Bitrate, Compression, Size... All Means Squat... Why?

[Sektion8]

Hi Len0x (and everyone else) :),
Thanks a million for the prog, it's a dream-come-true compared to all the crap needed to do even one movie. I've been educating myself for the last few months on the whole scene, going from site to site & guide to guide... Each one conflicting with the other in settings/opinions, or grossly out of date (like 3years)... :( (only to make me wait another 5 days after sign-up before I can post here :(

I've got one "basic" question (that'll probably have a complex answer) I'd love to ask please... (I'll get there in two-sec)

After playing with AutoGK for a few months of solid testing/trial & error, I've got my settings looking like this to get the best results (for what I'm after - fitting multiple high-quality Xvid movies onto DVD):

Max horizontal res: 640
Audio: CBR MP3 128
Fixed size: 1540mb
Compression: XviD

Any higher res/audio results in nasty quality movie.
Trying to fit movies onto 700mb is a disaster.
I've picked that size because after chopping credits, I can fit 3 movies to a DVD in high quality (about 1500mb each). I'd give them about 9.5/10 - *very*-slight background colour-shifting/boxy issues with dark colours (not sure what this is called - only happens with DivX/Xvid video). The audio... Dunno, I figure constant quality is better than up & down quality.

My question ("finally!" everyone says):
* How does "everyone else" on the net get movies compressed to down to 700mb or even 1380mb with A1 quality...?

To word it differently:
* Why can others make a higher quality XviD movie at often half the bitrate I do?

As in, despite anything I do with any settings, I can only come close at double the size :(

When I replicate their settings, I get nasty quality :(

As mentioned, I've searched everywhere looking for the answer (someone will probably make me look stupid now), but nobody can agree on it... One guide will say that bitrate has to be be 1500kbits+, another guide will say that below 0.17 bit ratio will be nasty... Yet these vids I've seen prove all this to be false... :confused:

Here's an example of "their" settings:
Video...........: XviD
Video Bitrate.: 2 Pass VBR
Audio...........: MP3 @ 48000 Hz
Audio Bitrate.: VBR 128 kbps
Duration.......: 42 minutes
Resolution.....: 512x384
Frame Rate...: 29.97
Size.............: 375mb

PS. Sorry for the long post, I like to get all details down first time.

[CWR03]

Simple answer: it's not usually done with AutoGK. I use Gordian Knot which has far superior control, and I can easily match "their" settings and quality. I've gotten 13 episodes of Enterprise (over 9 hours of video) on one DVD-R, and they look fantastic. It's not a difficult learning curve.

I don't fully understand the VBR audio usage - it can cause synch problems, and the end file size is the same so there's no improvement in the video. A small improvement in video can be made by using 44.1 khz audio instead of 48 khz.

*Edit: We appreciate the time spent on details. It's becoming increasingly rare. :) See this post (http://forum.doom9.org/showthread.php?t=100868) for an example of the opposite extreme.

[zacoz]

@CWR03: Sounds like I shouldn't settle for AGK quality without spending some time trying out GK.

Oh well, I am on holidays, so now's a good a time as any.

[Guest]

Yet these vids I download prove all this to be false Please do not discuss downloaded content here per forum rule 6. Thank you. :readrule:

[Sektion8]

Please do not discuss downloaded content here per forum rule 6. Thank you. :readrule:

?? But it's not illegal content... :confused:

Either-way, I've edited the post, sorry for any confusion. :(

[Sektion8]

Simple answer: it's not usually done with AutoGK. I use Gordian Knot which has far superior control, and I can easily match "their" settings and quality.

Thanks for the quick answer! :thanks:

Hmm, I know what you mean, but don't understand - if that makes sense... I don't know "why is it so..."

Is it because it's all using general-style settings, a "one-size fits all" approach, or it's set to "general" speed/quality ratio (or something like that)...?

I've looked through advanced settings plenty of times, but couldn't find anything related to play with... Even while doing IceAge, I didn't want to choose Cartoon setting for fear of ruining-it... (Turns out 700mb & normal settings were perfect - the only one like it!)

