What's compressed? Please explain.

Dennis Adams · June 5th, 2003, 07:11 AM

PCM (Pulse Code Modulation) is uncompressed. WAV and AIFF are both PCM.

Pixel aspect ratio doubts come up from time to time. There are a bunch of threads on our forum about it. Trust us, it's right. We've offered a free copy of Vegas to anyone who can prove it wrong.

///d@

Rob Lohman · June 5th, 2003, 08:58 AM

I thought PCM was a lossless compression. Oh well, we learn
every day.

I want to trust you that the PA is right. BUT, every other piece
of software uses a different PA. Both LightWave and DFusion
are being used in a very serious working environment (I'm not
saying that Vegas cannot or is not used there, but I have not
heard of it yet) where it MUST be correct.

If I am not mistaken the calculation for PA is:

Pixel Aspect Ratio = (Overscan Display Height/Overscan Display Width)*Display Aspect Ratio

If I do this for NTSC or PAL I get:

(480/720) * (4/3) = 0,88888888888888888888888888888889
(576/720) * (4/3) = 1,0666666666666666666666666666667

Which are different from Vegas' 0.9091 and 1.0926. Again, my
primary concern is why everbody else (including the high end
packages) are using different PA's then you guys are.

Does this count as PROOF? :)

Hans van Turnhout · June 5th, 2003, 09:58 AM

The below is a quote from a different thread and might shead some light on the differences between Vegas and Premiere in their reporting of the PAR. I think that there is no other difference than what comes from rounding:

"I have done some additional reading and I think that I'm beginning to understand. It seems as Vegas and Premiere uses different basis for the calculation. Vegas seems to use the a method including also the fraction of non-square pixels (702 + 54/59 non square 59/54 pixels per line) that fits in 768 square pixels per line whilst Premiere excludes the fraction. Although the figures differ the visable result might be the same?

Include links to what I have read in case anyone is interested.

http://geocities.com/wunder01au/widescreen.html

and

http://www.mir.com/DMG/aspect.html

(From the thread: http://www.dvinfo.net/conf/showthrea...&threadid=6482)

Rob Lohman · June 5th, 2003, 10:07 AM

Can you elaborate some more on the 54/59 and 59/54 comment?
I'm not following it. Can someone show me a calculation that
gets us the numbers Vegas is using?

Hans van Turnhout · June 5th, 2003, 12:50 PM

I'll try by using the figures in the "mir" link in my previous post.

The PAR for PAL video is 59/54 (i.e. they are 59 wide by 54 high). The AR on PAL widescreen will then be ((59/54)/(4:3)*(16/9)) = 1,4568 (the AR Vegas reports for widescreen).

Premiere reports 1,422 as the PAL AR for widescreen. It seems (I'm not sure) that they have arrived at this number using the formula ((1024/720)/576), in which 720 is the 4/3 ratio and 1024 is the 16:9 ratio if the hight is 576.

Hans

Dennis Adams · June 5th, 2003, 02:59 PM

<<<-- Originally posted by Rob Lohman : Does this count as PROOF? :) -->>>

Hardly. :)

Vegas uses the correct PAR, but if you need to set it to something else in order to interface with programs that got it wrong, we let you set it in the project properties and many of the render dialogs.

///d@

Ozzie Alfonso · June 7th, 2003, 06:33 PM

Gee, and I thought I was asking a simple question. Judging from the lengthy discussion, I see I am not alone in my confusion.

Does ANYONE REALLY KNOW WHY Avid refers to XDV Pro as capable of handling UNCOMPRESSED video? If they mean digital video that is not compressed any more than it already is in its native state, then I can understand, but I thought that is what XDV did from the very beginning. IF Avid means it can handle, say, analog Beta SP, without compression, I also understand; but nowhere has it been described in clear, solid terms.

I’ll keep trying to find a simple answer. By the way, I’ve also asked a few “old time” engineer types who work with Avid MCs, they haven’t been able to come up with clear, positive answers, only guesstimates. So none of us should feel too bad about falling short of understanding.

Rob Lohman · June 10th, 2003, 04:17 AM

Perhaps you should send an e-mail to their technical department
or ring them? (AVID that is).

Richard Alvarez · June 10th, 2003, 08:17 AM

From the Avid website...

UNCOMPRESSED STANDARD DEFINITION VIDEO

Looks like SD 601 to me.

