Does proscan make better use of the DV codec? at DVinfo.net

Ignacio Rodriguez · February 12th, 2004, 09:10 PM

Ok here is something that came to my mind after reading about a guy who built his own progressive scan DV camera:

We like proscan because it gives us 'film-like' motion and does not exhibit interlace artifacts, right? That's really cool and I like it too... but I also think there might be another reason to embrace proscan, a reason that makes it important for the camera to do real progressive, not post, not deinterlacing. The real thing.

As I seem to recall, the DV25 codec has no interframe compression, but seems to have some form of interfield compression. Of this is true, than having the same info written to both fields should yield a better image, right? Could that be as good a DV50@60i? If DV25 is said to have a compression ratio of 5:1, would using proscan be actually giving us something like 2.5:1 performance?

Rob Lohman · February 13th, 2004, 05:50 AM

Yes, DV has not interframe compression. I'm thinking DV compresses
each frame seperately, but I'm not sure on that. If both fields
contain the same information then you would loose 50%
vertical resolution unless I'm missing something. I'm also not
seeing how this would decrease the compression level since
both fields will be compressed the same.

Filip Kovcin · February 13th, 2004, 07:51 AM

ignacio,

can you tell me where did you read about that guy who made his own progressve camera?

any links?

thank you

filip

Ignacio Rodriguez · February 13th, 2004, 08:22 AM

Hmm, yes Rob, I had not though about that: each field is only supposed to have half the lines... if the bandwidth allocated for each frame is shared between two fields, then having similar info on both fields reduces compression artifacts but we will not really ever have the same info in each field, so it's not like having two exact same frames in an interframe compression scheme, thus we don't get a dramatic quality gain... probably just a very mild one.

Of course if we are compressing 'Sony-style' line-doubled 30 fps, both fields would have the same info and, as you say, we would have reduced vertical resolution and, as I believe, less compression artifacts. I guess I prefer real proscan though... (sigh)

Filip, the article on the home-built proscan camera is right here in another thread:
http://www.dvinfo.net/conf/showthrea...threadid=21115

Barry Green · February 13th, 2004, 01:12 PM

Both fields do not have the same information.

In progressive-scan, both fields are captured at the same moment in time, but contain very different data.

In interlaced, both fields are captured at different moments in time, and also contain very different data.

Ignacio Rodriguez · February 14th, 2004, 09:44 AM

Right Barry, so basically, I was wrong :-)

February 12th, 2004, 09:10 PM	#1
Ignacio Rodriguez Contributor Join Date: Sep 2003 Location: Santiago, Chile Posts: 932	Does proscan make better use of the DV codec? Ok here is something that came to my mind after reading about a guy who built his own progressive scan DV camera: We like proscan because it gives us 'film-like' motion and does not exhibit interlace artifacts, right? That's really cool and I like it too... but I also think there might be another reason to embrace proscan, a reason that makes it important for the camera to do real progressive, not post, not deinterlacing. The real thing. As I seem to recall, the DV25 codec has no interframe compression, but seems to have some form of interfield compression. Of this is true, than having the same info written to both fields should yield a better image, right? Could that be as good a DV50@60i? If DV25 is said to have a compression ratio of 5:1, would using proscan be actually giving us something like 2.5:1 performance? __________________ Ignacio Rodríguez in the third world. @micronauta on Twitter. Main hardware: brain, eyes, hands.

February 13th, 2004, 05:50 AM	#2
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	Yes, DV has not interframe compression. I'm thinking DV compresses each frame seperately, but I'm not sure on that. If both fields contain the same information then you would loose 50% vertical resolution unless I'm missing something. I'm also not seeing how this would decrease the compression level since both fields will be compressed the same. __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

February 13th, 2004, 08:22 AM	#4
Ignacio Rodriguez Contributor Join Date: Sep 2003 Location: Santiago, Chile Posts: 932	Hmm, yes Rob, I had not though about that: each field is only supposed to have half the lines... if the bandwidth allocated for each frame is shared between two fields, then having similar info on both fields reduces compression artifacts but we will not really ever have the same info in each field, so it's not like having two exact same frames in an interframe compression scheme, thus we don't get a dramatic quality gain... probably just a very mild one. Of course if we are compressing 'Sony-style' line-doubled 30 fps, both fields would have the same info and, as you say, we would have reduced vertical resolution and, as I believe, less compression artifacts. I guess I prefer real proscan though... (sigh) Filip, the article on the home-built proscan camera is right here in another thread: http://www.dvinfo.net/conf/showthrea...threadid=21115 __________________ Ignacio Rodríguez in the third world. @micronauta on Twitter. Main hardware: brain, eyes, hands.

February 14th, 2004, 09:44 AM	#6
Ignacio Rodriguez Contributor Join Date: Sep 2003 Location: Santiago, Chile Posts: 932	Right Barry, so basically, I was wrong :-) __________________ Ignacio Rodríguez in the third world. @micronauta on Twitter. Main hardware: brain, eyes, hands.

February 13th, 2004, 07:51 AM	#3
Filip Kovcin Major Player Join Date: Dec 2003 Location: warsaw, poland Posts: 440	ignacio, can you tell me where did you read about that guy who made his own progressve camera? any links? thank you filip

February 13th, 2004, 01:12 PM	#5
Barry Green Barry Wan Kenobi Join Date: Jul 2003 Location: North Carolina Posts: 3,863	Both fields do not have the same information. In progressive-scan, both fields are captured at the same moment in time, but contain very different data. In interlaced, both fields are captured at different moments in time, and also contain very different data.