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View Full Version : Divx ->SVCD with subs on the lower black border : feasible w/o further quality loss?


Pierre C
25th October 2003, 00:08
Hello,
I'm trying to to convert a DivX to SVCD with (permanent) subtitles where I want them, that is out the image, on the black border underneath, without too much encoding in order to limit quality losses. I'm sorry if this already has been covered but truly I looked hard. I found hints at avisynth but it seems a difficult tool to use.

Anyways :
An "Almost there" solution is to frameserve the avi with Virtualdub to TMPGenc (http://www.afterdawn.com/articles/archive/divx_with_subtitles_to_vcd.cfm), with a sub filter (I use the SSA filter). "Almost there" because the video is only encoded once (= less quality loss than with compressing to a new divx and then encode to mpg). However, the subs stay on the picture. When putting a negative value for vertical position in the ssa file, TMPGenc, when encoding, just adds the lower border over the text and most of it is hidden.

Now, I got the idea of first making an MPG file without subs and then frameserve it, with the sub filter, from Virtualdubmod to TPMGenc. Since the borders already have been encoded the first time, I get the subs exactly where I want them.

So, my questions are :
- Does encoding mpg to mpg causes further loss of quality? I've run a test and it looks okay but my eyes are a poor judge :) Confirmation?
- If yes, is there a tool that makes quality comparisons between mpg files?
- Does anyone have an alternative (bleedin' obvious) solution?
To sum up : is it worthwhile or does the loss of quality ruins it and I should just be happy with subs at the bottom of the image?...

Annex (and probably idiotic) : Why does Virtualdubmod take MPGs and not Virtualdub or Nandub?

Thank you for your help (on this one and for all the help I got from reading this forum) (hope I didn't break any rule)

/Pierre

killingspree
25th October 2003, 11:49
hi and welcome to the forum!

although avisynth seems difficult to use i would still suggest to use it. i am sure, that with a little help from this place you will get your desired results in this way.

to your questions:
1) no it's not possible to reencode an mpg without quality loss. it might not be visible, but especially when already encoding from a divx (=heavily encoded source) it would definitely not be a good idea to encode it one more time than necessary.

2) avisynth can compare certain aspects of the video luminance, croma, ... :)

3) as i said above, doing the avisynth script isn't too hard. you can even base your script on a script created by DVD2SVCD and just modify it to fit your needs...

Annex: VirtualDubMod is a combination of many earlier virtualdub modification. amongst others nandub and a version of virtualdub that supported mpg...

hth
steVe
PS: nope you didn't even come close to breaking any rules :)

Pierre C
25th October 2003, 15:20
So I passed the doom9 forum initiation test!? Cheers ;)

Thank you for your answer Killingspree.

Well, AVIsynth, here I come...
/Pierre

killingspree
25th October 2003, 20:50
you most definitely have! ;)