green bar on youtube clip

[Renton Maclachlan]

I posted a clip onto youtube the other day and on youtube it shows a thin green bar down the right hand side of the screen, the same colour as my green screen...(the project involves GS tracks...)

The green bar does not show in the Vegas preview window nor on a DVD I cut from the same project.

Any ideas what is happening?

[Leslie Wand]

it's to do with frame output size - sorry can't be more informative, but there's a thread over at scs forum about it somewhere...

[Christopher Young]

Leslie is correct. BTW how are you Mr. W?

There are some anomalies though.

I had the same problem in Vegas 11 but not in 10 using the same input file, which is rather odd. It looks as though V10 can handle non-compliant dimensions but V11 can’t. I haven’t tested V12 as yet. Non-compliant dimensions are dimensions that don't meet with the H.264 Modulus 16 macro block encoding requirement.

Basically it sounds like an H.264 clip you are putting out. If so for H.264 encoding, if done correctly, the width and depth of the encoded file should be divisible by 16. This is called Modulus 16. Example, a render out of 848x480 complies with the Mod 16 requirement as both those dimensions are divisible by 16.

Now take the commonly used 640x360 pixel dimension you see around the web and you will find that the 640 is divisible by 16 but the 360 height is NOT. Divide 360 by 16 and you get 22.5. Therefore this does not comply with Mod 16. It does however comply with the Mod 8 and Mod 4 requirement as 360 is divisible by both 8 and 4 as is the width of 640.

Why all these Mods you may well ask. H.264 is designed around encoding macro-blocks of 16. To get the best quality encoding try to ensure that your video output encodes comply with the Mod 16 requirement. In other words that 640x360 encode should actually be 640x368 as both those dimensions comply with Mod 16. 640x360 will encode well in many encoders if they can encode in Mod 8 and mod 4. By doing this though you are forcing the encoder to drop to that Mod 8 or 4 mode of encoding which whilst it will work is not giving you the best the H.264 encoder can produce. Only Mod 16 output compliance will give you the optimum quality.

Try re-encoding out of Vegas again but this time using dimensions that comply with Mod 16 and I think you will find the narrow green line has now disappeared. As I said it was somewhat odd that V10 was able to handle a non-compliant pixel dimension and render without the green line but V11 couldn’t. Go ask?

Personally I find the best MP4 encodes come out of a free piece of software. Yes FREE! It is called ‘Handbrake’. It is an H.264 encoder but it utilises the latest iteration of MP4 encoding which is x264. No full stop just x264. x264 is very hard to beat for producing super clean MP4 files. Handbrake is slow as it doesn’t use multi-processor power while encoding but it’s worth the wait for the results. It’s also quite sophisticated so does require some getting to grips with to understand all the settings available. Go to Youtube and you will find about ten lessons on how to use Handbrake to best advantage.

Chris Young
CYV Productions
Sydney

[Leslie Wand]

hi chris!

still living up here in paradise....