[vdr] Re: improving tosvcd 0.9 MPEG quality.

[Steffen Barszus <st_barszus@gmx.de>]

On Sunday 16 February 2003 16:52, you wrote:
> Hi,
>
> I believe tosvcd is a great tool: it does exactly what you
> want, is very easy to use and has nice features, such as
> making best use of the available CD space.
>
> However, I noticed that the quality of the MPEG-2 video material
> created by tosvcd is very poor - even in "-q 1" mode. Block artefacts
> all over the place and seams along lines are quite common. The images
> look like a JPEG picture that was saved with low quality settings
> (20% or less).
>

It is not so bad, at least on TV, but it depends on the material. mpeg2enc has 
some problems with dark movies

> I used to create VCDs using an SGI O2 by capturing analog video
> material via the O2's capture hardware and by compressing that
> into MPEG-1 using SGI's dmconvert utility. The quality of these
> VCDs was much, much better than the quality of the SVCDs created
> by tosvcd. One would assume the opposite. Should not SVCDs be
> better than VCDs?
>

It depends on the compression and how many minutes you try to stuff on one CD.

> I assume that the encoder used by tosvcd (mpeg2enc) is the culprit.
>

Yes

> So my questions are:
>
> 1) Is there anything that can be tuned in the call parameters
>     to mpeg2enc to create a better MPEG quality?
>

Have a look at the mencvcd in the mplayer TOOLS/ dir, and make some 
Comparisons, look at the manpage of mpeg2enc to look what they are doing.

> 2) Is there tuning work in progress in mpeg2enc that will
>     produce better quality in the near future?
>

Steven Andrews has begun to work again on mpeg2enc. One thing he is 
programming on is twopass mode , thats good for better size prediction and 
better usage of the bitrate. Lets wait which features he tries further to 
implement. (loog at the mjpegtools-ml-archiv)

> 3) Is there a better MPEG-2 encoder available for Linux
>     that could be used by tosvcd instead of mpeg2enc?
>

No. there is a sort of bbmpeg in transcode, but bbmpeg is not really better in 
any way. Further transcode is unneeded overhead.


> 4) AFAIK, TMPGEnc is usually the winner when various MPEG encoders
>     are compared. However, TMPGEnc is only available for Windows.
>     Would it be possible to use the TMPGEnc encoding engine under
>     Linux in a way similar to the way mplayer uses windows codecs?
>

Not exactly right. Usually CCE is the winner, but you cant afford CCE, cause 
it costs nearby 2000 EUR. TMPEG is a standalone programm, so it is not 
possible, unless they port the kernel of that encoder to Linux. Otherwise 
TMPG can be started under wine, but you will miss the easiness of tosvcd. All 
other Encoders are usually far behind. I have even seen a comparison, there 
mpeg2enc was the second best after TMPEG. If you wish so, I can search a bit 
and post a link.

> 5) Could the original MPEG-2 data be filtered (without re-encoding)
>     so it would be playable on an SVCD at least by some DVD players?
>

Not really. 
Theory:
-Remuxing would make the recordings in legal mpeg2. That could be burned on a 
MiniDVD (DVD-Structure on CD-R)

Real world:
- There aren't a lot of dvd-standalone , who there able to play these mini-dvd
- For svcd the resolution is often wrong, the bitrate is far to high (highest 
legal bitrate for svcd is 2732(<== is that right ?) with audio). 
- you would have more to do on disc-changing then on watching anything (5 CD's 
for each normal movie)
> Carsten.

-- 
Regards
Steffen
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