b frames good or bad

[Subwars]

hey guys i've asked this question before and the main responce i was getting was that b frames makes your movies come out better.... I personaly can't really see that it does but i've kept on using it... only difference i see is that it increases the percentage on the comp checks.... now the last couple of threads that i've been reading alot of people have been saying that it blurs the picture at high bitrates and really is worse to use the b frames setting.... i try to keep my bitrates up to hopefully get the best picture i can i try not to go anywere under 1300 kbs on the video..... i'm using gknot .27 am i really wasting my time and picture quality having b frames on..... should i just turn it off and what about the gmc should i get rid of that as well and just use the standard divx instead of the pro????? any good feedback from people who know there stuff would be appreciated

[midiguy]

some people are experiencing really nasty problems with b-frames in DivX 5.0.3. (I have not done tests yet myself though, not enough HD space!) there is an image in some other thread (can't remember which one, its somewhere around here) which cearly shows this problem, when b-frames is activated, nasty frames filled with artifacts and pixelation.

as for whether or not to activate b-frames, it depends really. the whole point of b-frames in the first place is to allow more bits to go to some frames, and produce some frames with less bits, that are not as noticable during playback (or are not *suppose* to be as noticable). but if your bitrate is high enough anyways (and if your compressibility % that gknot gives you is high enough), then it may bea good idea to deactivate b-frames, because if there are enough bits to go around anyways, then b-frames could just cause un-needed quality degration.

[Subwars]

what about that gmc?

[Ecuador]

I have not encountered problems with B-Frames with DivX 5.0.2 or 5.0.3, and I always have the option enabled.

As for GMC, I have been advising in my XMPEG guide for beginners not to use the feature since it offers only a slight quality gain in low bitrates while it does not follow the ISO-MPEG 4 standard, resulting to videos probably unplayable on future stand-alone MPEG-4 players.
Well, the first consumer DVD player with DivX support has been released, and it does not play GMC or Qpel avis.

To sum up (my personal opinion),

B-Frames YES, although they are not that essential at high bitrates

GMC NO...

[Teegedeck]

Conceptually speaking, B-frames are always a good idea, even in higher bitrate encodings. Because you'll always have some frames that are compressed more than others (you'll rarely be able to compress something at constant quant=2 and put it onto less than 3 CDs). If that more strongly compressed frame is an I- or P-frame it'll degrade the quality of every following P-frame until the next I-frame. And this can be a noticeable period of time. If the strongly compressed frame is a B-frame on the other hand, the degradation lasts only till the next P-frame, and this is a very short timespan and should go unnoticed in most cases.

If B-frames degrade the picture quality at a given filesize when compared to a non-B-frame encoding, then there is something wrong with the implementation of B-frames, I guess.

[mikeson]

I absolutely agree with Teegedeck.

Btw I don't understand why in DivX 5.0.3 DXN have removed quantizer settings. :confused:
XviD has it since beginning (as far as I can remember) and there is no reason to remove it.

[Ecuador]

Just disable the profiles, and you will be able to use 1-pass quality based encoding, as well as the old 2-pass method.

[mikeson]

@Ecuador:

Not sure if your post was aimed for me... ;)

But I was refering to removal of 'Advanced tab', so I cannot restrict min/max quantizers and change RC Averaging period in 2-pass encoding.

[zulu]

Originally posted by mikeson
I absolutely agree with Teegedeck.

Btw I don't understand why in DivX 5.0.3 DXN have removed quantizer settings. :confused:
XviD has it since beginning (as far as I can remember) and there is no reason to remove it.
according to syskin this will probably be removed from XviD's vfw interface, too.

[Teegedeck]

Well, this would probably cause an uproar... ;)
It wouldn't really hurt, perhaps it would even protect newbies from messing things up, but it would cause an uproar nonetheless.

Can you point us to the thread where sysKin said that, I haven't found any statement like this?

[zulu]

Well, this would probably cause an uproar...

hehe, i think i know exactly what you mean.. :D


Can you point us to the thread where sysKin said that, I haven't found any statement like this?

http://www.everwicked.com/forums/showthread.php?threadid=1778

[Teegedeck]

Well, it's very vague. I think it reflects his personal opinion that it better should be removed. And perhaps he's right. I, too, think that. I'd remove many, many options from the config dialogue. But there's no indication that the majority of developers agree that quant-restrictions should be removed any time soon.

sysKin on the use of quantizer-restrictions in two-pass encoding:

Don't use any. You can easly do something wrong, while using them 'correctly' won't make any difference.
It's one of the options waitng to be removed from VfW configuratuin.

