choosing a record quality? PVR-350

[bluenote]

I've just gotten my PVR-350, and SageTV working pretty much perfectly. I gotta say, quite a learning curve, considering I do this kind of thing for a living.

Anyways, I've got to thank everyone for all the answers I've been able to find in these forums and so forth ... it seemed that every issue I came across had been dealt with here previously and it saved me a lot of time.

The last thing I'm trying to figure out is what recording quality to use!

I've been playing the old "record, play, change quality, record, play" and the "live tv, switch to cable, switch to pvr ... can you see the difference? I can't see the difference..."

My problem is ... it seems like the PQ *varies* not so much on the basis of recording quality / data rate but by the *show*.

For example -- I've got American chopper episodes recorded at SVCD quality, and "Fair" and I can *barely* see the difference between SVCD and DVD LP (for example).

Yet, I take something like Stargate, or Buffy, and sometimes I begin to see compression artifacts (the 'double image', as well as the mpeg "repeating squares") but it seems like the size of the file does NOT equal quality.

Live TV comparisons vs. the default RQ don't seem to add up for me either. I haven't quite done enough comparisons to know though.

Note: I am using the TV-OUT on the 350 ... previously when I didn't have the local play turned off, I got a lot more of (what I think were) poor interlacing and generally crappy PQ which I guess was due to my default s/w decoder.

Can anyone help? I have a lot of disk, but I want to write this stuff to DVD so I'm hoping to keep episodes smaller if I can.

I'd almost say that a darker show needs a higher data rate, vs. something like American Chopper which has a lot of bright contrasting images. ?? Am I imagining this?

thanks for any thoughts

Cory

[stanger89]

Originally Posted by cnovakMy problem is ... it seems like the PQ *varies* not so much on the basis of recording quality / data rate but by the *show*.

For example -- I've got American chopper episodes recorded at SVCD quality, and "Fair" and I can *barely* see the difference between SVCD and DVD LP (for example).[/QUOTE

That's to be expected. Overall higher recording rates will give you better picture. You could, for example, record everything at MPEG Max Quality (5.6GB/hour) and everything would probably look great, but as you've noted, that's a waste of space.

Yet, I take something like Stargate, or Buffy, and sometimes I begin to see compression artifacts (the 'double image', as well as the mpeg "repeating squares") but it seems like the size of the file does NOT equal quality.

That's to be expected. Overall higher recording rates will give you better picture. All things being equal higher rates will give you better quality, to a point. There's that point at which going higher doesn't gain you much or anything. What is it that affects where that point is? The amount of change in the video, or more simply, the amount of action/movement. Stuff thats stands still is easy to compress, so things like Chopper, where there's not a lot of movement will work well at lower rates (except for maybe sparks). Stuff like Stargate, with a lot of action/movement are harder to compress, and the encoder "runs out of bits" sooner on those.

Live TV comparisons vs. the default RQ don't seem to add up for me either. I haven't quite done enough comparisons to know though.

That's because there is no true, live TV, when you watch LiveTV you are watching a recording, just like any other time, except you are watching it as it's being recorded. And the LiveTV recording uses the default recording quality.

[bluenote]

Hi Stanger, thanks for the reply.

I realize that "live tv" is always delayed recorded, what I meant to say was changing the default RQ and going to live tv, and then changing the RQ again.

It sounds like there is two solutions, if I've got this correct:

1) use a high data rate and be done with it, even if you're wasting a lot of disk in some cases

2) set your bit rate per favourite.

Stanger, care to comment on what your default data rate is? Or do you set per show? What do people find as the best tradeoff point generally?

Also -- are all the rates available by default in Sage Mpeg2 or Mpeg1 ? I couldn't accidently stop hardware encoding (which is preferred and seems to do a better job from my limited experience) by picking the "wrong" setting, could I?

thanks

Cory

[korben_dallas]

I'll give my two cents, since as a new Sage user, I've had similar issues.

My purchase of the Sage/Plextor/Streamzap bundle left me broke, for this month. So I don't have the cables yet for connecting to my TV, thus I've been watching everything on my flat panel. It's a Samsung w/ 12ms response, so I haven't had to worry about ghosting. I've played around with "Best", "DivX Theater Highest", and "MPEG2 Max". The "best" setting really does show flaws. The "DivX Theater Highest" was signifcantly better, but I could see artifacts on Futurama.. perhaps cartoons are difficult to compress? "MPEG2 Max" is what I've been using for the last two weeks, and unless I'm sitting right in front of my FP, it is great. I would say the occasional block or frame rate drop while watching Stargate (my favorite show) is forgiveable considering how much better of a picture my FP gives me over my old TV. Plus, the sound is way better too. I never realized how crappy the RF demodulator must be in my old TV until now. That said, as soon as I get paid again, I'm going to buy the rest of the cables needed to hookup video and audio into my TV, and then I can do a better comparison of the different quality settings. And I haven't even tried MPEG4 yet.

