SVCD: CBR vs VBR

[time4audio]

What gives better video quality

CBR at 2499 kb/s or
VBR at 2379 kb/s (avg) with a max video datarate of 2499 kb/s?

In other words, if the number of CDs would not matter, just the playback capability of the DVD-player (according to the SVCD spec) - what produces the best picture quality?

BR,
t4a

[RadicalEd]

It is to my understanding that VBR will actually produce better results for this reason;

VBR can supply short bursts of higher than max bitrate which are completely acceptable for the SVCD standards and SVCD decoders. So while it may seem like you cant get better than your max bitrate, some of the bits from less complicated scenes can in fact be put to use. Theoretically CBR 2600 kbps video would be the highest possible quality, but using VBR it seems this can be defeated. Anyway even if there were nothing to gain from less bits, you can always benefit because of the smaller size without a real quality loss.

[Twin]

Originally posted by RadicalEd
It is to my understanding that VBR will actually produce better results for this reason;

VBR can supply short bursts of higher than max bitrate which are completely acceptable for the SVCD standards and SVCD decoders. So while it may seem like you cant get better than your max bitrate, some of the bits from less complicated scenes can in fact be put to use. Theoretically CBR 2600 kbps video would be the highest possible quality, but using VBR it seems this can be defeated. Anyway even if there were nothing to gain from less bits, you can always benefit because of the smaller size without a real quality loss.

Acctually, not all standalone DVD-Players can handle that, and sometimes not even the media..

[time4audio]

> Acctually, not all standalone DVD-Players can handle that,

Could you please explain this thought a tad further? According to my tests I have found that my Pioneer 535 is not able to handle CBR at 2756 kb/s total bit rate as Bertel proposes it in his DVD2SVCD package. I stumbled over a rather complicated looking calculation on the net that comes to the conclusion the max. practically usable total bitrate would be 2718 kb/s according to the SVCD spec.

The fact of the mattter is my DVD player does not have problems at 2718 kb/s total data rate nor at 2723 kb/s for _CBR_.

It is true though 2756 kb/s max total datarate is okay for VBR (as far as I have checked.) On the other hand how many hours video material do I have to scrutinize to be absolutely sure. :)


> and sometimes not even the media..

I have no idea about what you say here. :confused:

BR,
t4a

[Twin]

Unfortunatly some players, like mine, can't handle a peak over 2600 (that's totally (video+sound)), when it comes to SVCD. So, try to keep your bitrate under there. So I've had alot of problems with high bitrate VBRs. As described before, a VBR clip can sometimes peak over since it used less bitrate to slowmotion scenes earlier in the clip. Total average in the clip might as well be 2600 but those peaks causes the problem.

[time4audio]

> It is true though 2756 kb/s max total datarate is okay for VBR
>(as far as I have checked.) On the other hand how many hours
> video material do I have to scrutinize to be absolutely sure.


Now I have a picture that when encoded as multipass VBR causes my DVD-player to jerky playback the sound (in one scene). No way it is a clean solution to have 2756kb/s total data rate for the Pioneer 535.

BR,
t4a

[poopity poop]

Listen people...
Do a freaking test
Make a CBR Mpeg-2 file at 2500, 3000, 3500, 4000, 4500, and 5000, and SEE if YOUR DVD player can handle it. Only about 2% of good DVD players can't handle past 5000Kbps. In other words: THere is a 98% chance that your DVD player WILL be able to play SVCD's up to 5000Kbps. Past that it gets choppy. Enough of this magical 2600Kbps max bitrate.
Do you HAVE an SVCD player? No.. you have a DVD player...DVD players HAVE to be able to read up to 9800Kbps on DVD's, what makes you think it can;t read past a wimpy 2600Kbps on an SVCD. Nothing!
Make some damn tests it will take you like 5 minutes.
I always make my SVCD's min 400 MAX 5000, and of course I find the average.

[Faceman101]

No DVD player should handle above 3500 correctly. CD-Roms aren't meant to stream data over that.

Back on track of subject, I find VBR provides a better picture quality and smaller file size. I have done some nice looking CBRs, but VBRs have been better.

[poopity poop]

My Apex drive can handle slightly over 5000Kbps. Like I said.. I made a file that was 5000Kbps and one that was 5500Kbps and my drive could handle the former and not the latter.

Go to VCDhelp.com and look at DVD campatibility and you can look up YOUR DVD drive and see what people post and then you can see EXACTLY what your DVD drive can handle..VCD SVCD, max bitrate, CVD subtitles, X(S)VCD's, etc etc.

