Quality Issues - Hardware vs Software Encoding

[mike1961]

Hello - a while back there was someone who posted that the quality with their Hauppauge 150 looks really good but only the one without the IR and looked not nearly as good with the IR. Then I got to thinking maybe it is not the IR but rather the older card obviously has software and not hardware encoding. So, I started wondering just how good the quality is with software encoding. I would think that given the same algorithms in hardware and the quality should be identical (but are they they same algorithms and so long as the hardware does not generate any type of interference). But if that is the case, why do some cards like the Hauppauge PVR 500 record much worse than say the NVidia. I'm not sure if it's the software algorithms (in hardware) that they use or other things. Either way, I'm wondering how it compares to software encoding.

Does anyone know? I know this much - clearly hardware encoding takes all the load off the CPU but with dual processors and CPUs running so fast these days, I wonder if it's OK to have such a load on the server? Also, if I tried this, will Sage know to use hardware encodiing for those cards in the server that have it and software encoding for those that don't?

One advantage of software encoding is that one may encode in either mpeg2 or DivX (but the processor load will be even higher).

I don't want to burden my CPU on my file server but I'm wondering if it's worth a test? Any thoughts on all this?

Thanks,
Mike

[Opus4]

Originally Posted by mike1961

a while back there was someone who posted that the quality with their Hauppauge 150 looks really good but only the one without the IR and looked not nearly as good with the IR. Then I got to thinking maybe it is not the IR but rather the older card obviously has software and not hardware encoding.

Just so you know: there is no older version of the Hauppauge PVR-150 that had software encoding instead of hardware encoding.

- Andy

[stanger89]

Originally Posted by mike1961

But if that is the case, why do some cards like the Hauppauge PVR 500 record much worse than say the NVidia. I'm not sure if it's the software algorithms (in hardware) that they use or other things.

Encoding quality is a function of a few things, including, time, horsepower, memory, etc. Starting from the beginning, the reason why hardware encoders are better than software for PVR (asside from the CPU usage issues) is that for live recording, time is a hard constraint. So hardware encoders, being ASICs, are optomized for encoding video live, in real time, where as software encoders (though less so than before) are less so (ie dropped frames when they get interrupted).

Now, while the codec may be the same, the encoder plays a very large role in the quality of the final encoding. So, given that the DualTV contains a newer, more powerful encoder, with (I think) more memory, it is able to do a much more thorough job making that final MPEG video.

Oh, and one more thing, many people are using analog cable for the comparisions, and with this, the quality of the tuner comes into play.

Either way, I'm wondering how it compares to software encoding.

It all depends on application, if you can remove the time constraint, software encoding wins every time, it can take as much time as it needs to do the best job possible. It can analyze the whole video to find out how best to encode it (two-pass VBR encoding). If something snags system resources it's no problem, the encoder just picks up where it left off.

If you're living in a realtime environment, like a PVR, it's a different story. First off, the encoder (software or hardware) doesn't have the luxury of scanning the whole file, all encoding must be single pass. But the real kicker is that in a realtime environment if the encoding gets interrupted, it can't pick up where it left off, because those frames are no longer there, new frames have arrived, hence you can end up with dropped frames, out of sync audio, etc.

One advantage of software encoding is that one may encode in either mpeg2 or DivX (but the processor load will be even higher).

The problem is DivX is far more difficult to encode than MPEG-2, and it's real strength (high quality at low bitrates) requires two pass encoding, the results of DivX with time-constrained single pass encoding are not significantly better than MPEG-2, just ask anyone who played with the Plextor.

I don't want to burden my CPU on my file server but I'm wondering if it's worth a test? Any thoughts on all this?

I don't really think so, my 250 (or 500, can't remember which I'm actually using at the moment), encodes pretty much transparently to my Dish Network source.

[Kirby]

Originally Posted by stanger89

It all depends on application, if you can remove the time constraint, software encoding wins every time, it can take as much time as it needs to do the best job possible. It can analyze the whole video to find out how best to encode it (two-pass VBR encoding). If something snags system resources it's no problem, the encoder just picks up where it left off.

