Software encoding vs. real-time MPEG-2 quality

[postul8or]

I've got a WinTV card where the hardware can only capture raw encodes as there is no internal hardware compression. As long as I can get the raw data to the hard drive I can always compress it later, quite often if I do a multi-pass, use a filter or something the compression will take a lot longer than the time of the movie.

While software doesn't have to be real time to do the compression, a hardware chip must do it real time. My question is, does the hardware take shortcuts on quality to make it real time? Hardware wouldn't really have an opportunity to do a multi-pass either so I assume CBR is more what would be used.

I see the benefit of the capture device creating the MPEG-2 file from the beginning, a lot less screwing around. Is a quality compromise the cost of this convenience?

[lordsmurf]

Huh?

Anyway, a hardware encoder is like having dedicated, proprietary software on the chipset of the card.

All you need is a good card. An ATI AIW card is not pure hardware (or even pure software), but it does great and puts out nice quality MPEG. A Hauppauge PVR card (or others) are hardware, also doing quite nicely.

The benefits of MPEG capture is less steps.

[BogieV]

I've had same dilemma.
With nowdays powerfull PCs even software encoding to MPEG2 in real time is not a problem (exept rised case and CPU temps).
What's bugging me is that capturing you can never fit the file size to DVD apropriiately!
I'm using Leadtek TV/capture card and for decent quality 2hr movie at 6000kbps usually the file is at 5-6GB range. I have to reencode the MPEG2 which is not so good after all.

[lordsmurf]

Calculate your bitrate better. Easy as that.

[BogieV]

Yeah, I should do that
It's OK when you know the movie's lenght!

[lordsmurf]

If it's unknown, go lower, as low as you can while staying in acceptable limits. There is no rule that says you must fill every kb of the disc. Just use it for storage, whatever the file size.

[dh]

My experience shows that the MPEG2 quality as captured by DVD Recorder is better than that by hardware card.

[postul8or]

Huh?

Anyway, a hardware encoder is like having dedicated, proprietary software on the chipset of the card.

All you need is a good card. An ATI AIW card is not pure hardware (or even pure software), but it does great and puts out nice quality MPEG. A Hauppauge PVR card (or others) are hardware, also doing quite nicely.

The benefits of MPEG capture is less steps.

Yeah but real-time means CBR basically, or perhaps a bit of a guess for a VBR (would be a 1 stage VBR). The question is, how much worse is the quality compared to software encoding that you can customize just a little more. 2 or 3 pass VBR can be a fairly large benefit for high motion scenes in movies.

[OmegaSupreme]

Hollywood movies use hardware compressors. They look pretty nice.

[Jester700]

My experience shows that the MPEG2 quality as captured by DVD Recorder is better than that by hardware card.

That's an interesting generalization, since different chips are used in different gear of both types. Conversely, IIRC the *same* Conexant chip was used in certain set tops as well as some cards.

Maybe YOUR DVD recorder beats YOUR card, but in that case, it would be helpful to know what those pieces of gear were.

[BogieV]

I'm sure software encoding VBR 2 pass will be better quality.
What we are discussing here is REAL time capture.
Skipping the extra steps I don't care if the quality is lower as long as I can save 5 hours of busy PC conversions, plus huge amounts of HD space in the first place.

[Nelson37]

The advantages of real-time Mpeg-2 encoding are obvious, as with many things in life, it's all a matter of "compared to what?".

My own tests indicate that an AVI 720x480 cap of digital cable movie encoded with 4-pass VBR in CCE, using AVISYNTH for IVTC, will in fact yield a better-looking encode and/or a smaller file size. However, the difference is marginal, and there are many issues - time, HD space, dropped frames, etc.

However, using MMC real-time Mpeg-2 with a slightly higher bitrate, narrow-range VBR, and real-time IVTC (for uninterrupted movies only), yields results that are very, very close if not indistinguishable, with no dropped frame issues and much more storage availability. Faster CPU is a significant factor in quality.

Real-time seems to benefit more from cleaner signal, or to do worse with noisy signal, depending on how you look at it.

Note the ATI card is "hardware-assisted", sort of a hybrid. As CPU speeds increase, a dedicated encoder will IMO become less necessary.

[vhelp]

But there's another problem that I see w/ calculating the proper bitrate
for when you are capturing TV programs. Commericlas.
.
Commercials can add anywhere's from 2 to 4 minutes, pending upon the
show, and who's buying the space/air-time.