Hmm, looks like I'm/We're (users) are at a crossroads and need to decide what our priorities are... As it would seem we can't have both :(

Dang, always the way...

We appreciate the time spent on details. It's becoming increasingly rare. :) See this post (http://forum.doom9.org/showthread.php?t=100868) for an example of the opposite extreme.

:) I'm new to this forum, but plent silly amounts of time at several others. It's frustrating to see the one-word answers going back & forth like tennis, when it all could've been put in the first post - makes it so much easier to help/read/understand when it's all there in one! :)

I'm happy with AGK, but know I should/could get up-to 6 movies per DVD, instead of the 3 that I'm currently getting. As you've done with TV shows, I'd like to do the same, as plenty of serials are split over piles of discs, when they would be 10x better on just one XviD disc... :)

Thanks again for your help... It would be good to know if that's it though, are we stuck with this quality/size/speed dilemma...? :confused:

[Guest]

?? But it's not illegal content... OK. Please note that in your posts in the future, because we assume the worst to protect the forum. Thank you.

[CWR03]

Is it because it's all using general-style settings, a "one-size fits all" approach, or it's set to "general" speed/quality ratio (or something like that)...?
Sort of...depending on the length of the movie and the aspect you choose, it's doubtful you'd ever get six movies on one DVD. I shoot for only two or three myself, but I try to keep the original width of 720 and use AC3 audio, which is bulky. AutoGK does a good job of deciding how to do a particular encode, but as I mentioned Gordian Knot allows more control over everything, even audio. I played with all the settings and did probably 300-400 small test-encodes to see what everything did, but I'm a stickler for quality. The Gordian Knot tutorial is very thorough (so I hear - I haven't read it).

[len0x]

To some extent comparison in the first post reminds me of apples vs oranges. Unless you're are sure that you are comparing encodes from absolutely the same source (if it is then R6 might be violated again) you can't do that. What you said about "their" settings looks pretty normal to me, but when translated to full movie length - its under 1:30h for 700Mb, which is quite rare for modern movies. And if you compare it to 2h movie you already lost 33% of quality. Also what looks like TV captures from HDTV has much more quality to start with comparing to DVD, so encodes with the same parameters would look really different as well.

P.S. I also would not overrate GK as the key for getting good quality encodes. I mean the only real advantage that can make huge difference is ability to use avisynth filters. But you have to know what to use and when. I'm pretty sure most GK users don't have enough knowledge for doing optimal encodes for every given source (I'm not even comparing the number to total video encoders "out there"). You just can't expect many ppl spending half a day finding the best encoding strategy for every movie. So just by using GK you won't automatically improve video quality.

[Sektion8]

OK. Please note that in your posts in the future, because we assume the worst to protect the forum. Thank you.

NP, I completely understand :)

I played with all the settings and did probably 300-400 small test-encodes to see what everything did, but I'm a stickler for quality.

Hmm, yeah... a stickler though & terms like "highest-quality" are all grey (oops, just narrowed my location :)) areas, as each person's opinion/balance/interpretation is the deciding factor - as numbers alone mean nothing.

I play all my movies in my HT setup, on a PJ - so there's instant loss there. I do what I can to help things, but there's always going to be things stopping perfection, even for the fact of using lossy codecs.

I'm not a videophile (?), no perfection-junky etc... Just appreciate good quality. I've seen them all, so I know the difference, but I'm not going to kill myself over a 0.138% letterbox-ratio mis-calc or something like that.

I use what I consider the the most important real-world test... Can anyone notice the difference... As in, If I/no-one else can notice the difference between an original and my backup, then why bust my balls any further over it... ?

In my eyes (years of "real-world" experience, but zero education on these things) I can't tell the difference - I'd really have to be looking for it to notice the diff between 640 vs. 720 when on the PJ.

BUT, as said... "numbers mean nothing", as the thread-title suggests... It's theory/rule I've almost/always followed with PCs (if not with everything).

"their" settings, much lower than mine, are much higher quality than mine...

[Sektion8]

To some extent comparison in the first post reminds me of apples vs oranges.

