480I vs 480P

[garyellis]

Can someone tell me the difference between 480I and 480P..(with some explaination, please)...I really want to know if I convert videos from 480I to 480P, are there any problems down the road..?

Thanks,

Gary Ellis

[lobosrul]

480p is progressive aka EDTV, 480i is interlaced aka SDTV or NTSC (analog TV).

For more details: http://en.wikipedia.org/wiki/Interlaced

With the right decoder, ie NVIDIA purevideo, you dont need to "convert" the video. It takes care of upsampling the source to 480p.

Most mpeg4 converters have options to output to progressive. Even that might not be completely necesary with the right decoding filters (not sure on that though).

[stanger89]

It all has to do with Interlaced vs Progressive storage of vidieo, This is probably the best explanation I've seen of some of the issues associated with them:
http://www.hometheaterhifi.com/volum...e-10-2000.html

Now, a couple very important things to consider:
SD is 100%* 480i as a storage/tranmission system. That does not mean that all SD is interlaced though. Far from it, most shows are actually progressive (they come from film).

FWIW, IMO, progressive is always better than interlaced, if you've read, or are aware of all the threads discussing deinterlacing around here, you'll understand why.

Now as for the decision to deinterlace or not, that's kind of a tough question, and what it really comes down to is, try both ways youself and use the one that works best.

As noted above most content is truely progressive and can, and probably should be deinterlaced. Stuff that's shot on video (sports, documentaries, news, etc) are a tougher question, because basically with those you're missing half of each frame. But really, since it's almost guaranteed they'll be scaled, you'll probably want to deinterlace those too.

*I said SD is 100% interlaced, well that's not entirely true, DVDs, which are generally considered SD (though I suppose could be considered HD) are really stored progressively on DVDs, but they are stored as fields not frames.

[garyellis]

Thanks Stanger...my question comes from the "convert" option in the new release of Sage..

I converted a recorded tv show to MPEG4 AVI - high quality...it went from 480I to 480P...so, I wondered if that was a problem or not...and if deinterlace is preferred, there is a conversion option to MPEG4 AVI deinterlaced - high quality..

the conversions obviously save me about 1/2 the space...but before I convert all my saved shows..I wanted to make sure I wasn't making a mistake..

Thanks,

Gary Ellis

[lobosrul]

I think what counts, is if the converted file looks good. I havent really done any encoding with the sage transcoder, but I try and "de-interlace" interlaced files whenever encoding with DIVX or Nero.

[stanger89]

Originally Posted by lobosrul

I think what counts, is if the converted file looks good.

Exactly, the proof is in the pudding as it were.

I was just thinking today that it would be really cool if you could specify an AVISynth script to run the video through when converting....

[ke6guj]

Originally Posted by garyellis

I converted a recorded tv show to MPEG4 AVI - high quality...it went from 480I to 480P...so, I wondered if that was a problem or not...and if deinterlace is preferred, there is a conversion option to MPEG4 AVI deinterlaced - high quality..

I'm currently running at MPEG4 - good quality deinterlaced AVI for most of my "non-important" SDTV stuff. If I convert to MPEG4 - good quality AVI, I get interlacing lines in the conversion.

Do some test runs using both styles and see what looks best for you and uses the least amount of space.

[roxy99]

Originally Posted by stanger89

Exactly, the proof is in the pudding as it were.

I was just thinking today that it would be really cool if you could specify an AVISynth script to run the video through when converting....

I am deinterlacing in my avisynth script- see http://forums.sage.tv/forums/showthread.php?t=21737