Quick question on Half D1 DVD authoring

[catback]

Hi,

I usually author my DVDs at full 720x480 NTSC resolution at an average video bitrate of 4500 kbps. This yields acceptable results for about a 2-hour DVD.

My question is, if I used the same bitrate but used Half D1 resolution, would this yield a better picture? I was going to experiment myself but I wanted to see if anyone has already done a comparison test.

My reasoning is that at half resolution, you have the same amount of bitrate to spread around but now it's at a smaller frame size. This allows that smaller frame to have more detail and video information. However, on the other side, the smaller frame may result in a blurry picture since the DVD player will have to blow up the picture more to fill the TV screen.

Suggestions are welcome. Thanks.

[Matthew]

Put simply:
-high res = more detail but more blockiness
-low res = less blockiness but less detail

Well I tried half res on a noisy PAL source recently (~3100 average bitrate) and the q values according to CCE were substantially reduced. It was definately less noisy.

But the picture looked far too blurry/lacking in detail for my liking (on a computer monitor, didn't try it on a TV).

IMO half res is for when you are backing up extras at low bitrates (e.g. 1500) or something like that, when the result would be lots of pixellation if full res were used.

[hendrix]

i've authored some DVDs at half D1 and it really doesn't look too bad at lower bitrates...i find that interlaced material at low bitrates around 2000k look better if encoded at half D1...it gives the overall picture a more blurry look like a VHS copy - interlaced at D1 res at 2000k bitrate will be macroblocked, if your source is progressive then you really dont need to downsize to half D1 since progressive material encodes better...trust your eyes