Hence the one encoding app (I forget which) that has a preset for quality setting called "Insane" or something to that effect!

[stanger89]

You thinking of lame with it's -alt_preset_insane mode?

[mike1961]

Originally Posted by Opus4

Just so you know: there is no older version of the Hauppauge PVR-150 that had software encoding instead of hardware encoding.

- Andy

Andy - I stand corrected - I purchased the Hauppauge Go Plus which has an IR but does software encoding.

Thanks,
Mike

[mike1961]

Originally Posted by stanger89

But the real kicker is that in a realtime environment if the encoding gets interrupted, it can't pick up where it left off, because those frames are no longer there, new frames have arrived, hence you can end up with dropped frames, out of sync audio, etc.

Right - but that may not be a problem with a dual processor. There are a few factors I'm looking at. I'll first have to test and see how the signal looks with a cable (thus bypassing Sage). If software encoding does improve quality then I can always have one card that encodes in software and set the encoder merit and have my other cards hardware encode to keep the burden off my dual processor in the server. I can then easily see how much CPU time is taken up when recording a test show. Other things I'm working on and have discovered:

First, the wife keeps complaining about quality (especially on the 40" TV but not quite as much on the 27" since I got the nvidia dual tuner). The good news is that sometimes she said the guide was blurred and now I'm starting to think maybe she needs glasses. I keep trying to make believers out of my wife and kids. To them, everything is Sage's fault (even when weather.com does not report the right weather). I jokingly say when it rains or my kids have a bad day, it must be Sage. Always blame the software (if you are a software developer like me, you know how that goes). But, on a positive note, they do like all the features such as a central storage system and all the video archives.

Second - I'm thinking about running a "real test" by just plugging in a direct cable from the cable box to the TV (thus bypassing mpeg 2 encoding) and see how that quality looks. For me, I find most channels are just fine but a few look fuzzy from time to time so I think that is the signal (but it could be the signal plus mpeg 2 encoding contributing to the lack of clarity).

Third - She says the colors bleed (especially the reds). So that I can attribute to simply adjusting the TV color settings and saturation.

Finally, along with all the other benefits Sage has to offer, I love having only one small AOpen shuttle computer. It has replaced over 7 devices which is a huge space saver including: cable box, PVR, DVD, Playstation, Stereo receiver, tape deck, CD.

One quality my wife has is that she is unbelievably "visual." When she sees photos she can immediately detect when things are "off center" etc. So, I'm doing everything I can to improve the quality.

Thanks,
Mike

[camus]

Mike,
Do the "real test" you might be surprised, and make sure you show the wife.

I spent about a week tweaking recording quality and playback settings and found myself seeing quality issues no matter what I tried. I then just plugged directly to the TV and realized there is little difference, most of the issues with PQ had to do with me staring at the screen and over analysing.

[mike1961]

Originally Posted by camus

Mike,
Do the "real test" you might be surprised, and make sure you show the wife.

I spent about a week tweaking recording quality and playback settings and found myself seeing quality issues no matter what I tried. I then just plugged directly to the TV and realized there is little difference, most of the issues with PQ had to do with me staring at the screen and over analysing.

I'm not quite following you here? Are you saying, if I bypass Sage and just plug the cable directly to the TV (from the cable box) then the quality may be the same? I wish it were that simple but I don't think it is. I am anxious to try this but it's going to take a little bit of work. I'll first have to move the 40" TV downstairs since running a svideo cable or coax cable over 100 feet all the way upstairs may sacrifice quality. It may be easier to just get another TV for downstairs since we are going to replace that anyways.

She always goes back to "we never had these quality problems with Tivo." But, that was on the 27" TV and it's true that before I got my nvidia card, the quality was not nearly as good as Tivo. Now, for almost all stations it is comparable to Tivo with the 27". Regarding the 40", I think part of the problem is the colors (for her) are too strong. Since all TV's have there own settings (as well as the computer) for brightness, contrast, colors, and hue one can easily adjust these to make any picture look really bad or look great if everythiing else is right. So that is one factor but that won't fix the slightly "out of focus" / blurry channels that occur every so often.