June 5th, 2003, 08:58 AM	#17
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	I thought PCM was a lossless compression. Oh well, we learn every day. I want to trust you that the PA is right. BUT, every other piece of software uses a different PA. Both LightWave and DFusion are being used in a very serious working environment (I'm not saying that Vegas cannot or is not used there, but I have not heard of it yet) where it MUST be correct. If I am not mistaken the calculation for PA is: Pixel Aspect Ratio = (Overscan Display Height/Overscan Display Width)Display Aspect Ratio If I do this for NTSC or PAL I get: (480/720) (4/3) = 0,88888888888888888888888888888889 (576/720) * (4/3) = 1,0666666666666666666666666666667 Which are different from Vegas' 0.9091 and 1.0926. Again, my primary concern is why everbody else (including the high end packages) are using different PA's then you guys are. Does this count as PROOF? :) __________________ 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

June 5th, 2003, 10:07 AM	#19
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	Can you elaborate some more on the 54/59 and 59/54 comment? I'm not following it. Can someone show me a calculation that gets us the numbers Vegas is using? __________________ 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

June 7th, 2003, 06:33 PM	#22
Ozzie Alfonso Major Player Join Date: Nov 2001 Location: New York, NY Posts: 355	Gee, and I thought I was asking a simple question. Judging from the lengthy discussion, I see I am not alone in my confusion. Does ANYONE REALLY KNOW WHY Avid refers to XDV Pro as capable of handling UNCOMPRESSED video? If they mean digital video that is not compressed any more than it already is in its native state, then I can understand, but I thought that is what XDV did from the very beginning. IF Avid means it can handle, say, analog Beta SP, without compression, I also understand; but nowhere has it been described in clear, solid terms. I’ll keep trying to find a simple answer. By the way, I’ve also asked a few “old time” engineer types who work with Avid MCs, they haven’t been able to come up with clear, positive answers, only guesstimates. So none of us should feel too bad about falling short of understanding. __________________ *Ozzie Alfonso* www.ozziealfonso.com

June 10th, 2003, 04:17 AM	#23
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	Perhaps you should send an e-mail to their technical department or ring them? (AVID that is). __________________ 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

June 5th, 2003, 07:11 AM	#16
Dennis Adams Regular Crew Join Date: May 2003 Location: Madison, WI Posts: 123	PCM (Pulse Code Modulation) is uncompressed. WAV and AIFF are both PCM. Pixel aspect ratio doubts come up from time to time. There are a bunch of threads on our forum about it. Trust us, it's right. We've offered a free copy of Vegas to anyone who can prove it wrong. ///d@

June 5th, 2003, 09:58 AM	#18
Hans van Turnhout Regular Crew Join Date: Apr 2002 Location: Sweden Posts: 70	The below is a quote from a different thread and might shead some light on the differences between Vegas and Premiere in their reporting of the PAR. I think that there is no other difference than what comes from rounding: "I have done some additional reading and I think that I'm beginning to understand. It seems as Vegas and Premiere uses different basis for the calculation. Vegas seems to use the a method including also the fraction of non-square pixels (702 + 54/59 non square 59/54 pixels per line) that fits in 768 square pixels per line whilst Premiere excludes the fraction. Although the figures differ the visable result might be the same? Include links to what I have read in case anyone is interested. http://geocities.com/wunder01au/widescreen.html and http://www.mir.com/DMG/aspect.html (From the thread: http://www.dvinfo.net/conf/showthrea...&threadid=6482)

June 5th, 2003, 12:50 PM	#20
Hans van Turnhout Regular Crew Join Date: Apr 2002 Location: Sweden Posts: 70	I'll try by using the figures in the "mir" link in my previous post. The PAR for PAL video is 59/54 (i.e. they are 59 wide by 54 high). The AR on PAL widescreen will then be ((59/54)/(4:3)*(16/9)) = 1,4568 (the AR Vegas reports for widescreen). Premiere reports 1,422 as the PAL AR for widescreen. It seems (I'm not sure) that they have arrived at this number using the formula ((1024/720)/576), in which 720 is the 4/3 ratio and 1024 is the 16:9 ratio if the hight is 576. Hans

June 5th, 2003, 02:59 PM	#21
Dennis Adams Regular Crew Join Date: May 2003 Location: Madison, WI Posts: 123	<<<-- Originally posted by Rob Lohman : Does this count as PROOF? :) -->>> Hardly. :) Vegas uses the correct PAR, but if you need to set it to something else in order to interface with programs that got it wrong, we let you set it in the project properties and many of the render dialogs. ///d@

June 10th, 2003, 08:17 AM	#24
Richard Alvarez Inner Circle Join Date: Sep 2002 Location: San Mateo, CA Posts: 3,840	From the Avid website... UNCOMPRESSED STANDARD DEFINITION VIDEO Looks like SD 601 to me.