[midiguy]

I suppose the idea is that the encoder wants the most flexibility when encoding (quants 2-12, etc.) rather than a user "restricting" it. I could see this as benig true if the encoder is intelligent enough or does enough passes. perhaps that's why DXN took out hte "advanced" tab, because of the implementation of the Nth Pass feature. I also heard somewhere on the DivX forum that the old "advanced" settings can be changed through the registry, although I did not look further into it than that.

[OvERaCiD23]

Originally posted by Teegedeck
Conceptually speaking, B-frames are always a good idea, even in higher bitrate encodings. Because you'll always have some frames that are compressed more than others (you'll rarely be able to compress something at constant quant=2 and put it onto less than 3 CDs). If that more strongly compressed frame is an I- or P-frame it'll degrade the quality of every following P-frame until the next I-frame. And this can be a noticeable period of time. If the strongly compressed frame is a B-frame on the other hand, the degradation lasts only till the next P-frame, and this is a very short timespan and should go unnoticed in most cases.

If B-frames degrade the picture quality at a given filesize when compared to a non-B-frame encoding, then there is something wrong with the implementation of B-frames, I guess.

I've always used b-frames in high bitrate encodes (over 1000kbps most of the time ~~> 2 CDs). Using b-frames allows highly compressible movies to be encoded in 1-pass Q2 mode. This saves alot of time. At that high of quality, turning b-frames off does not inrease quality. I have encoded movies @ Q2 with and without b-frames and done frame comparisons. No visible difference; the only difference being the encode w/o b-frames was about 1/4 larger.

Now, b-frames in DivX 5.0.3 are not so hot now. I've done comparisons between 5.0.2 and 5.0.3 (same avs, same encode settings ~~> 1-pass Q2), and 5.0.3 does introduce artifacts. I've reverted back to 5.0.2 and will stay there until the codec has been fixed. I think it's somewhat pathetic that DivX claims to be the future of video (although that's a questionable statement), but can never implement bug fixes quickly (XviD seems to have bugfixes quite soon after they are reported). Also sad b/c DivX is making money off of their codec, you'd think they would satisfy their customers (or maybe they figure so many people use it for free, that it's okay to screw the consumer). Anyways, to sum it up, DivX 5.0.3 sucks balls for 8 months of waiting for a new release (hell, it would suck if I only waited 2 weeks). But won't those ugly encodes from 5.0.3 look rocking on the new DivX players :eek: ;)

[movmasty]

remember that avi doesnt handle b-frames very well.

[Teegedeck]

But that has nothing to do with what we're talking about here...

[Subwars]

Ok then so the pro features arn't a bad thing i'll just keep on using them then :) hopefully the new divx will be fixed up and working as good as xvid in the close furture but guess we shouldn't hold our breath to soon ;)

[movmasty]

Originally posted by Teegedeck
But that has nothing to do with what we're talking about here...
Originally posted by Subwars
hey guys i've asked this question before and the main responce i was getting was that b frames makes your movies come out better....
One answer could be: "in avi no".

:rolleyes:

[Teegedeck]

AVIs are technically horrible containers, especially when it comes to synch issues.

But the container just doesn't have ANY effects on visual quality of B-frames!

OK?:sly:

[movmasty]

not sure about that.... :devil:

[gldblade]

Hmm...One more repetition should do the trick: Containers have no effect on the quality of the video stream itself. Thus, the avi format should not effect B-frame quality.

[Subwars]

Ok Then What The **** you guys just totally confused me in them last couple of posts :P
:confused:

[Evil Andy]

@Subwars
An AVI file is what is known as a container file. It's only purpose is to take a video file, e.g. a divx file, and an audio file, e.g. an mp3 or ac3, and nail them together into one file with some extra info about syncing the two. Only problem is that the AVI file standard is a little old and doesn't work wonderfully well with our spanky new-fangled codecs, most notably variable bitrates in audio files, but Gldblade's correct visual quality shouldn't be affected.

[Phaedras]

Personally, I can't understand why everybody is still using the ancient AVI container, except maybe for compatibility reasons...OGM is so much better you can hardly compare the two. It supports instant seeking, multiple audio/video tracks and subtitles right from the start, plus built-in error correction that makes it perfect for 800 MB Mode 2 CDs. As far as I know it doesn't have any problems with B-Frames either.

[gldblade]

Compatibility is pretty much everything. AVI is built into Windows Media Player. OGM is not. AVI is well-known, and supported by many, many video editors. OGM is not.

When it comes down to it, AVI is easier for the user to use, for now. It just takes time. Patience.

