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Old March 3rd, 2010, 12:29 AM   #1
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Black Bars on Sides when I render to 4:3?

I am trying to produce a short video for upload to Amazon. They require a 4:3 aspect ratio. I have shot the footage in AVCHD 1920X1080. With the advice I received in an earlier post, I then changed my Project Properties to a custom setting of 1440X1080. I then clicked the Pan/Crop button on each video event and selected "Match Output Aspect". This seemed to do the trick. Then when I rendered it (720X480, square pixel, progressive) I ended up with thin black bars on the sides of the image.

I tried changing the Project Properties width slightly ( 1445) but it had no effect. I also tried changing the render width manually to (725) and it would automatically change it to (736) but it did not eliminate the bars either. Anyone know how to fix this? Any help would be appreciated. Thanks.
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Black Bars on Sides when I render to 4:3?-black_bars.png   Black Bars on Sides when I render to 4:3?-black_bars_render.png  

Jamie Dull is offline   Reply With Quote
Old March 3rd, 2010, 12:39 AM   #2
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Quote:
Originally Posted by Jamie Dull View Post
...Then when I rendered it (720X480, square pixel, progressive) I ended up with thin black bars on the sides of the image...
I suspect something is wrong in this last render step.

The square-pixel 4:3 standard def size is 640x480 - try that for the last render. Does that work?

Ah, a closer look at those last settings reveals 720x480 at .909 PAR - DV. Rendering for online services is always better at 1.0PAR, the online services can do unpredictable things with non-square PAR.

Are you embedding the amazon player in a webpage in photo #3? If so, this may be related to the height of the control bar not being considered in the pixel dimensions of the embedded player. Try adding 24 pixels or so to the height param, eg. instead of
Code:
<object width="640" height="480">...
<embed ...width="640" height="480">...
You'd want:
<object width="640" height="504">...
<embed ...width="640" height="504">...
If pic #3 is a snip from an Amazon web page you won't have this control. But, getting into true square pixels may be enough to fix things.

You might also consider MP4 for the final render instead of MPEG2 - better quality for filesize, pixels are always square, IIRC.
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Old March 3rd, 2010, 03:01 PM   #3
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Quote:
Originally Posted by Jamie Dull View Post
Then when I rendered it (720X480, square pixel, progressive) I ended up with thin black bars on the sides of the image.
Of course you did. 720x480 is not 4:3. If you want a 4:3 image with 480 lines, divide 480 by 3. That gives you 160. Then multiply that by 4. That gives you 640, not 720.

The thin black bars just fill in the difference.

Alternately, if you want a 4:3 image that is 720 wide, divide 720 by 4 (=180) and multiply by 3. You will get 540. So, 640x480 is 4:3, 720x540 is 4:3 (though not standard). But 720x480 is not 4:3, it is 3:2.
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Old March 3rd, 2010, 11:23 PM   #4
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Problem Solved

Thanks for the responses. I feel kinda stupid now. 640X480 did the trick. The video above is actually on YouTube not Amazon. Seth, I know what you mean about adding pixels for the control bar. I've had to do that before when embedding videos on my blog.
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Old March 4th, 2010, 01:19 AM   #5
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Quote:
Originally Posted by Adam Stanislav View Post
720x480 is not 4:3.
Actually, yes it is. Your example only holds true in the world of square pixels on a computer. In the world of SD television, the pixels are not square. So 720x480 *IS* 4:3. Not coincidentally, if you are working in SQUARE pixels on a computer with the idea of taking it to NTSC broadcast (like a DVD), then you need to use 655x480. NTSC uses a PAR of .9091. So a square pixel image 655 pixels wide / .9091 = 720.45 And fits nicely in the 720x480/4:3 space of broadcast TV. If you tried to use 640 as your width when going to TV then 640 / .9091 = 704. And that leaves black bars on the sides of the screen 8 pixels wide each.

While this may seem confusing, it's even worse to offer unintended misinformation that might cause problems down the road. Might as well give the full explanation up front and let folks know that what mathematically might work out as 4:3 isn't what is always called 4:3.

Fortunately, this is all greatly simplified in the world of HDTV since it uses square pixels just like computers do.
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Old March 4th, 2010, 09:15 AM   #6
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Originally Posted by Perrone Ford View Post
Your example only holds true in the world of square pixels on a computer.
Which is exactly what we were talking about. Uploading a video to a web site. Web sites use computer files with square pixels.
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Old March 4th, 2010, 10:06 AM   #7
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Originally Posted by Adam Stanislav View Post
Which is exactly what we were talking about. Uploading a video to a web site. Web sites use computer files with square pixels.
Right... but declaring 720x480 is not 4:3 with no explanation really can confuse people down the road. That's all I was saying.
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