cvd bitrate parameters, what makes svcd so special?

[freak_in_cage_10k]

Hi All,

i have recently got into CVD and i have one question about it really! i use dvd2svcd and CCE 2.50. I have been making svcds for ages now and i have always used the following bit rate parameters:

Max 2530 Min 300 Max Av. 2230

With the above i have recieved good results and have no probs getting good quality, and 1 hr per cd.

however, i was following the guide made by sefty (https://www.videohelp.com/forum/userguides/98177.php) and he reccomends using the following settings for CVD:

max 2520 min 1200 max av. 2300

Surly these settings are inferiour as the credits would get at least 1200kbs. isn;t this inefficient? should the settings be more like the svcd ones above???

cheers everyone!

[vitualis]

Hi All,

i have recently got into CVD and i have one question about it really! i use dvd2svcd and CCE 2.50. I have been making svcds for ages now and i have always used the following bit rate parameters:

Max 2530 Min 300 Max Av. 2230

With the above i have recieved good results and have no probs getting good quality, and 1 hr per cd.

however, i was following the guide made by sefty (https://www.videohelp.com/forum/userguides/98177.php) and he reccomends using the following settings for CVD:

max 2520 min 1200 max av. 2300

Surly these settings are inferiour as the credits would get at least 1200kbs. isn;t this inefficient? should the settings be more like the svcd ones above???

cheers everyone!

I'm sure this will go into countless debates, but I agree with you. In a perfect encoder, the minimum should be 0, the maximum should be the max. available and the average is whatever you want the size of the final clip you want.

I consider a min of 1200 to be relatively inefficient.

Regards.

[freak_in_cage_10k]

hmmmm, ok m8, perhaps i will set the min to be a bit lower.

HOWEVER, to make thing more complicated, i was reading the following guide (http://www.doom9.org/index.html?/mpg/dvd2svcd.htm the advanced version) and it quotes that "

Tip
Some release groups enforce the following: "Minimum average video bitrate should not be
lower than 1600kbps for widescreen releases and 1850kbps for full screen releases." If you agree check Min. Avg and put in 1600 or 1850 to guarantee the bitrate.
Bitrate show in the range does include both Audio bitrate and Video bitrate. "

so, i guess i will have to live with this inefficient min bitrate, for the sake of compatability? Do you know how accurate the above is? perhaps it is oly valid for very old dvd players? i would much rather have credits at a v low bitrate and use have bigger bitrates for action scenes!! Whats your opinion m8? any advice would be appreciated!

PS i kow this is a very open topic, and one which is liable to much debate, i am not trying to start an argument or anything but all opinions are welcome!

[adam]

Some DVD players do have problems playing low bitrates, though this is very rare, but just about any SVCD compatible DVD player should also be able to play VCDs. So I would think these players would at least be able to handle 1150kbits.

Anyway, I can tell you that release groups are probably the last people you want to get advice on regarding encoding.

You should be fine using a minimum bitrate of 0-300, and any higher may actually decrease quality. In reality, even with a min of 0 set, you will probably get a min of more like 500kbits.

[macleod]

been doing CVD's for awhile. I personally like them. The settings that you have a good. I would recommend that you make the min. 300, just to prevent DVD player issues.

Also, when you decide to put those movies onto DVD-R, be sure to encode them at 48mhz and be sure to CLOSE GOP's. That can be found on the advanced button at the bottom of the encoder tab.

[ZippyP.]

My Apex 1200 doesn't like the bitrate too low so I set min. at 400 with padding enabled (of course).

[freak_in_cage_10k]

ok, thanks a lot everyone, having read it all i think i will change my min to 300 but keep the av the same.

macleod- i already have the audio at 48Khz, i know this is less compatable but will make things easier when it comes to putting them on dvdr. with regards to closing GOPs, if i do this when i make a CVD will this make it less compatable with standalone players???? i would rather do it now to make putting it onto a dvdr EASY!!!

cheers m8!!!

[adam]

Closed or open GOPs have no effect on compatibility with either the DVD or (S)VCD standards. Closed GOPs are generally only used on multi-angle footage or when alot of editing must be done on the footage. Closing GOPs will only lower quality. One of the biggest advantages of CVD over SVCD is that you can avoid having to re-encode your video at all to transfer it to DVD, so there is no need to go through and re-encode it with closed GOPs.

Unfortunately, I have noticed a bug on at least some versions of TMPGenc where anamolies happen if you don't close the GOPs. It seems TMPGenc does not adhere to your set GOP length when GOPs are left open. So this could actually make your DVD non-compliant, even though it shouldn't.