No DVD player should handle above 3500 correctly. CD-Roms aren't meant to stream data over that

no DVD drive....CD-ROMS's aren't meant... That was a non-sequitor. I assume you meant DVD drives aren't meant...And what are you smoking, that's only 625KB's/sec, which is like .6MB/sec, which is like nothing. That means it will take 18 minutes t copy a CD to your hard drive. I can copy a CD with an SVCD to my hard drive in a DVD drive in like 3 minutes.

[RadicalEd]

eh.. poop, faceman said DVD player, not drive (and he's right, not many standalones on VCDhelp play above 35-4000 kbps from a CD). Anyway at these bitrates we're getting more into the levels of miniDVD instead of XSVCD. The idea was to create a spec compliant SVCD with the best possible bitrate usage. What I suggested before was not to set max bitrate above 2756, but that when set at this max bitrate, the encoder will still supply quick bursts of bitrate above the max which, because of the stream's padding, do not interfere with the spec or the decoder. I'm positive there was a thread on this.. in fact.. hang on and let me see if I can find it..
Okay, well this (http://forum.doom9.org/showthread.php?s=&threadid=18508) thread was somewhat similar and Mark's reply seems to back it up a bit, although I'm almost certain that I read somewhere about the peaks being padded so that players would never have a problem with them.. well anyway thats all the semi-knowledge I can offer for now (but look for more semi-knowledge in the future, and maybe even some semi-wisdom at that) if any SVCD padding-bitrate-type experts feel so inclined to correct me, please do so ^^'

[Pko]

One problem that appears when using too high bitrates comes not from the chipset being capable of decoding it (DVD player must have chipsets capable of at least 9800) nor from drives not being capable of delivering data fast enough (most DVD players can read CD-Rs at around 4X, and that means that up to 5000 should be possible), but from buffers being depleted... the decoding algorithm must have a complete GOP in memory; the GOPs in SVCDs are large (larger than in DVDs, since a larger GOP means better compression, although responsiveness in FF/REW suffers). So if your "burst" is maintained for some time, the buffer is depleted and the playing stutters and/or A/V desynchronization appears.

When you follow the specs, you are sure that the buffers are allways high enough; if not, some movies will play OK and some not, with exactly the same settings in the same player, and the same movie will play OK in some players but not in others.

Both BBMPEG and TMPGEnc give warnings (bbmpeg even informs you of the possible desynchs and how large they are). If the desynch is larger than 300 miliseconds and lasts more than 1 or 2 GOPs, probably the movie will not play OK in most players.

There are some workarounds, but using them you are introducing more violations to the specification and so more room for trouble, although if you use allways the same player, you can find the "true" specifications for that player (usually, they allow surpassing more or less the official specs of SVCD, but some players for example cannot play video bitrates over 2450 although spec marks 2600 as the limit) and you can use them instead of the official one.

[Linux]

I am a great fan of VBR only because that I want to use less CR-R and mostly does not mind the picture loss.

Some thing that have been overlooked in this subject is that MPEG-2 says that the movie should be VBR. This meens that SVCD with CBR is more or less a VBR with min and max avg. set to the same. When the encoder does not need that many bits, it is using padding to keep a constant bitrate.
So all the talk about burst rates applies with CBR too. It applies to true CBR also because when using CBR the encoder is using a bitreservoir so it can use more bits when needed within a small timeframe.
Because a ordinary DVD movie is using between 5 and 9 Mbit/s the recompression is so large anyway that padding is nearly never neaded.

At last.
CBR (pseudo) can make better quality than VBR at the same bitrate. The reason for this is that it is hard for the encoder to find out when it is possible to save bits. So the difference is not in the action part that is using a lot of bits because there the VBR is running at max anyway. The differece will be in slower parts and other sections that the encoder believe to be easy encoded.

PS. My DVD-player cannot correctly sync a SVCD when the video bitrate exceede 2600

[rixkix]

Take a look at the original question - the CBR is the same as the VBR max. THe VBR won't look better unless you give it a higher peak.

[emilius256]

CBR encoding is faster then VBR but create more cd then VBR, so if you want good quality with slow machine and don't mind how many cd you'll use choose CBR.
VBR give less cd but it's slowly.

The quality is almost the same, so at end the question is, you prefer a fast encoding but more cd or less cd but slow encoding ?

Bye.

[time4audio]

Thank you. That was the essence of my question. I think I have got it now.

BW,
t4a