So, where's this effecting our HD/PVR capturing (and quality) ??
The answer is simple.

* 1st, the bitrate is being calculated based on length.
* 2nd, a bitrate is set (based on above calc)
* 3rd, because of the 1st/2nd, the final MPEG is not what it could have
.. been, because (ie, given a 1 hour tv program) if our calc derived a bitrate
.. of say, 6000 for one hour tv program, you are shortchanging yourself
.. because end in the end, you will not be keeping the commericals.
.. On average, a one hour tv program is 40 to 45 minutes long (minus the
.. cut tv commercials) In order to fit a given project onto a CD, you had
.. to use a given (though smaller) bitrate that was based on a one hour projection.
.. Because of this, your final MPEG-2 were bitrate starved, and suffered in the
.. end, its quality. That 6000 bitrate could have been 7000, (but based on a 45 min
.. capture, though minus the commercials)
.. Unfortunately, you can't capture w/out the commerical in a one hour tv program.
.. .
.. However, you can.., you just have to do TWO things:
.. A) - recalculate, but this time, based on the true timeline, (ie, 45 minutes)
.. ---- but make sure that tv program is going to be 45 minutes (maybe its 40)
.. .
.. B) - STOP capturing when the commercials air. Then, you're good to go


My thoughts ...

I'm still hesitant on the Hardware MPEG-2 capturing though. I still think that
even they are cutting corners, though to a lesser degree. At least in the low
budget gadgets, they are probably practicing this. We are talking about consumer
toys here.
.
IMO, I don't think that anything hardware (in the consumer market) will ever be
able to replace (if not contend with) software encoders. TMPG is a very touch
act to follow. I've used a (so called) commerical product, (ie, CCE) and I have
to say, TMPG (IMO) beets this app (when I'm using TMPG) maybe not by a lot, but
imo, enough to make me stick w/ TMPG straight through. The only thing negative
about TMPG is it's speed. It's pretty slow. But, quality is what I'm after,
and the main objective. Speed is secondary. Always should be. Else you are
asking for corners to be cut. I rather wait longer (some cases, much longer)
if the results are to be worth it, quality'wise. But, theres another side to
TMPG (as is others) you have to be "skillful" in it. Otherwise, it will fall
in the same catagory as all the others you have tried.

Hardware encoders have their place
.
The less noise in your source, the better your results. That means, if your
source is noisey, and/or has macro-blocks in them, your chances lesser, in
terms of quality. VHS is not really noisey. I think that we are all misslead
into believing this. But, I won't get into it here (It's not the place)
But, you can obtain a good MPEG-2 if your setup is good, and there are no
"added" noise into the chain of events (ie, wires; length; unit being captured)
Many more things to factor here.
.
Another thing to worry about, is IVTC. I have yet to see a hardware encoder
provide this built-in. This is a major blow in the quality department, because
quality would be raise considerably (my theory)
.
Sometimes, quality is not a concern, and a hardware will probably beet a
softare real-time, in terms of quality, depending on the source (ie, Interlace
vs. Telecine)
I haven't tested this. Its more of a theory. Again, you have to know your
product well.. (Be skillful in it)
Most important, you have to be honest with yourself. If quality is your main
concern, be honest !!

The above is my 2 cents worth.

-vhelp

[mpack]

Note the ATI card is "hardware-assisted", sort of a hybrid. As CPU speeds increase, a dedicated encoder will IMO become less necessary.

Maybe not. The biggest overhead for full MPEG2 compression is the motion estimation step, ie. where you search for the best match for the current macroblock within a certain search range on a previous or future frame. The overhead of this function is proportional to the square of the search radius. So, your CPU speed would have to square also if you want to seriously bite into this overhead. Realtime software can speed this process up by restricting the search radius (a problem if the motion is fast), or by only outputing I frames (in which case there is no motion compensation step), or by using hardware which can do a lot of searches in parallel. There are faster software algorithms for motion search, but the ones that are really faster all sacrifice quality.

[snafu099]

I agree with what VHELP has written almost completly.

I have two usb hardware capture devices and 1 software capture card in use, in the same system.

Consumer/home use only. "I" con't see any quality differance from my hardware captures from quality of commerical dvd and I can still use my pc as normal (not including disk read/write intensive stuff) while doing the captuire since there is very low cpu usage.