It's not really fair to compare your videos on a monitor or flat panel to videos on your TV. The TV can only show 720x480 vs a flat panel 1280x1024 and a monitor at 1600x1200 (or higher). You may end up being fine with a lower recording setting quality simply because of the resolution limitation of your TV.

[mls]

The source can also effect how good the encoding works. Older shows are often from video tape. These can have extra snow or grainyness that can cause problems with the encoding. Live broadcasts direct from the TV station will normally encode much cleaner.

Then there are newer shows or movies that often start from a digital source (such as DVD). Since these were already encoding in an MPEG format, then converted to analog for broadcast, when you encode them you may get extra doubling up of the artifacts that occured in the original decoding to analog.

And, then there are the network feeds themselves. Most of these are now digital. Depending on their original source, along with the conversion to digital for transmission via statelite, and down conversion back to analog... well, there's any number of other artifacts that can confuse your encoder.

In other words, there's not real exact answer for which recording quailty does the best job. It depends on the source signal, amount of action, and your own personal preference. Some people don't notice certain artifacts, while to other they are annoying.

If you're output is to a standard definition TV you may not notice hardly any difference between the quality settings simply because a SDTV is only capable of reproducing lower quality. The differences would be far more noticable when output to a monitor or an HDTV though.

So, you're kind of stuck with trial and error in deciding which setting is good enough for you. On my end, I output (via S-video) to a cheap 20" SDTV. I use the Extra Long Play DVD setting and that produces a quality very close to what the TV displays directly from it's own tuner. Of course, my cable tv service isn't all that good to start with either. If you're outputting to a better display device you may want to use a higher quality setting than I do.

On last thing, before even messing with the recording quailty settings you may want to get either the Avia or Digital Video Essentials DVD's to get your display set up properly. Be sure to use the same decoder when using those to adjust things that you plan to use for other playback in SageTV. Then check the manual or the FAQ's section for how to make Color Correction adjustmenst for each of your encoding cards.

Once you have that all set up correctly, then back to trial and error with picking a recording quality that pleases you best.

[stanger89]

Originally Posted by korben_dallas

The "DivX Theater Highest" was signifcantly better, but I could see artifacts on Futurama.. perhaps cartoons are difficult to compress?

Actually you're absolutely right about that, while I see often that animated stuff is easy to compress since it contains large blocks of uniform color (normally easy to compress), in my experience it's not the case. Video compression does more than just compress frames (I frames), it predicts future frames (P frames IIRC), and sometimes past frames (B frames? not sure). The thing about animation is that instead of smooth (relatively) transitions from frame to frame, the picture tends to "jump" and that wreaks havoc with the motion vectors used to predict the P and B frames.

[bluenote]

Thanks for all the suggestions guys! I'm looking into getting that AVIA so I can make sure everything is calibrated right.

for what it's worth, I thought I'd share my subsequent experience --

I created a new set of the "fair, good, great" data rate configurations, making them VBR, with the base data rate the same, and the peak being about +100000 or 1500000 . In this config, I found that I got files that were the same size as my previous "fair" recordings, however the quality got a lot more consistent. *now* it seems like I can properly increase the data rate and have a bit more of a consistent expectation for the shows that I am looking at.

I haven't really done enough viewing yet to be certain, but on my regular TV this really made the difference, before, the quality was really really variable going from decent to HORRIBLE in some scene changes and so forth. I'm just watching some commercials now (with water and such.. previously the exact same commercial made the compression artifacts VERY obvious) and it's a LOT better.

I don't know if that's worthwhile to know, but I thought I'd try and contribute back. thanks again guys

Cory

[mls]

The Avia DVD covers most of the basics very well. However, the Digital Video Essentials DVD does provide a lot more detailed information. I bought both, but pick which ever you feel is best for your situation and pocket book.

For VBR to work really well, it needs to be able to look quite aways ahead to compare frames to. When they make movie DVD's, their systems can look ahead in the film frames and therefor do a much better job.

Unfortunately, our hardware encoders can't buffer enough ahead for the encoder to make really good decisions in real time. Because of this, you should be able to get even better quality by using CBR instead. However, that does make larger file sizes also, so one has to decide what trade off one is willing to make (smaller files or better quality).

Oh, if you do get Avia or DVE, be sure you use the same decoder in SageTV for DVD playback as you plan to also use later for playback of Sage's own recordings. Different decoders produce different video levels, so if you set things up for one and then use a different one later things will not be calibrated correctly to match that decoder.

Good luck

[stanger89]

Yeah, I'd go DVE over Avia as well.