"Have you tried the Video4youtube plugin?"

No but I just took a look at it, seems a good way to end up with some horrid results on YouTube. Also it is not a "plugin" and it in no way addresses the issue I was talking about.

The issue is that the aspect ratio known as "16:9" is not exactly the same for HD as it is for SD.

Bob.

Youtube recommends sticking with their default resolutions (at least in one dimension). I've had reasonably good luck upsizing 16:9 SD to 720p for Youtube.

576 vertical (PAL SD) is not one of them.
1080p: 1920x1080
720p: 1280x720
480p: 854x480
360p: 640x360
240p: 426x240

"I've had reasonably good luck upsizing 16:9 SD to 720p for Youtube."

That should work as well. Any standard HD frame size will be converted to SD (480, 360 or 240) by YT without any wierdness happening. My only reservation with upscaling to 720p is if anyone then hit the 720p option for playback it isn't going to look too "HD" and for the one video I used my trick for it doesn't look good even at 480p.

There are several posts on YT's support pages that do suggest using 1048x576 and that does cause issues with a column of duplicated pixels. Seeminly using 1024 x 576 gets around this although I think there's one column of black pixels on the RH side of the frame, far better though than what happened with 1048x576.

Next time I'll try 480p, the SAR is 1.779, SD PAL has a SAR of 1.819 but i can generally afford to crop a bit.

Bob.

Yes, my checklist for youtube is pretty conservative, and using only 16 modulus is one of them. For 16:9 NTSC I use 864x480 (which is actually 9:5). It's actually not a bad ratio to use for general web and streaming delivery.

Other things to avoid for YT uploads are:
Any interlaced content
Anamorphic PAR
VBR Audio
VFR Video
Weighted p-frames
Pyramid b-frames

All of these things can and have caused problems on youtube, including bad audio sync, bad stuttering, garbled output, and just plain sucky quality.

"Other things to avoid for YT uploads are:"

Indeed.

Now here's a riddle.
Why did the the engineers at Sonic Foundry decide 16:9 SD PAL was an odd number of pixels wide when expressed with a PAR of 1:1 i.e. 1049 x 576 ???

There was much debate about this around 10 years ago. The mathematically correct answer rounded up to the nearest integrer is indeed 1049 however that breaks a convention that any SAR dimension must have an even number of pixels. At the time I don't think anyone tweked to the problem of having an odd number of pixels.

Bob.

NTSC square pixels for 16:9 is 853x480. An equally useless number.

Which brings up the deeper question: why 16:9 at all? The only reason I have heard is for "legacy reasons," which makes about as much sense as t*ts on a boar hog.

9:5 and 16:10 (8:5) are both easy enough to work with in one's head, and each provide many more possibilities for mod 16 or mod 8 dimensions. Ridiculous.

It is possible to rendered MainConceptAVC with resolution 1050*576 (square pixel).

"It is possible to rendered MainConceptAVC with resolution 1050*576 (square pixel)."

I suspect it is however why would you?
Vegas gets it wrong displaying it as 1049x576. Rounding that up to the nearest even number only gives a number divisable by 2. The correct value of 1048 is divisable by 8.

"Why not just stick to the 1024 x 576 setting which is a 16x9 aspect ratio?"

Because it is wrong. The PAL SD widescreen format is 1048x576 which indeed isn't 16:9, it's 1.82:1, close to film's "widescreen" 1.85:1.

Bob.

Bob, are you opposed to cropping (in Vegas) to the desired upload aspect ratio?

I've done that with SD to YouTube, and the results weren't completely awful.

Most digital SD formats included extra space "on the wings" for handling the control signals, blanking, and such so that they would be off the screen when shown with normal overscan hidden. This is why both PAL and NTSC DV are slightly wider than 4:3 or 16:9. NTSC SD is 720 pixels wide, but the legal image area is only 704 pixels of that width.

However, as pure digital acquisition became mainstream and analog faded into the dim mists, these extra pixels on the side started being used as actual frame image material instead of being relegated to the nether regions.

I'd suggest that 1024x576 really is right if the goal is to show a "widescreen" frame. Cropping the extra 12 pixels off each side is merely getting rid of pixels that weren't meant to be seen anyway.

Why 16:9 instead of 8:5 (16:10)? I strongly suspect that some group of engineers simply squared the old ratio and got (4:3) x (4:3) = (4x4:3x3). Seems as logical as any other explanation. I do agree though that 16:10 is a whole lot nicer to work with. My previous laptop has a 16:10 display that was wonderful. However, so many users complained to the manufacturer about the 1/4" of black on top and bottom when watching DVDs on those displays that they caved in and my new laptop is a 16:9 display instead. UGH!

Personally, i advocate using whichever frame aspect ratio most suits your material and let the screen shape be darned. Tell me ... when is the last time you heard someone complain that a painting or photograph didn't completely fill the picture frame and there was some matting around the image that wasn't the same size horizontally as it was vertically? Who really cares? Folks who paid a LOT of money for a new HD TV seemed to care for a while, but not so much for artistic or technical reasons but because they felt economically cheated by not having all of their expensive screen area used. That concern seems to have mostly faded now.

I remember the days back yore when the movie theater used to move the curtains at the side of the screen in and out to match the width of the movie frame being played. Often it would change for each individual preview being shown. Now they leave them alone and some movies are narrower and leave blank screen inside the curtains, and some are wider and the image bleeds out onto the curtains. I can't remember hearing anyone in the last 20 years even mention it, much less demand their money back because of it. By and large, the audience just doesn't care. They want to been entertained, not educated about piddly technical issues. Entertain them.

... when is the last time you heard someone complain that a painting or photograph didn't completely fill the picture frame and there was some matting around the image that wasn't the same size horizontally as it was vertically? Who really cares? Folks who paid a LOT of money for a new HD TV seemed to care for a while, but not so much for artistic or technical reasons but because they felt economically cheated by not having all of their expensive screen area used. That concern seems to have mostly faded now.

Faded? I see it all the time .. folks who expand a 4x3 image to fit a 16x9 HD TV .. all I can see is distortion, but they love it.