DVD/DV quality

[Dieter Vansteenwegen]

Sorry if this is in the wrong forum, but at "video" there was a note stating that post-production related things where nog supposed to be posted there.

 

I was wondering some things about codecs...

 

*MiniDV uses MPEG2 compression, right?

DVD also uses MPEG2. Does this mean they are in fact the same format? Or how does this work. So why is transcoding necessary when going from MiniDV to DVD? To change the bitrate?

 

*Is it wrong to think that the MPEG2 format is a progressive format? As far as I remember, MPEG compression works with macroblocks rather than lines, so the interlaced/progressive thing isn't relevant?

 

A friend of mine is thinking about buying a camcorder to film holidays and those things, he asked me which would be best, a MiniDV or a camcorder which records on DVD. I would go for the MiniDV, but I started wondering about which of those two would have the best quality/lowest compression. I suppose dvd has a higher bitrate then MiniDV?

 

At the moment I'm making a small film for a company (I know.... it's to pay the rent :) ). I have been shooting on MiniDV (due to production budget). Editing is done in Premiere Pro. After rendering and exporting as uncompressed AVI, DVD authoring is done with Adobe Encore. Even when using Progressive, high quality 2Pass encoding, the image is quiete bad.

 

Maybe I should have posted in the Newbie forum after all...

 

Thanks!

 

Dieter Vansteenwegen,

Gent,Belgium

[Phil Rhodes]

Hi,

 

> *MiniDV uses MPEG2 compression, right?

 

No. MiniDV uses an intra-frame DCT scheme which is related to the way MPEG-2 compresses I-frames, but there's not much similarity.

 

> *Is it wrong to think that the MPEG2 format is a progressive format?

 

Yes. There are separate schemes under MPEG-2 to compress either interlaced or progressive frames; it's capable of either, depending what you feed it.

 

> I would go for the MiniDV

 

So would I, unless I had a really, really compelling reason to play back my camera media in a DVD player. There is, as you clearly know, a somewhat involved authoring process between a miniDV camera tape and a playable DVD, so there may be circumstances under which this is a good idea.

 

> but I started wondering about which of those two would have the best

> quality/lowest compression. I suppose dvd has a higher bitrate then MiniDV?

 

No, absolutely not - far lower. MiniDV records at 25mbps; DVD maxes out at 8, and most are far lower to fit the whole film on the disc with all the extras. This is why DVD must use temporal compression as well as intra-frame to maintain a workable image at low bitrates.

 

> Even when using Progressive, high quality 2Pass encoding, the image is quiete

> bad.

 

This isn't really the forum for a DVD mastering question, but what d'you mean by bad? If you're shooting interlaced footage and compressing it as progressive, that will make it look bad, as the MPEG-2 encoder will be running itself ragged trying to encode all the interlace fringing.

 

Phil