Yeah, but as just mentioned (in my small novel - sorry), it's real-world that's most important IMHO... What good is a difference on paper, if it can't be seen/appreciated on-screen. Video/film/signal can go through ten different transformations, but it's the end product that matters. To add to that, if "they" can make 512 tv look much better than 640 dvd... something's not right... That's why I'm here - I don't know why, and wish to learn please.

What you said about "their" settings looks pretty normal to me, but when translated to full movie length - its under 1:30h for 700Mb, which is quite rare for modern movies.

I agree, it is very common, but I couldn't replicate it to save my life! :(
I thought it was safe to assume they're not using a simple prog - and are going through the ringer of settings to get it so high - but thought I'd ask/learn why.

And if you compare it to 2h movie you already lost 33% of quality.

I agree, I've hardly seen a minute over 90 for 700mb high quality - As we probably all know, they're 1.38gb when getting over 90min.

Also what looks like TV captures from HDTV has much more quality to start with comparing to DVD, so encodes with the same parameters would look really different as well.

Hmm, yeah?! Is that because DVD is already using lossy compression? (correct?). Does HDTV use compression at all? To reply though, they're almost always SD.

P.S. .....

Hmm... How do you think these people pump-out this stuff so quick, so often then...? It's almost like live-encode sometimes, seriously! (using hardware instead?)

[Sektion8]

:thanks: First things first... I'd really like to thank you guys again for your help. Tutorials are great, and I know I need to read some more (honestly, don't feel rude pointing me to one), but they're only 1-dimensional - They don't answer back :)

There's tons of questions I've had, and would consider FAQ, but they're not covered in AGK. If you're open to suggestions, I'd love to suggest them.

....

The other (main) thing I cannot avoid, despite playing all-around (mentioned in OP) is this image issue, despite how high-quality I really go (within reason)... I'd claim a 9.5 to a 10/10 for my videos if it wasn't for this prob, it's the last niggling problem I can't shake for this quality/size ratio, and I'm trying to get size lower, not higher...

The image can be razor-sharp with excellent colours throughout... BUT... I get this issue (screenshot needed?) where in the background, (mainly darker colours) have blocky-issues, like it's ran-out of colours to blend-with. It's not like what used to happen with VCD that the processor couldn't keep up with, it's amongst like-colours, not going from black to white for example, but going from super-black to dark-black - it goes blocky/washy, and attracts the viewers attention instead of the foreground :(

[CWR03]

I get this issue (screenshot needed?) where in the background, (mainly darker colours) have blocky-issues, like it's ran-out of colours to blend-with.
This is, unfortunately, a drawback to MPEG-4 compression. It combines several compression methods, and one of them is "blocking" similar colors to reduce the amount of information needed to contain the picture. The lower the bitrate, the worse it gets. The two most effective ways to lessen this are with smaller resolution settings or a larger end file size.

[manono]

And it'll look worse if viewing on an LCD monitor than on a CRT.

[len0x]

Is that because DVD is already using lossy compression? (correct?). Does HDTV use compression at all? To reply though, they're almost always SD.


How do you know its SD? Final resolution doesn't tell you anything. HDTV is better because its resolution upto 3 times more than on DVDs, so you start with better quality and you end with better quality (and it doesn't matter if final resolution is SD).

[chilled]

I don't fully understand the VBR audio usage - it can cause synch problems, and the end file size is the same so there's no improvement in the video. A small improvement in video can be made by using 44.1 khz audio instead of 48 khz.

please explain this to me:

-why is video improved when using 44.1 instead of 48 khz? isnt the resulting mp3 exactly the same in size (but maybe worst in quality -the mp3 not the vid- if 48 used for low bitrate)

-inst it "commonly" stated that VBR at any average bitrate (and size) delivers better quality than its equivalent CBR bitrate ? where has the cbr < abr < vbr thing gone? were I wrong all this years? hope hell no :)

[CWR03]

-why is video improved when using 44.1 instead of 48 khz? isnt the resulting mp3 exactly the same in size (but maybe worst in quality -the mp3 not the vid- if 48 used for low bitrate)
The resulting MP3 is 8% smaller when using 44.1, which isn't much, but when I'm trying to get an entire 26-episode season of Enterprise on two DVD-Rom's every little bit helps. I can tell no difference between 48 and 44.1 at 128 CBR; I'm sure VBR would suffer more.

