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400x300 - FLV - Not right?

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Danny2007
400x300 - FLV - Not right?
on Jul 9, 2007 at 11:36:53 am

Guys

I have generally always avoided encoding to 400x300 as I don't believe it's a correct frame size, i.e not divisible by 8.

I'd rather opt for either 384x288 or 416x312.

That's said I see some many clips delivered at 400x300.

In this instance I'm specifically referring to Flash encoding (VP6)

I'd love to hear the opinions as to whether divisible by 8 is a big deal when it comes quality and efficiency, or not.

Thanks

Danny



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Evil Ash Editor
Re: 400x300 - FLV - Not right?
on Jul 10, 2007 at 6:48:36 pm

I have actually encoded to 400x300 and not noticed an issues with it. I would recommend testing it out on your footage. Also, if you're concerned with it distorting your picture, encode a video of a circle to see if the frame causes it to become elliptical.


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Danny2007
Re: 400x300 - FLV - Not right?
on Jul 11, 2007 at 10:45:30 am

Err nothing to do with PAR or frame aspect ratio (400x300 is quite obviously 4:3) but absolutely to do with what I thought were some of the basics of compression i.e. adhearing to a frame size divisable by 8x8 (or 16x16) macroblocks.

I've done my own tests and can see a difference between a non-div 8 frame size and a div 8 frame size. I just want to better understand why so many seem to be ignoring the fundimentals.

Thanks

DL





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yuzztme
Re: 400x300 - FLV - Not right?
on Oct 13, 2007 at 9:47:06 pm

I've been looking for an answer whether to use a frame width/height value which is a multiple of 8 or 16 pixels. The VP6 codec doesn't seem to have any restrictions regarding framesize. I did find out that frame width/height values are not only codec related, but also depend on the used color space.

For FLV I use the YV12 color space. Both image dimensions have to be a multiple of two, if the video is interlaced the height has to be a multiple of four.


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Danny2007
Re: 400x300 - FLV - Not right?
on Oct 14, 2007 at 9:06:22 am

I'm not sure where you've got your information from but I disagree with it.

According to On2, the makers of the VP6 CODEC used in Flash video, the frame size should ideally be equally divisible by 8 on both axis, as outlined on this page:

http://www.on2.com/support-resources/flix-tutorials/flashvideoquality/

The same can be said of pretty well all video CODECS out there, usually however it should be 16 rather than 8. Certainly not 2 or 4.

I don't understand your reference to YV12 and, did you mean YV12 as your source? - FLV is an RGB CODEC.

Lastly FLV is a progressive only format, you should deinterlace interlaced source before transcoding to FLV.


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JackHammer
Re: 400x300 - FLV - Not right?
on Oct 15, 2007 at 9:11:05 am

Danny2007 is right - frame sizes should be divisible by 8 or 16.

Here's a list of optimum sizes: http://blog.influxis.com/influxis/?p=14



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