on the line to the disk.

That is to say, that with a digi signal, there is no tivo-introduced-compression - WY(get_on_the_wire)IWYG. That is why I was then compelled to ask about the "30 hour" figure, because clearly some signals down the (HD) wire take up more space than others...

[Jamie]

hmmm...

I thought that was all a moot point with s3/HD tivi - in another thread I was assured that tivo (when working with digital signals) just dumps the bits it gets on the line to the disk.

That is to say, that with a digi signal, there is no tivo-introduced-compression - WY(get_on_the_wire)IWYG. That is why I was then compelled to ask about the "30 hour" figure, because clearly some signals down the (HD) wire take up more space than others...

You've got it right. The question is, how much compression is your signal provider doing? DTV is compressed, it's just compressed by the signal provider before they send it to you.

[dcormode]

Yes, I certainly understand that it's not a good comparison - general purpose processor vs. purpose-built decodinng system.

I was just putting the anecdote about the p4 in to make it clear _why_ I was askig the question. Knowing that decoding HD mpeg streams is not "easy"...

Ok, so you think I can feed it 1080i though, since it can play 1080i in its own format ... I'd like some better confirmation though, since a 1080i tivo-saved recording vs. a TivoServer-served 1080i .ts may _also_ be comparing apples and oranges...anyone have a comment ?

--------

And the second question - do I get 30 hours of 1080i, and if I am saving 720p or 480p I get _more_ than 30 hours ?

Thanks.

The Tivo can decode and display MPEG2 files on the fly without dropping frames. Decoding divx files requires much more horsepower, the Tivo doesn't have it nor the software.

The tivoserver, the desktop software that shoots avi files to a tivo decodes the avi then re-encodes it as MPEG2 on the fly. For SD file a 3ghz processor is required to do this in real time, slower processors will work, but you can start watching the show right away. IMHO for a divx that is truly HD a much faster processor will be require for real time.


The digital broadcast standard is about 8.5 GB / hour for any transmission. This will be shared by all the streams on a channel. So a 1080i or 720p or even 480i DTV signal may be anywhere between 2 and 8 GB/hr. The local affiliate or the network will decide this. All of these are sent in MPEG2 format.

... so you may well get no more recording time with a 480i DTV broadcast than a 1080i.

I've noticed frequently 1080i scenes in CSI Miami on CBS where the action moves quickly enough that the MPEG pixelation becomes noticeable. I almost never see that on SD DTV since each pixel has 6x the bandwidth compared to 1080i.

[drez]

Sorry to threadjack... but Tivoserver does not need 3GHz for realtime.

The most-current tivoserver available at sourceforge (v0.4.4-a4 May 11, 2006) is known to be significantly slower transcoding because of a bad ffmpeg build. BTU fixed the issue with tivoserver-0.4.4-a4.2 (June 17, 2006) but he didn't put it at sourceforge.

I have a Celeron D 330 (2.6GHz) that can do 2.4x realtime (SD xvid .avi source) and a Athlon 64 3200+ that can do 3x realtime with tivoserver-0.4.4-a4.2 (June 17, 2006) and newer (like the unofficial tivoserver-0.4.4-a4.6 with wmv3 support (December 1, 2006).

Maybe it's time for version .5 ... the versioning is getting out of hand...


Reference:

Turns out that the ffmpeg CVS that is used in -a3 and -a4 is MUCH slower than that used in -a2. Not sure if it's a bug or what. I've relinked the current tivoserver to the ffmpeg from -a2.

I'm leaving on vacation in a few hours, so I don't have time to make a proper release, but for those who want, I'm hosting -a4.2... here's a link:
http://tuckscandy.com/share/tivoserv....2(cygwin).rar

p.s. not sure, but may require a newer cygwin1.dll

[Jamie]

The Tivo can decode and display MPEG2 files on the fly without dropping frames. Decoding divx files requires much more horsepower, the Tivo doesn't have it nor the software.

...

All true.

As it turns out, the Series3 does have a bcm7411, a realtime hw h.264 decoder. It's not clear at this point what it is being used for, if anything. I don't think any of the cable or OTA signals use it.

[chedlin]

My best guess about the TiVo's support for h.264 would be to allow it in future Internet video applications, and possibly for the future of cable carriers, even though it isn't used now.

[jt72]

Sorry, double post - see following message.

[jt72]

I just recently got the upgrade to 8.1.1-01-2-648 on my S3. In the "Program Details" page it displays how much harddrive space the show is taking up. Here are some results from some shows I have sitting on my S3.

1:00 480i fullscreen digital - 1.05GB (Discovery Science) (1.05GB/hr)
1:00 480i letterboxed digital - 1.12GB (Discovery Science) (1.12GB/hr)
1:00 480i letterboxed digital - 1.17GB (Discovery Science) (1.17GB/hr)

1:00 480i fullscreen analog - 2.42GB (USA Network) (2.42GB/hr)
1:00 480i fullscreen analog - 2.42GB (USA Network) (2.42GB/hr)

2:00 1080i (Movie: Serenity) - 10.44GB (HBOHD) (5.22GB/hr)
2:15 1080i (Movie: Die Hard) - 12.02GB (HBOHD) (5.34GB/hr)
1:15 1080i (Standup Comedy) - 7.56GB (HBOHD) (6.05GB/hr)

1:00 1080i (Documentary) - 7.44GB (Discovery HD) (7.44GB/hr)
1:00 1080i (Documentary) - 7.45GB (Discovery HD) (7.45GB/hr)

Given those quick few bits of data, I would say that the bitrate seems to vary depending on the signal type, channel, and in the case of HBOHD it seems to vary somewhat based on the content.

My best guess about the TiVo's support for h.264 would be to allow it in future Internet video applications, and possibly for the future of cable carriers, even though it isn't used now.

The message I got after the software update said that it would allow for delivery of content from the internet. I'm hoping this will include things like video-podcasts along with more options.

Gary

[tiver]

Gary,

Thanks - although I notice no stats for 1080p - is that not a resolution you get from any of your CATV sources ?

The tivo _will_ record 1080p, right ?

Given the sizes you show above, I wonder if anyone can make an educated guess as to how big 1:00 @ 1080p would be ?

[Jamie]

...
The tivo _will_ record 1080p, right ?
...

Nope.

Here's one discussion about it.