-inst it "commonly" stated that VBR at any average bitrate (and size) delivers better quality than its equivalent CBR bitrate ? where has the cbr < abr < vbr thing gone? were I wrong all this years? hope hell no :)
Depends on the audio - something with a lot of soft music will suffer at those points. I can't stand that "shattery" distortion that comes up at or below 96kb/s. It also depends on how you listen to them - I use 128 CBR and use high-end headphones and my encodes sound great. I'm sure with a high-end stereo there'd be a perceptible distortion at some point, so for big movies I stick with AC3.

You might want to edit out your "general" question - discussions of that subject aren't allowed.

[chilled]

...removed then, in fact I was just curious.

When you say 8 percent smaller do you mean that if I specify the bitrate to LAME and force it to convert to 44.1 (outside AutoGK), the resulting mp3 will be smaller than the same output (i.e. same bitrate) but without enforcing this Khz conversion? I still dont get it: I would understand for a pure VBR encoding, but CBR 128kbps is a constant bit flux which doesnt vary whatever the sampling frequency you choose...

"I can't stand that "shattery" distortion that comes up at or below 96kb/s"

me neither, but with a 112 ABR AutoGK encoding you rarely hear these shattery sounds, because you only go below 96 or 80 when there are low ambient sounds or voices, rarely when FX and music play IMHO.
Anyway I wish I had high-end headphones to hear my probably beloved crappy mono or 96 encodings :)

[jggimi]

...here in Spain downloading a movie you already own......discussions of that subject aren't allowed.Discussion of IP law as it relates to digital A/V is allowed; its just that its off-topic here. What's expressly disallowed here is discussion that condones IP theft, per Rule 6.

I will make two general statements; hopefully this will be enough to satisfy chilled's question: Laws and regulations differ from country to country, and, like technology, are subject to constant change. Worse yet, every existing regulation is subject to varying interpretation. There is no clear answer. In addition, what is "illegal" -- meaning criminal -- and what is merely "actionable" -- meaning civil -- add confusion as well. For detailed assistance, you should consult with an intellectual property attorney who practices in the country in question. As to our forum -- it is a global community. The rule we have adopted regarding our interpretation of intellectual propery rights for A/V material is stricter than the regulations in some countries, and, of course less strict than others. It is based on the principal of Fair Use, as described in the Piracy & Copyright section of http://www.doom9.org/disclaimer.htm.Hopefully, that was enough off-topic discussion.

[Sektion8]

This is, unfortunately, a drawback to MPEG-4 compression. It combines several compression methods, and one of them is "blocking" similar colors to reduce the amount of information needed to contain the picture. The lower the bitrate, the worse it gets. The two most effective ways to lessen this are with smaller resolution settings or a larger end file size.

Yeah, that's the one... Bummer :(

And it'll look worse if viewing on an LCD monitor than on a CRT.

Ah-hah!! Man, you guys are good... I'm running on either my 15"LCD or Sony SVGA LCD PJ... Hmm, what to do... :confused:

How do you know its SD? Final resolution doesn't tell you anything. HDTV is better because its resolution upto 3 times more than on DVDs, so you start with better quality and you end with better quality (and it doesn't matter if final resolution is SD).

It's posted all over "their" info, plus I'm 90% sure it's only broadcast in SD anyway. I've read a little bit about HDTV, and that's complicated in itself from what I see... I know there's almost only two channels here that use *proper* HD, the rest is only a-little higher than SD... sketchy people :(

[Slitheen]

So what are the extra factors that people use in GK that allow for better quality encodes than people using AGK?

Why can they not be put into AKG?

[CWR03]

Because then it wouldn't be "auto." The extra factors allow more control, which AutoGK chooses for you. I don't recall if you can enter the XviD codec setup with AutoGK; it can be fine-tuned with Gordian Knot (and it can also be thoroughly screwed up if you don't know what you're doing).