Sometimes when we are watching TV and there is no question that it looks a little "out of focus" especially on the 40". Whether it's due to the mpeg encoding vs. direct from the cable box to the TV, software encoding or just the DirecTV standard signal (not an HD signal of course) is yet to be discovered. But, I can assure you there is no "over analyzing" here. Some channels come in really good while others also do sometimes but not always. So again, it could be a combination of things.

I think the problem these days with HD is most cards just won't accept them. Does anyone know if tuner cards will create a better mpeg file with HD than a standard signal (even though the cards are not HD)? I'm thinking that if a standard signal is less than the card's capability of 720x480 then the card might still create a better picture with an HD signal (even though the final mpeg won't be full HD).

Mike

[Kirby]

Originally Posted by stanger89

You thinking of lame with it's -alt_preset_insane mode?

No wasnt Lame, cant really remember.

[BobPhoenix]

Originally Posted by Kirby

No wasnt Lame, cant really remember.

I saw it in the DIVX encoder that came with DIVX create bundle with DIVX 6 if I remember correctly.

BobP.

Actually it is in the Codec Properties for Divx Pro see graphic:

[camus]

Mike,

In my post I was just saying that for me, I spent a lot time trying to get better PQ for SD than is probably possible, I have direct TV too and SD does look different on the HDTV set than it did on a SDTV set, I am assuming your 40" is HD? Anyway on the HD set the SD signal is being scaled up no matter what you do. For me, I was banging my head against the wall trying to get the recorded video to look better, finally after banging my head against the wall I plugged the directv box straight to the TV and realized it wasn't that much better, so it really wasn't the encoding it was the original signal. You can't make gold out of lead. As far as different channels, yes some will have a better signal than others, and this is definately more noticable on a HD set, this of course applies to a SD signal.

Now on the second part of you post. I am not sure what you are saying here. If you mean taking an HD signal and encoding it SD? If so, I am guessing here, it would because you have a better signal to begin with.

[mike1961]

Originally Posted by camus

In my post I was just saying that for me, I spent a lot time trying to get better PQ for SD than is probably possible, I have direct TV too and SD does look different on the HDTV set than it did on a SDTV set, I am assuming your 40" is HD? Anyway on the HD set the SD signal is being scaled up no matter what you do.

I totally agree with you on that. But, that would not explain why Tivo looks better on the 27" than my Hauppauge 500 looked. But, that's old stuff because like I say, now things look better with my nvidia card. It almost doesn't make sense to me that on a 27" TV with a tube, the video will look better than on say a 27" LCD (which is HD of course). I understand that the higher quality monitors "make everything stand out" but you would think there would be a way to make it look at least as good as a low quality TV tube. I'm thinking maybe the technology of LCD can just make things look more "pixelated" than a TV tube..[/QUOTE]

Originally Posted by camus

Now on the second part of you post. I am not sure what you are saying here. If you mean taking an HD signal and encoding it SD? If so, I am guessing here, it would because you have a better signal to begin with.

That is exactly what I'm saying but it is a question. In other words, if I get HD and the plug it into my tuner cards, then since my tuner cards are 720x480 (which I'm thinking is better than SD since I think SD is something like 352x240 or maybe 480x480) then I'm thinking even though the tuner cards downscale the HD, the end result will look better. Is this true?

The real problem I'm having which is keeping me from doing this right now (assuming it's true) is I don't want to mess with IR and the HD boxes from DTV don't allow one to change the channel via serial.

Mike

[camus]

Well, you may already know this but I just want to make sure your clear on it, unless the channel is actually HD you are getting the same signal from the HD satellite box as you would be from your current box.

Also, I have read that the Nvidia card is jump up from the 500 so that is good confirmation, as to why, couldn't answer that, but it is good to know.

[sniper's_scope]

new hardware always looks better than old hardware, that's the price of progress...