Will there be a loss in Quality?

[rrrredrum]

This is a simple question, and I've tried looking for the answear, so please be so kind and don't FLAME me for asking.

If it would be poissible to convert DivX to DivX, using tmpg. Would I loose quality?, I know that if I convert from one compressed format to another I will loose quality, but what if I don't change the format of the file?

I've been trying to find out how to add Subtitles INTO a movie file making permanent subs, but when I read an old post about this some guys said that will result in a lack of quality, when doing this I am not changing the format of the video, and therafor it should not drop in quality.

Or? Could someone please explain thsi to me.

[bb]

Yes, you WILL loose quality, even if you stick with the format, because you still have to recompress.

bb

[Acaila]

Unfortunately it WILL result in quality loss. Whether or not it remains the same format has nothing to do with it. Your original DivX will once again go through all steps that discard fine detail and there's nothing you can do about that.

TMPG only works in RGB colorspace. If you made the original DivX with something that works in a colorspace different from RGB, like Avisynth/VDub which works in YUY2, you will loose extra quality because you'll also have to deal with colorspace conversions. If you made the original also in TMPG you will at least save yourself this loss, but the DivX recompression loss will remain.

[rrrredrum]

Thanks.. damn that is annoying.

[Fox Mulder]

Yes, it is. Try recompressing a 128 Kbps Blade encoded MP3 1000 times. Annoying.

[rrrredrum]

What if I would change the output format of the file, if I encode from DivX to some less lossy format, would that result in less quality loss? If so, which format would you reccomend? (Uncompressed RGB in Virtual takes around 50 gig.

[Acaila]

Any lossy codec will degrade the quality, and since most are based on the same principles as DivX (=block-based) the loss will be about equal.
Re-encoding with a lossless codec will not degrade the quality, but the size will become huge. Unless you really really need to re-encode just leave it as is.

Why you do want to burn the subs into the movie anyway? There is DirectVobSub which can display the subs during playback which not requires the subs to be physically in the movie, i.e. you can have the subs as a seperate file.

You can also mux them into the movie with SubMux, comes with the VobSub package (like DirectVobSub) with which you can take a subtitles file (only specific formats) and mux them into your movie without the need to re-encode. These can then be turned on and off as you desire (with DirectVobSub), unlike burned-in subs which are always on. Note: this doesn't work with VBR MP3 audio.

[rrrredrum]

Maybe I want to watch em on a standalone DVD player..

[manono]

Hi-

Watch DivX on a standalone player? No way. No such thing. If you want to reencode to SVCD, then that's something else (but you didn't say that). It's lower quality to begin with. You could get a decent looking SVCD with your burned in subs. You might try the DVD2SVCD program, which has an AVI2SVCD option.

[rrrredrum]

Acctuly, there IS such thing, I've been thinking about building a Standalone DivX player for some time now, And there are some digital movie players that plays mpeg-4. But I will probably convert it to SVCD. How much quality do you think I would loose from doing a:

Divx + subtitle rencode. And later a Divx to SVCD format conversion?
Someone told me that I could go from Divx to SVCD with permanent subs and only encode, once, altho I never figured out how to do that.

[manono]

Hi-

I think we have different definitions of what a standalone player is. Ordinarily it means a DVD player, whereas you're talking about an HTPC, which of course can play DivX (and with the subs without reencoding, as Acaila explained). As far as I know, none of the DVD-MPEG4 players are out yet, although I agree, it would be nice. Until we see some, I don't know if we can assume they'll play DivX 5.02 or XviD material, although I could be wrong on that one.

I've made plenty of SVCDs from DVDs, but haven't yet made one from an .avi, but if you can frameserve with an .avs, then you can do it all at one time for sure. I was just doing some research on that question. It looks as if you can use AviSource instead of the usual Mpeg2Source when creating the .avs, and you can stick the subs in there using the TextSub plugin for SRT or SSA subs. And of course, the audio will have to be converted to .mp2. But there are plenty of people down in the DVD2SVCD forum that know more about that subject. It doesn't look hard though. My feeling is that if the .avi is of high enough quality to begin with, then the resulting SVCD should look fine.