[Slogra]

The audio... Dunno, I figure constant quality is better than up & down quality.

Remember this:
CBR = Variable quality
VBR = Constant quality

CBR just sucks, you either use too many bits or too less, but never the right amount. This results in variable quality. Unfortunately it's not possible to cut a video with a VBR audio stream, but cutting it usually not necessary.
Look at a VBR video compared to a CBR video with the same size/bitrate. The VBR video will be much better.

ABR is a setting in between VBR and CBR, it is better than CBR but worse than VBR.

VBR > ABR > CBR

[CWR03]

I'm not sure where you get your information from; it's not very accurate, and it's very subjective. ABR isn't a setting between anything - it's based on a single number, say 128, and the "average bitrate" of the entire file = 128, which means it's the same size as a CBR 128. VBR uses a maximum and minimum setting, i. e. 192/64, and the final file is entirely dependent on what the soundtrack contains. "Die Hard" would encode larger than "On Golden Pond," for example.

CBR just sucks, you either use too many bits or too less, but never the right amount. This results in variable quality.
You contradict yourself - constant bitrate = constant quality, which means an encode would be equally distorted throughout if too low a bitrate is used.

[Slogra]

I'm not sure where you get your information from

Hydrogenaudio and own experience.


ABR isn't a setting between anything - it's based on a single number, say 128, and the "average bitrate" of the entire file = 128, which means it's the same size as a CBR 128.

I mean that the quality that you get for a certain bitrate of ABR is between VBR and CBR. The quality will be better than CBR but worse than VBR.


You contradict yourself - constant bitrate = constant quality, which means an encode would be equally distorted throughout if too low a bitrate is used.
I said constant bitrate = variable quality. I meant to say that with CBR, a part of a song (frame) never gets the right amount of bits. The song part will be either too difficult to encode at that number of bits so artifact will occur, or it will be too easy of encode and not all bits will be used and will be thrown away.

[CWR03]

I mean that the quality that you get for a certain bitrate of ABR is between VBR and CBR. The quality will be better than CBR but worse than VBR.
Again, that's a subjective comment, and it's also dependent on the settings used for VBR, as it takes a minimum and maximum parameter. I agree there are advantages to ABR, but there are also disadvantages, such as compatibility with software or standalone players. Back to CBR, at 48.1kb/s and 128 has always sounded great on my hardware, and I never have to worry about synch problems even in a faulty rip. If you or anyone else chooses ABR and it works for you, that's great; it was hardly fair of you to chime in and say "CBR just sucks," because it works well for me.

[manono]

Come on, CWR03, you're not really saying that CBR audio is as good as VBR audio are you? Think of CBR video encoding vs VBR video encoding. You understand that with CBR video encoding static scenes look good, but bits are wasted, while the complex scenes won't have enough bits, and the video may block up or have other artifacts, right? The same applies with CBR vs VBR audio encoding, as Slogra explained. The main difference when encoding VBR video is that you can run 2 passes for a fixed final size, whereas for VBR audio, it's running one pass, and as you said, you won't get a fixed final size or bitrate (unless you choose ABR). It'll take whatever bits it needs within the min and max bitrate you defined. If CBR 128 sounds good to you, that's fine. Maybe you (like me) are listening on lousy computer speakers. But when played in my DVD/MPEG-4 player out to better speakers, I don't want CBR audio, unless it's at a high bitrate, or unless it's AC3.

As for compatibility issues, maybe, but I've never had any problems, such as synch issues, with my player.

constant bitrate = constant quality

I hope you realize that's incorrect. Maybe you'll need a medium to high range audio setup to tell the difference. In any event, use whichever you like, but everything Slogra said was correct.

[CWR03]

manono, you as a mod should know to read the entire thread before posting. One, I never at any time said CBR is better than anything; I said it works for me. Two, I mentioned that I use high-end headphones and my CBR 128 encodes sound great. Last, I had already said that CBR 128 would likely show distortion on a good stereo or surround system, and that I use AC3 for big movies where it would be of biggest concern.