Quantcast KVCD vs. VCD vs. SVCD ? - digitalFAQ.com Forums [Archives]
  #1  
08-22-2002, 06:23 AM
obrigado obrigado is offline
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after several success stories using KVCD
strategie (recent story: apocalypse now,
director's cut, 185 min on 2 CD80,
GOP 18/3, active video area 448x416, 25
PAL) I compared the filesize of different
samples coded in MPEG1 and MPEG2.

To my
surprise the filesize only differs in about
1% or less if keeping all other parameters
constant. One sample resulted in
an even smaller MPEG2 filesize compared
to MPEG1. But this could be the result
of the different encoder.

Another surprise (mentioned this
b4) was after remuxing a TMPGenc coded
file by BBmpeg the filesize was smaller than
the original TMPGenc file (again about 1%,
no recoding!).

So if I choose MPEG2 I'll get much closer
to the standard compared to MPEG1
(VBR, different resolution, variable VBV
etc) for the price of very few more
required diskspace. Even raising
Z-resolution to 10 bit (impossible in
MPEG1) didn't lead to a significant
larger filesize.

Someone out there in netland with
similar experience?

Obrigado
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  #2  
08-22-2002, 07:15 AM
kwag kwag is offline
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Hi obrigado,
You're probably seeing this effects, because you encoded with KVCD's Q.matrix and extended GOP.
If you try the same thing, but using the default Q.matrix that comes with TMPEG and the standard GOP 1-5-2-1-0, you'll probably notice a much larger file size created when encoding a MPEG-2 file.

-kwag
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  #3  
08-22-2002, 08:08 AM
obrigado obrigado is offline
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-> KWAG

>You're probably seeing this effects,
>because you encoded with KVCD's
> Q.matrix and extended GO

yup,

this is what I've tried to express:
once a movie is encoded no
player/decoder can ever recognize,
what q-matrix was
utilized at encoding time. So this can't lead
to problems in the future.

so there s just the GOP structur remaining
incompatible to the standard @ MPEG2.
Even x=352 conforms to MPEG2,
unfortunatly not to SVCD. But I haven't
heard about any problem yet.

But in MPEG1 nearly all parameters of
KVCD strategy are incompatible.

I could imagine this might lead more likely
to more problems (say in 10 years) in
future S/A players than MPEG2.

So
if there are no other major differences/
advantages (?!? are there others ?!?
side effects?!? experience?!? -> my
question)
why not using MPEG2/SVCD ?

I guess it's worth to think about it.

Obrigado
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  #4  
08-22-2002, 08:44 AM
kwag kwag is offline
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Quote:
But in MPEG1 nearly all parameters of
KVCD strategy are incompatible.

I could imagine this might lead more likely
to more problems (say in 10 years) in
future S/A players than MPEG2.
Well' I don't think so! As a matter of fact, the majority of new players are actually more compatible playing almost every XVCD mode, than players manufactured a couple of years ago. So future generations of decoder chips are showing better support for MPEG-1. Not the other way around.

Quote:
So
if there are no other major differences/
advantages (?!? are there others ?!?
side effects?!? experience?!? -> my
question)
why not using MPEG2/SVCD ?

I guess it's worth to think about it.
At least with TMPEG, the quality generated in MPEG-1 is far above the one created in MPEG-2. Under the same parameters. Right now, the best quality is created with the KVCDx2 PLUS templates, which are MPEG-1. Not with the KDVD or SKVCD templates which are MPEG-2. Also, there are far more DVD players in the market that support VCD(XVCD) than players that support SVCD. Even the newer models support more VCD's than SVCD's.

-kwag
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  #5  
08-22-2002, 09:15 AM
Rookie Rookie is offline
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>At least with TMPEG, the quality generated in MPEG-1 is far above the one created in MPEG-2. Under the same parameters.

Many People form other forums discussed this and did lots of tests drawing another conclusion. With TMPEnc 2.5x the quality is the same with anything higher in resolution than standard VCD. Plus you get all the goodies like subtitles and 2 audio streams. Orginally mpeg1 was developed for low bitrates/resolutions and mpeg 2 for med to high bitrates/resolutions.
I for myself have dumped mpeg1 completely.

>for this is what I've tried to express:
>once a movie is encoded no
>player/decoder can ever recognize,
>what q-matrix was
>utilized at encoding time.med to hight bitrates/resolutions.

Of course they can and they must! The used Q-Matrix is embedded in the stream and used for decoding. Imagine what mess an player would produce if he always uses the standard mpeg1/2 Q-Matrix when the film was encoded using an high compression custom Matrix.

cheers

Rookie
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  #6  
08-22-2002, 10:20 AM
kwag kwag is offline
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Quote:
Originally Posted by Rookie
>At least with TMPEG, the quality generated in MPEG-1 is far above the one created in MPEG-2. Under the same parameters.

