Quality loss going from .mpg to .avi then back to .mpg?

[ChachiFace]

The questions:

Is there quality loss when converting an MPEGII file to a AVI file for editing then encoding back to MPEGII?

Does it help to encode the MPEGII file at a higher bitrate if it is going to be converted back to AVI for editing then back to MPEGII?

The details:

I encoded my .avi file to .m2v and .wav and put on DVD. Now I want to extract the streams and convert back to .avi to edit then encode back to .m2v and .wav to put back on DVD. Can this be done without quality loss?

Any advice on the above or experience with would help.

ChachiFace

[holistic]

Is there quality loss when converting an MPEGII file to a AVI file for editing then encoding back to MPEGII?

YES

Does it help to encode the MPEGII file at a higher bitrate if it is going to be converted back to AVI for editing then back to MPEGII?

No ~ with a little maybe. "Data" is "tossed" during the compression into MPEG2. You cannot get it back.

I encoded my .avi file to .m2v and .wav and put on DVD. Now I want to extract the streams and convert back to .avi to edit then encode back to .m2v and .wav to put back on DVD. Can this be done without quality loss?

What are you trying to accomplish?

[ChachiFace]

What am I trying to accomplish?

As I mentioned in the post...EDIT. If I have a DVDR with an m2v and wav file on it but I want to edit the footage, can I edit it without quality loss? The reason I brought up the senario with converting it back to .avi TO EDIT THE FOOTAGE then encode back to elementary streams .m2v and .wav is because I had heard that editing .mpg footage is bad. Editing should only be done to AVI. Is this not true? So the big question really is, how do you extract and edit an .mpg file from a DVD without losing any quality?

By editing I mean, cutting and adding transitions, etc...

Thanks..

[theDruid]

Almost any sort of format conversion will lose quality in some way - just as holistic says.

I'd say the best you can hope to do is convert the MPEG-2 to avi using one of the low compression codecs (HuffyUV, MJPEG etc..) - there shouldn't be too much loss of quality at this stage, although you'd better have a LOT of free disc space if you're talking a full DVD-R's worth of MPEG-2!

Once you've done your editing, you'll need to re-encode to MPEG-2 (as you know), and this is where you can't avoid some loss of quality.

I think the reason holistic asked you what you're trying to achieve is that this is obviously not the textbook way of going about things, because of the re-encoding issue.

I presume you no longer have access to the source from which your DVD/MPEG-2 was made?

cheers,
mcdruid.

[bugster]

IF the editing you want to do consists only of cuts and splices, you should be able to do this with an mpeg cutter/joiner. TmpGenc can do it but be prepared for sync problems (If your mpeg is CBR it should be OK). Other swear by Womble, but havn't tried it myself.

If you want to do anything more complex then take theDruid's advice regarding codecs.

[ChachiFace]

I'll have to give the editing software a try, thanks.

I have plenty of disc space but not worried about that only the quality loss. So is it safe to say that if you capture in .mpg format (example: dazzle) then you really cannot edit the footage without quality loss? Of course I mean advanced editing (cutting, transitions, fade in-out, etc..)

In this case, I no longer have the original .avi file, I encoded it to elementary mpg streams and put it on DVD, now I'm wanting to go back and edit the footage / cut out highlihgts to author into another DVD. Thanks for the responses.