IMHO, for the average consumer, like me, with limited time, skill, budget, attention span, tec, etc but still with a desire to achieve from tv, vhs or other source for personal/family use, a good hardware encoder will provide all the quality they want/need.

Having said that, If the intended output is not intended to be disc playable in settop player, then a hardware encoder may not be the right choise as most only encode to mpg 1 or 2.

[postul8or]

For me I have found my WinTV in XP just doesn't work right. It always wants to capture at 320X240, and yes I might be able to kick it in the butt with new drivers and get it working, so this discussion has been valuable to me (I'm convinced to look for a hardware encoder).

Would the Hauppage 250 be a good card, or are there cards that produce comparable MPEG-2 quality for cheaper, or better quality for the same price.

Any posts or articles that will give me this info?

[lordsmurf]

Yes, the Hauppauge PVR 250 and 350 cards are two of many good MPEG2 card. ATI AIW is my favorite, and Matrox and Canopus have some too. Even AVerMedia supposedly threw in a few MPEG2 cards recently, and I believe ADS has some external ones as well. The choices have increased greatly this year.

[GKar]

I had a lot of fun capturing MPEG2 Hardware VBR with my Dazzle DVCII, it was definitely a time saver when coupled with TmpGenc Author and decent quality too. Definitley go with one of the aforementioned MPEG2 Hardware cards.

Here's a current sale for the Hauppauge WinTV-PVR-250 with Remote for $79.99:

http://www.compusa.com/products/product_info.asp?&ref=cj&pfp=cj&product_code=310591

[junkmalle]

I Hauppauge WinTV-PVR-250 with Remote for $79.99:

http://www.compusa.com/products/product_info.asp?&ref=cj&pfp=cj&product_code=310591

Wow, that's a good deal!

[postul8or]

Too bad I didn't see deals like that in Canada...

[disturbed1]

Hollywood movies use hardware compressors. They look pretty nice.

Their hardware compressors use 2-3x pass VBR after it's passed through a $60,000+ DVSN preprocessing machine.

Not to mention the source materials they use can not compare to anything we would capture from a TV broadcast or a simple sub $2,000 consumer camera.

Given a good clean source, most hardware based mpeg cards do a decent job. If your a purest, or the source is far from perfect, nothing beats a lossless (or lossy) avi capture, filter, then multipass software encode.

If the file isn't that bad off, I usually use the S-Video output on my DC30 (after editing) or the TV out on my Matrox card, to play back to my DVCII for real time mpeg capture. No the results are not as good as a software encode, but it gets done in a quarter of the time, and it's hard to notice the difference on my TV.

[fmctm1sw]

This is a classic thread with good points on both sides. Reminds me of the old "Could VBR ever be as good as CBR?" thread tossed around a couple years back here...

[SatStorm]

For fast results, a DVD standalone recorder is a wise choice.
For good results, an entry hardware mpeg 2 capture card is fine (ATI included, especially for the NTSC users).
For better results, you go the classic root: Analogue capture to avi, encode vbr way to mpeg 2.

A great alternative, is any card with realtime software mpeg 2 encoding (using mainconcept 1.4.2 that is). The results is like ATI's realtime mpeg 2 (and some time better). IMO, the PAL users have to consider this alternative as a good one, when they capture from TV, or DVB channels.

[greymalkin]

this is indeed an informative post and it seems as though you can get a quality product by being either rich or creative .

disturbed made a good point that is true for ANY media whether it be image, audio, or video...a big part of your finished products quality is how good/clean your source is.

i personally don't care for the stand-alone dvd recorder units becuase they don't offer the flexibility that the editing software does. I do usually capture straight to mpeg2 because working with avi's kills my pc (even though it's a P4 3ghz!!). back to the stand alone's however, it may just be my ignorance, but I tried to help a friend with their dvd recorder unit that was basically dubbing from a VHS source but it would only record @ 704 by 480. This obviously caused undesirable effects...

i'm sure i initially had a point but i've lost it now....

[gshelley61]

i personally don't care for the stand-alone dvd recorder units becuase they don't offer the flexibility that the editing software does. I do usually capture straight to mpeg2 because working with avi's kills my pc (even though it's a P4 3ghz!!). back to the stand alone's however, it may just be my ignorance, but I tried to help a friend with their dvd recorder unit that was basically dubbing from a VHS source but it would only record @ 704 by 480. This obviously caused undesirable effects...

i'm sure i initially had a point but i've lost it now....

