Channel Lineup affect quality?

snoopy · #1 08-30-2005, 12:05 AM

Can the choice (analog cable vs digital cable) affect quality of recording. I am all but certain it has in my case. My cable company says I have analog cable but then if I choose digital cable in the lineup, my quality seems to improve dramtically. Is this supposed to be the case?

bluenote · #2 09-10-2005, 02:35 PM

We're talking about regular old hauppage cards here right?

The lineup is actually something abstract in comparison to the *fact* of analog or digital cable, you can think of it in terms of being just a label. (So no, it should not affect anything. However, there are more things in your philosophy than I have dreamt of, so...)

However, if you think you're getting better PQ, maybe you are

Cory

snoopy · #3 09-10-2005, 03:17 PM

Quote:

Originally Posted by cnovak

We're talking about regular old hauppage cards here right?

The lineup is actually something abstract in comparison to the *fact* of analog or digital cable, you can think of it in terms of being just a label. (So no, it should not affect anything. However, there are more things in your philosophy than I have dreamt of, so...)

However, if you think you're getting better PQ, maybe you are

Cory

Yeah they are Hauppauge 500. I'm actually 'almost' sorry I got rid of my TiVo but I am still holding out hope for better STVs and more hard drive space once I can afford it. At this stage none of the STVs seem to have everything and HD space is a real bummer. Also it does not appear as though frey has any real intention of releasing Studio.

If I set SageTV to highest quality (the same the TiVo records at), the picture improves dramitically but it takes up about 6gigs per hour of video. DTV's TiVo takes up only one GB per hour! This six to one ratio is a killer! The only reason for this as far as I can theorize is DTVs decision to manipulate the standard mpg2 format to deviate from the spec in order to acheive the quality. Some DTV/TiVo users once thought that the change in the mpg2 format was DTVs attempt to keep TiVo users from burning DVDs which we can now do despite this change. As it turns out, that had nothing to do with it. What they were doing was changing the format of 'standard mpg2' to allow for better compression at the highest quality. The 'original' TiVos after all, had only 20gb hard drives for 20 hours of recording. Don't get me wrong here. I LOVE the THEORY behind SageTV and STUDIO and it has GREAT promise! The space vs quality issue though continues to be a big problem for me.

blade · #4 09-10-2005, 05:17 PM

Unless I read your post wrong, your comparing the capture of a digital satellite signal with a Tivo to capturing an analog cable signal with Sage. That alone is going to make a huge difference in quality. From what I've seen there is no comparison between Dish or DirecTV and analog cable.

I use 3.5 gb/hour which is a little overkill IMO. You definetly shouldn't need 6 gb/hour. If you're really pushed for space you might consider converting the mpeg2 files to divx. You can get them down to around 600-700mbs (maybe lower) without much loss in quality.

As cheap as HD's are though the easiest route is to just buy more space. I picked up a 200 gig drive for around $70 a couple of months ago. That's around 57 hrs of storage at 3.5 gigs/hour.

stanger89 · #5 09-10-2005, 06:35 PM

Quote:

Originally Posted by snoopy

If I set SageTV to highest quality (the same the TiVo records at), the picture improves dramitically but it takes up about 6gigs per hour of video. DTV's TiVo takes up only one GB per hour! This six to one ratio is a killer! The only reason for this as far as I can theorize is DTVs decision to manipulate the standard mpg2 format to deviate from the spec in order to acheive the quality. Some DTV/TiVo users once thought that the change in the mpg2 format was DTVs attempt to keep TiVo users from burning DVDs which we can now do despite this change. As it turns out, that had nothing to do with it. What they were doing was changing the format of 'standard mpg2' to allow for better compression at the highest quality. The 'original' TiVos after all, had only 20gb hard drives for 20 hours of recording. Don't get me wrong here. I LOVE the THEORY behind SageTV and STUDIO and it has GREAT promise! The space vs quality issue though continues to be a big problem for me.

Lots of confusion in this post:

1) DTivos don't work like a PVR 500, DTivos just archive the bistream that DTV broadcasts. The reason they look good is because it's an EXACT copy of what was broadcast. Further DTV has multi-thousand dollar (I'm guessing) video encoders, and access to pristine source material. As such they can get away with broadcasting (and therefore recording) at about 1.5-2Mbps and still have it look good. Compare that to the maybe $20 CX2341x with limited RAM available, and you'll see the difference.

2) Last I heard DTV didn't use standard MPEG-2, I've heard it referred to as MPEG 1.5, but regardless it's not the same. This is the reason that R5000 can't record SD channels, and last I heard, it required processing to get files retrieved off a DTivo to a useable format (conversely, Dish broadcasts in standard MPEG-2).