[macleod]

although referenced in other posts from other folks, I don't think the loss in quality will be noticeable.

I have about 200 CVD's to date. For the longest time, I never closed the GOP's. Then when I got my dvd burner and started trying to put 2 movies onto a DVD-R, I would 90% of the time receive a GOP error (used MF2). I have not found a way to fix the GOP issue without reencoding. Every once in awhile I get lucky (so far only Toy Story worked) with one of my non GOP closed CVD conversion to DVD-R.

After learning my mistake, I ALWAYS close GOP's. I do not notice a difference between the two on my 32" toshiba (bought in 2003).

What I do with all of my CVD's is use DVD2SVCD with CCE 2.5 (2 pass on widescreens, 3 pass on 4:3) image priority at 17 and CLOSE GOP's.

Take it for what its worth. In a year when burners are $10 with rebate (oh, I wish), you'll be kicking yourself....

[adam]

I agree, closing GOPs might not result in any noticable quality loss, but it can. What did you have your GOPs set to in CCE? If you had it set to anything other than M=3 and N/M-4 than your GOP settings are non-compliant with the DVD standard regardless of whether your GOPs are closed or not. In CCE there is really no reason to close GOPs for DVD authoring.

Only TMPGenc does it seem to produce problems.

[vitualis]

Unfortunately, I have noticed a bug on at least some versions of TMPGenc where anamolies happen if you don't close the GOPs. It seems TMPGenc does not adhere to your set GOP length when GOPs are left open. So this could actually make your DVD non-compliant, even though it shouldn't.

Does the newest versions of TMPGEnc still have this problem? I know for sure that v12b (which was the last time I looked at this problem) definitely had a problem with this (which also affects entrypoint placement for S/VCDs) as described here: http://www.michaeltam.com/chapters.html

Regards.

[energy80s]

Always close your GOP's it doesn't make any real difference in picture quality but does make the file more compatible with DVD authoring software. Some packages throw up their heads at open GOP's. Like wise some don't like bitrates below a certain value (and lets face facts that MPEG2 at low bitrates is dreadful anyway). It's pointless trying to get small sized encodes if they don't end up working with other software.

[adam]

Perhaps some lower end authoring programs do have problems with video encoded with open GOPs. I really have no idea, but obviously this shouldn't happen. If you are using TMPGenc as an encoder, however, than this argument completely flies out the window, because as I have already stated, TMPGenc has a bug where the GOP length is not maintained when GOPs are set to open. This really has nothing to do with open or closed GOPs being more compatible than the other, its just a strange bug in TMPGenc.

It should be noted that closed GOPs are basically never used in commercial DVDs except for multi-angle footage. Obviously open GOPs are preferred. So I think you should definitely use open GOPs unless you happen to run into problems with your software. Theoretically, its easy to see why having closed GOPs could lower quality. Whether or not you will actually see a difference in quality is debatable, but the fact is that excluding TMPGenc from the equation, just about any DVD encoding/authoring software combination should work fine with open GOPs, so there is no reason to lower your quality unless you have to.

[energy80s]

Considering that do I use TMPG then closing the GOP's IS the sensible thing to do.

[adam]

Well that's exactly my point. Open GOPs are fully supported in the DVD standard, and are preferred over closed GOPs. Unless YOUR software has a problem with open GOPs, and as far as I can tell this is limited to TMPGenc, than leave GOPs open...period.

Basically, always use open GOPs when encoding DVDs, except if your using TMPGenc.

[freak_in_cage_10k]

macleod- m8 i appreciate your advice but from what others have said your prob with burning the cvd onto dvdr could just be fussy software? i would rather have the quality software and use free trials to establish what software is fussy etc.

adam- i currently have M=3 and N/M-5 yuo mensioned that i should have n/m to 4. will this reduce the compatability of the CVD (until i burn it onto dvdr)???

so, in short, this is what i am going to do to my cvds

Have GOPS open and make sure i dont get fussy DVD burning software (i use CCE so not issues with tmpeg)
keep Audio at 48Khz- not 100% compliant but easy 2 burn onto dvdr
change gop sequence so n/m is 4 (how will this affect cvd compatability?)

thanks a lot for your advice everyone, really helpful!