Many People form other forums discussed this and did lots of tests drawing another conclusion. With TMPEnc 2.5x the quality is the same with anything higher in resolution than standard VCD. Plus you get all the goodies like subtitles and 2 audio streams. Orginally mpeg1 was developed for low bitrates/resolutions and mpeg 2 for med to high bitrates/resolutions.
I for myself have dumped mpeg1 completely.
Yes, you have switcheable subtitles for SVCD's. The problem is finding a player that supports it
Take a look on the other forum, and see how many people can actually "switch" subtitles on SVCD's(CVD's).
As for the statement discussed, I myself have done so many tests, and on the latest versions of TMPEG ( 2.56,57 ) the quality is almost the same now. But I will stick with MPEG-1 for standalone player compatibility. If the day comes that most DVD players support SVCD ( or a variation on MPEG-2 ), then I'll switch and encode in MPEG-2. Right now there's just not enough players out there playing SVCD, compared to the amount that play (XYZK)VCD's

-kwag
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  #7  
08-22-2002, 01:30 PM
obrigado obrigado is offline
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-> KWAG

>quality generated in MPEG-1 is far above the one created in MPEG-2.
>Under the same parameters. Right now, the best quality is created with
>the KVCDx2 PLUS templates, which are MPEG-1.

my idea was different:
don´t change the template, just switch the encoding to MPEG2 in
VIDEO menue. Keep the *PLUS-Template, don´t modify GOPs or
Q-matrix. This way I don´t see any difference in quality
(0.k.:I have to swap the CDs which takes a while, can´t compare 2
screens directly). This way it would be easy to offer a *PLUS template
for MPEG2 too (for all those guys not able to select MPEG2).

>If the day comes that most DVD players support SVCD ( or a variation
> on MPEG-2 ), then I'll switch and encode in MPEG-2. Right now there's
> just not enough players out there playing SVCD, compared to the
> amount that play (XYZK)VCD's

well, if I follow the reports about S/A players in vcdhelp.com I´d not
be that pessimistic. Most devices are reported to play SVCDs
(o.k. I didn´t read each and every report)

-> Rookie

> The used Q-Matrix is embedded in the stream and used for decoding.

after all I read about this the resulting signal/code is of course different
depending on different matrices. So the result of the matrix-based encoding is in every frame but the process is irreversible, you can´t
extract the matrix out the frames.
But - as MPEG is a streaming technique, where
you can start anywhere in the middle and find all neccesary decoding info
after some reading - there had to be a q-matrix replika in every GOP ?!?
Never read it that way.

Can you recommend an URL about this for further reading pse.

Obrigado
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  #8  
08-22-2002, 01:48 PM
el_mero_zooter el_mero_zooter is offline
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my other apex 1500 handles switchable subtitles and second languages on svcd's (480x480 compliant and non-compliant). I usually add a spanish or french audio track to go with the english one and switch between the subs in english or subs in french/spanish.
They dont work well on 352x480 mpg2 svcds or (kvcd) or mpg1, or i missed a step somewhere..

ztr
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  #9  
08-22-2002, 02:45 PM
kwag kwag is offline
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Quote:
Originally Posted by obrigado
This way it would be easy to offer a *PLUS template
for MPEG2 too (for all those guys not able to select MPEG2).
That's what the SKVCD and KDVD templates are

-kwag
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  #10  
08-22-2002, 04:22 PM
Rookie Rookie is offline
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Quote:
Originally Posted by obrigado
-> KWAG



-> Rookie



> The used Q-Matrix is embedded in the stream and used for decoding.



after all I read about this the resulting signal/code is of course different

depending on different matrices. So the result of the matrix-based encoding is in every frame but the process is irreversible, you can´t

extract the matrix out the frames.

But - as MPEG is a streaming technique, where

you can start anywhere in the middle and find all neccesary decoding info

after some reading - there had to be a q-matrix replika in every GOP ?!?

Never read it that way.



Can you recommend an URL about this for further reading pse.



Obrigado


At least Restream written by shh can change the Q-Matrixes in the sequence header of mpeg2 streams. Dunno if theres an tool suitable for mpeg1 streams too.


EDIT: Forgot that bbmpeg can also change the Q-Matrix when muxing.


---snap&paste from the Readme----

Intention:

===========

- change/insert/strip/save manual matrices. This is to fix faulty streams

wich lack of the correct matrices. (e.g. from bad demultiplexors or from

a patched CCEv2.50)

- correct top-field-first flags

- change aspect-ratio or framerate

- change the nominal bitrate (needed for some authoring-programs)

- disguise a SVCD-stream as a half-D1 stream (needed for some authoring-programs)

---------------



http://shh.dvdboard.de/





cheers



Rookie
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