What undesirable effects fom capturing VHS at full D1 res are you referring to? It works fine for me...

And as far as editing MPEG2 captured with a DVD recorder... no problem. Womble MPEG Video Wizard and MPEG-VCR are both very good and very fast frame-accurate MPEG2 editors that do not re-encode (no quality loss). I author and burn the final DVD on the computer, too. However, I've pretty much quit capturing to my PC altogether. The DVD recorder does a better job, IMHO. There are never any audio/video sync issues, no dropped frames, and the audio is AC3 to start with!

[Capmaster]

this is indeed an informative post and it seems as though you can get a quality product by being either rich or creative .

disturbed made a good point that is true for ANY media whether it be image, audio, or video...a big part of your finished products quality is how good/clean your source is.

i personally don't care for the stand-alone dvd recorder units becuase they don't offer the flexibility that the editing software does. I do usually capture straight to mpeg2 because working with avi's kills my pc (even though it's a P4 3ghz!!). back to the stand alone's however, it may just be my ignorance, but I tried to help a friend with their dvd recorder unit that was basically dubbing from a VHS source but it would only record @ 704 by 480. This obviously caused undesirable effects...

i'm sure i initially had a point but i've lost it now....

You should be getting the best results at that res. Preferable to 1/2D1 (352x480) IMO

[vhelp]

@ snafu099

IMHO, for the average consumer, like me, with limited time, skill, budget, attention span, tec, etc but still with a desire to achieve from tv, vhs or other source for personal/family use, a good hardware encoder will provide all the quality they want/need.

I have to agree with you here ..thanks to my experience with the DVD Xpress
unit.

I also agree with the part about having a clean source. That is so true too.
DV cams are a great example. Assuming outside footage. The only other *main*
problem with DV is that it is pure Interlace. Every frame. But, couple the DV
home footage with a good Tripod and experience camera operated man, and you have
a great receipt for next-to Cinema quality, even from Hardware MPEG-2 devices.
.
I hope to run some tests based on that statement I just made, with some footage of
my own and my DVD Xpress unit. But until then, just take our (my) word for
it

-vhelp

[greymalkin]

I initially captured from vhs @ 720x480 when I first got my card but it always looks worse than capturing @ 352x480. I always figured this is because you are basically "blowing up" a low res source. Apparently you are saying I should still capture @ 720x480????

I would understand that if my source was 720x480...and for some good sources it might still look fine, but i have noticed that recording tv/vhs @ 352x480 has given me a product very veery close to the original whereas trying to capture at higher resolutions (and yes I increase the bitrate..up to 8000 even) introduces anomalies.

[lordsmurf]

I initially captured from vhs @ 720x480 when I first got my card but it always looks worse than capturing @ 352x480. I always figured this is because you are basically "blowing up" a low res source. Apparently you are saying I should still capture @ 720x480????

I would understand that if my source was 720x480...and for some good sources it might still look fine, but i have noticed that recording tv/vhs @ 352x480 has given me a product very veery close to the original whereas trying to capture at higher resolutions (and yes I increase the bitrate..up to 8000 even) introduces anomalies.

If it looks good, leave it alone.
This kind of hi vs mid res depends on many factors.

[disturbed1]

I initially captured from vhs @ 720x480 when I first got my card but it always looks worse than capturing @ 352x480. I always figured this is because you are basically "blowing up" a low res source. Apparently you are saying I should still capture @ 720x480????

I would understand that if my source was 720x480...and for some good sources it might still look fine, but i have noticed that recording tv/vhs @ 352x480 has given me a product very veery close to the original whereas trying to capture at higher resolutions (and yes I increase the bitrate..up to 8000 even) introduces anomalies.

This depends very much on the capture card itself. Some capture cards have very poor scalers at certain resolutions. There is a long thread in this forum, and also at www.doom9.org about the BT 8x8 cards, and the problems their scalers have at certain resolutions. There's also some info comparing the results with other cards that use different scalers. Philips is another popular scaler on capture cards, but has it's impurities at different resolution as well.

If 720x480 looks crappy, try 704x480, and then 640x480. If it looks fine at 640x480 use avisynth (or similuar) to rescale to the desired sized for post production. Some cards produce the optimal image quality at odd ball resolutions (576x384), it just depends purely on your hardware and capture codec.