[adam]

Setting N/M to 4 will decrease the number of frames per GOP, making it compliant with the DVD standard. This will not affect VCD, SVCD, or CVD compliancy. The specs only set a maximum number of frames per GOP. Using less than the max allowed is ok. So at those settings your video will comply with both the CVD and DVD standards. Since you are also encoding your audio at 48kHz, if you choose to convert to DVD later than all you will have to do is remultiplex your audio and video as a DVD.

[macleod]

I receive the GOP error using Movie Factory 2 and sprice up? My settings are M=3 and N/M=5.

What authoring software do y'all use that doesn't give you issues with making a DVDR from a CVD? I would be VERY interested in knowing. Also, is there a software package out there that will fake the N/M=5 to a 4 so I dont have to reencode the darn things??? Actually, if there is a software less fussy, that will fix the issue.

[energy80s]

I use TMPG to create the file and DVD Movie Factory 1.0 to author the file. No problems here.

[VidGuy]

You can get TMPGEnc to adhere to the GOP length with Open GOPS.

I noticed a while ago that it didn't do it (Scenarist complains about the length of some GOPS - very annoying!).

If you go into the "GOP Structure" tab - there's a
"MAX number of frames in a GOP" that defaults to "0 (No limitation)" and it's grayed out. Just type a number (I believe 18 is the correct number for NTSC).....

On some versions of TMPGEnc, it will give you a dialog box about DVD compatibility, etc.... - just click OK.

Voila - the sucker will now import into Scenarist without complaint....

P.S. Even if Scenarist complains - DVDMaestro doesn't, and I haven't noticed any compatibility issues with my 3 players....

[energy80s]

Yes, that is a must - enter either 15 for PAL or 18 for NTSC, but you also have to close the GOPs.

[macleod]

The other solutions require reencoding, but I'd like to get info on a file that was encoded with open GOP's. Sounds like DVDMaestro is an app that will do it.

[kenmo]

been doing CVD's for awhile. I personally like them. The settings that you have a good. I would recommend that you make the min. 300, just to prevent DVD player issues.

Also, when you decide to put those movies onto DVD-R, be sure to encode them at 48mhz and be sure to CLOSE GOP's. That can be found on the advanced button at the bottom of the encoder tab.

What happens if you've created cvds without CLOSE GOP's checked off and now you want to burn them to DVD-R as a DVD ?

[adam]

VidGuy

If you have GOP length set to auto then you have no reason to complain when the length exceeds that allowed by the DVD standard. But the bug I have been referring to is that TMPGenc does not adhere to your SET GOP length. Even if you set TMPGenc to 18 for max frames per GOP, it will still sometimes use more, making your file non-compliant. I actually just tested the newest version and I wasn't able to reproduce this bug, but it always was an intermitten problem so I would not be at all suprised if its still there and its just a matter of time. My guess is that the day this bug is completely removed will be the day that TMPGenc's DVD templates stop setting GOPs to closed, because there is really no reason to do this except to get around this bug.

If you encoded in TMPGenc with open GOPs your file might be fine. Like I said, this bug is intermitten and I can't exactly tell what triggers it. If your file has been affected by this bug, than the only way to truly fix it is to re-encode. You may just be able to author in a less restrictive dvd authoring program which does not check for GOP length, and while overall compatibility on hardware players will probably be reduced, it should play on most players.

[macleod]

I haven't tried them all, but several of them fail when I put them into movie factory 2 and spruce up. They give me a GOP error. I was only able to get toy story 1 to work. The rest have been duds. I am going to buy a copy of dvd maestro and see if that will take care of the problem.

95% of the CVD's that I have done was using dvd2svcd (CCE 2.5) and I never closed GOP's. Oddly enough, since I changed it to close all GOP's, ALL of my CVD's go into MF2 just fine.

[adam]

If you use DVD2SVCD's default settings than your GOPs do not comply with the DVD standards. This has absolutely nothing to do with the GOPs being open or closed, it has to do with the length of the GOPs set. If you use a GOP setting of 3/4 in CCE than your GOPs will comply with the DVD standard regardless of whether you close GOPs or not.

[freak_in_cage_10k]

ok, cheers a lot everyone, especially adam cos you know your stuff m8!

[VidGuy]

Adam,
thanks for the info - I guess I've been lucky so far (only done a couple of files with TMPGEnc that way - usually use CCE)....

[VidGuy]

For kenmo -
if you have MPeg2VCR, One of it's tools in the more recent builds is an MPEG video GOP Fixer that will Fix GOP Size errors for DVD compliance.

It appears to do this by encoding new I-frames in, where necessary.

Seems to work OK......

[energy80s]

But would this not drop the picture quality as its essentially a re-encode?