[OvERaCiD23]

Unless you're using multiple audio streams, I see no point in using OGM. I've used AVI as the container for all my movies (over 150), and experience no issues from it (VBR MP3 on about 1/4, rest AC3). Seeking is instantaneous (sp?) for all movies (click where I want, it goes there, no time needed to resync or wait for it to get there). Also, I encode to 2 CDs usually so the 5-10MB in overhead for audio is not an issue either. Kind of an apples vs oranges thing, eh?

[gldblade]

Seeking is instantaneous (sp?) for all movies
1)You have a fast computer. You lucky bastard :D
2)Have you tried demuxing an avi with VBR mp3? The last I heard about it (ok, so it was a long time ago), it wasn't very easy.

[OvERaCiD23]

Originally posted by gldblade
1)You have a fast computer. You lucky bastard :D
2)Have you tried demuxing an avi with VBR mp3? The last I heard about it (ok, so it was a long time ago), it wasn't very easy.

I have a 900mhz P3 Mobile (laptop). :eek: . I use the DivX5 decoder, and BSPlayer/WMP9 (mainly BSPlayer).

I have demuxed many AVIs with VBR mp3, no problems whatsoever. Maybe I am lucky, but I have never experienced any problems with AVI and see no valid arguments against it. OGM may be better, but until I get incredibly pissed off at the AVI container, I will not touch OGM.

[Evil Andy]

With my 1.2 Athlon with clean installs of everything when seeking AVIs in windows media player, divx player or media player classic I regularly get warp speed frame rates as the movie tries to catch up with sound, stalled frames and eventually the player hanging. I get none of these problems with OGM files.

OGM is superior in every way but one and it's a big one:

AVI is well established and most PC visual media players can use it without any fiddling around from the user.

[Manao]

@Evil Andy : There is another drawback of OGM : they aren't easily editable. To be used with VDubMod, you have to parse them entirely before being able to do something with ( demuxing / muxing / splitting )

@OvERaCiD23 : you forgot subtitles, chapters information, and OGG Vorbis soundtracks. They are only a detail, but they add something to the movie. They are playable on linux / mac ( OS X with mplayer ) / windows, and with windows you just have to add one filter ( as for ac3 & wma soundtracks ). Plus, the last twenty movies I made were all with two soundtracks ( and only 3 on two CDs ), I would not have been able to do it with such visual quality with avi, because I couldn't have used ogg.

@gldblade : For an user that just want to play a movie, OGM is a must, because it's a all in one file. They don't have to load their subs, or to name them like the movie. The recent players ( TCMP, BSPlayer, MPC, ZP ) interact very well with ogm.

[gldblade]

I have a 900mhz P3 Mobile (laptop). Unfortunately, that beats my desktop :D

[gldblade]

For an user that just want to play a movie, OGM is a must, because it's a all in one file. They don't have to load their subs, or to name them like the movie. Well...a lot of users don't care about subs.

[mikeson]

@gldblade:

Well...a lot of users don't care about subs.

And lot of them do. It depends... :)

Anyway as it was said already AVI can't handle Ogg Vorbis well and I doubt it will handle MPC (if there will be DS filter ;) )

I'm definitely with OGM and even more with Matroska (hi Christian :) )

[gldblade]

I am in support of OGM as well, but I think most users will not see the need to adopt it.

[Subwars]

just wanting to know about these ogm containers more is there a guide of thread that talks about them into detail how to do a rip with one can i use gknot to set things up and maybe just use vdub to input last settings that it will be an ogm output and i guess i would have to download something so they are suported any info about it would be good if i can get better rips out of these ogm files specialy if i can put ac3 audio into it which from what i have read you can so yeah :)

[jggimi]

From Doom9's glossary...OGM stands for OGg Media which is the name of the Ogg container implementation by Tobias Waldvogel. OGM can be used as an alternative to the AVI container and it can contain Ogg Vorbis, MP3 and AC3 audio, all kinds of video formats, chapter information and subtitles.You'll find Doom9's guide by clicking here (http://www.doom9.org/ogg.htm).

Could you please use punctuation now and then? Not everyone who uses the Forum is a native English speaker. Thanks.

[Subwars]

ok then i've gone though that guide and downloaded the programs and stuff for it. one question from what i can tell do i actually have to encode the movie normally, like you would into an avi file then put that movie file into the oggmux add the audio and then make a new file being the ogg file?

so i still rip the movie with divx as normall with virtual dub

[LeonMcNichol]

Encoding the video is still mpeg4, like you would an avi. So yes, like you would normally.

[Evil Andy]

If you install Subrip be sure you don't have Direct VobSub installed. The two don't get along together.