3) I'm guessing you've never actually used a standard Tivo, because while they advertise the 20GB units as 20Hr recording, and it is possible, it looks like CRAP. In reality you can only get about 5-7 hours of good quality recording on such a unit. Basically standalone Tivos have recording quality and space usage equivalent to the Conexant CX2341x used in the PVR cards.

-summary

There is no way* that a PC is ever come close to matching a DTivo, Dish PVR, cable DVR for both quality and time/GB, because those devices have a huge advantage in that they don't need to encode the stream, they just archive the broadcast. You can record at the same bitrate, but the quality will be worse, or you can record at (essentially) the same quality, but the size will be larger.

*If/when MCE gets cablecard, and hopefully satellite smartcard support, then a PC will be able to match, exactly, the provider provided PVRs/DVRs exactly.

-question

Not sure I understand the HD space problem, one of the benefits of using a PC vs a STB is the essentially unlimited, user upgradeable hard drive. If you don't have enough, get a bigger one, HDDs are cheap after all.

snoopy · #6 09-11-2005, 04:24 AM

Thanks guys for the response. I'll set 3.5gb per hour and see how that goes.

blade · #7 09-11-2005, 04:33 AM

Actually I'm using a custom bitrate, 3.2 gb is the closest default one in Sage.

bluenote · #8 09-14-2005, 03:31 AM

Snoop,

Maybe your video woes are due to your playback? When using software playback, there is MUCH variability due to how you configure your deinterlacing, what filters you use etc. I don't know much about this because I do not use software playback. (ie: through video card). Maybe someone can back me up here or tell me I'm wrong -- a default "all things being equal" sage install using video card playback without any tweaking will look like crap. (don't jump on me if this isn't true, it's just my impression and its based on very little empirical data -- CRT playback for about a week).

That aside, I record at 1gb/hr (which isnt quite good enough for some movies, and if Im going to archive something I turn it up, but I find that this is the best space/performance tradeoff for regular TV viewing on a small (by today's standards) television. However, I did modify my recording qualities to make a custom one for myself, and I know that it could be tweaked further. In a nutshell the main change I made was to take one of the lower data rates and make it VBR.. and I believe I turned down the audio bitrate. I found this to be far superior to the regular "Fair" setting which I found intolerable.

I feel your pain on the diskspace issue. I have around 800gb+ of storage devoted to video and it's still not enough -- in fact I just noticed Im down to 4gb so its time to do some housekeeping again (sigh).

Stanger was just educating me in another thread and it sounds like you can get your Sage to do MPEG-4 which could give you a 50% reduction in file size for similar output quality or possibly even a larger reduction (in theory, 70% should be possible, but don't count on it). That may be the way you need to go, although personally I have decided to wait a bit and see how things mature because this is a relatively new development in the sage area.

In the end, YMMV, I know a lot of people here absolutely require high bit rates but I find on my TV and with my viewing habits, and with my relatively undiscriminating eye, I can live with low bitrates. Personally I like hardware playback (PVR-350) and so do a lot of other people.

Anyways, to summarize:

1) somehow eliminate your decoding/playback as the source of the problem (it could be aggravating a low bitrate into unwatchability) -- maybe someone more educated on this than me can jump in for you, if not there are many posts about tuning PQ in a software environment-- Im not really sure how you could determine whether this is part of your problem or not though (sorry).

2) Experiment with your recording settings in the sage.properties file, at least for me it was worthwhile to make the effort and tune this a bit.

3) Investigate MPEG-4 and the Plextor TV402U (?) not sure about the model there, for lower file sizes. Note that I have not decided on this route as yet myself, even though I am gagging for a lower filesize, so best to look for some opiniions from people that have one (I'm not sure if Stanger has one or not but he knows quite a bit about them for one)

4) (just thought of this one) make sure your cable signal is clear. a bad signal will eat up file size with very little quality very easily. I believe that this can be on the edge of noticeable visually but can have a noticeable effect once compressed.

Hope some of this helps snoop
Oh, and do come back and tell us how you've made out and what you've decided, we're all in this together and we all like to hear the stories good or bad of the challenges people have gone through.

Cory

snoopy · #9 09-14-2005, 03:52 AM

Cory thanks for that. I'm not sure how I would fine tune? I am fairly comfortable with it now that I jumped the setting up to DVD Standard Play at 3.2gb per hour. I would prefer a bit better quality at that setting but that is actually darn good. It just takes up 3-4 times more space than my TiVo did which is less than desireable. I'm not sure what bitrate settings to change?

What would you recommend from here if I do not want to go down in quality at all?

bluenote · #10 09-14-2005, 04:21 AM

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