Different rendered file types display differently

[John Rofrano]

[Brian Tallant] “Interestingly, rendering into another MPEG-2 produces a video that is identically sized, which makes me think there is some problem with the way Vegas renders various file types, or there is a problem with the way these media players display various file types. Or maybe there’s something completely different going on…I can’t figure it out.”

The most likely cause is with the media players and the fact that 720×480 does not use square pixels. Some media players read the stream and account for this and some just assume every pixel is square and represents the video incorrectly. There is nothing you can do about this except that when you render video to be watched on a PC/Internet, always use square pixels to avoid this issue.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Brian Tallant]

Thanks, John.

Do you happen to know how to convert 720×480 with a pixel aspect ratio of 0.9091 to an MP4 with square pixels for use on the internet, in such a way that there is no skewing of the original image? I thought it might be 640×480 but that didn’t turn out exactly right, either.

[John Rofrano]

[Brian Tallant] “Do you happen to know how to convert 720×480 with a pixel aspect ratio of 0.9091 to an MP4 with square pixels for use on the internet, in such a way that there is no skewing of the original image? I thought it might be 640×480 but that didn’t turn out exactly right, either.”

Yup. You need to multiply the width of he video by the pixel aspect ratio. 720 x 0.09091 = 654.552. Since you can’t have a fractional pixel, you would round 654.552 up to 655 and render to 655 x 480 PAR 1.0000 to get square pixels.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Brian Tallant]

John,

I tried rendering the video using MainConcept AVC/AAC Internet 480p 4:3, with a custom frame size of 655×480, but it won’t accept the number 655. It keeps changing it to 656.

Can you tell what I’m doing wrong?

[John Rofrano]

[Brian Tallant] “I tried rendering the video using MainConcept AVC/AAC Internet 480p 4:3, with a custom frame size of 655×480, but it won’t accept the number 655. It keeps changing it to 656.”

You’re not doing anything wrong. That particular codec only supports resolutions in multiples of 8 pixels so you had to round up to the nearest 8 pixels. Use 656×480.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Brian Tallant]

Is there a different codec you recommend, or is this one good enough?

[John Rofrano]

[Brian Tallant] “Is there a different codec you recommend, or is this one good enough?”

Nope, ManConcept AVC is the correct codec to be using for Internet delivery. You’re using the correct one.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Brian Tallant]

Hi John,

Still frustrated. I rendered two different MP4’s – one at 720×480 PAR 0.9091, and another one at 656×480 PAR square. When played on the VLC media player these two MP4’s look identical, and yet both look different than the original MPEG-2 (at their original zoom level they’re both shorter and thinner than the MPEG-2, and when played full screen they’re a little wider). I’m not sure where I’m going wrong but I’ll keep fiddling with it, unless you have a suggestion for me to try.

[John Rofrano]

What was the PAR of the original MPEG2? Was it widescreen? Can you post screen shots of what you are seeing so that we can also see?

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Brian Tallant]

There are two videos open in the picture, one on top of the other. The one on bottom is the original MPEG-2 file, which is 720×480 PAR 0.9091. The video on top is the MPEG-4 I made from it, at 656×480 PAR square. As I hope you can see, the MP4 is smaller than the original, both vertically and horizontally. And if I render the MPEG-4 as 720×480 PAR 0.9091 I get the same results.

More difficult to show is what happens when I look at each video in fullscreen. But basically, when I measure the MPEG-4 in fullscreen, it’s wider than the MPEG-2. I can post a couple of screenshots of each video in fullscreen mode if that would help you.