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  1. Member
    Join Date: Oct 2008
    Location: South Africa
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    Strictly speaking, 16:9 is 624 by 351. But everyone seems to use 624 by 352. Is the even number better, or is it just one of those things that happen?
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  2. vanished El Heggunte's Avatar
    Join Date: Jun 2009
    Location: Misplaced Childhood
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    It's a matter of the color space(s) supported by the "well-known" lossy video codecs.
    YV12 and YUY2 require that the width or/and the height of the frame are divisible by 2 or by 4.
    Besides, the MPEG-2 encoders require that the frame dimensions are divisible by 8.
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  3. Member
    Join Date: Aug 2013
    Location: Central Germany
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    Never use odd dimensions for videos. The most common chroma subsampling for modern video formats is YUV 4:2:0, which means that a square of each 22 pixels (which all have a distinct luminance) shares the same chrominance (blue-yellow difference and red-green difference from grey). If it is an interlaced format, the chrominance would even be shared for two lines of each field field, therefore the height would have to be a multiple of 4 even to make sense.

    On top of that, many formats (e.g. MPEG-1, MPEG-2, MPEG-4 Part 2) used to partition the video into macroblocks which are 1616 pixel squares large. Using multiples of 16 for both width and height is not necessary anymore, but still convenient, at least.

    Some decoders were also optimized for widths being multiples of 4, to use memory blocks, CPU registers, and SIMD instructions efficiently. They may introduce e.g. green stripes if that is not the case.
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  4. Member
    Join Date: Oct 2008
    Location: South Africa
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    YV12 and YUY2 require that the width or/and the height of the frame are divisible by 2 or by 4.
    Well, dividing by 4 is not always possible with a ratio such as 16:9, but at least dividing by 2 can be done.
    Will use 623x352 in future.
    I think I will use a new thread for my other question.
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  5. Member
    Join Date: Aug 2013
    Location: Central Germany
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    623 is also odd. Wrong again.

    It is not necessary to get as close as possible to 16:9. You will hardly notice four lines more or less.

    Furthermore, I don't know why "everyone seems to use 624". Who is everyone? Not me.
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  6. Member
    Join Date: Oct 2008
    Location: South Africa
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    623 is also odd. Wrong again.
    Typo! I meant 624.
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  7. Member
    Join Date: Jun 2012
    Location: USA
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    Originally Posted by NDMMackay View Post
    Well, dividing by 4 is not always possible with a ratio such as 16:9.
    640x360 is dandy for client screeners.
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  8. Member
    Join Date: Sep 2012
    Location: Australia
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    Originally Posted by LigH.de View Post
    On top of that, many formats (e.g. MPEG-1, MPEG-2, MPEG-4 Part 2) used to partition the video into macroblocks which are 1616 pixel squares large. Using multiples of 16 for both width and height is not necessary anymore, but still convenient, at least.
    Used to? It's fundamental to compression, and aint changing any time soon. All that's changed (or not changed) is that they add padding, repetition of the last scan line, which gets cropped off after decoding. I did a test a year or two ago using handbrake and an episode of Get Smart. The Mod16 version compressed better than the off-cropped version, but that may have been helped by the resize making it a tad softer. Video Encoding is generally about what you're happy with, and I think it's nice to have all my encodes at the same resolution.
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  9. Video Restorer lordsmurf's Avatar
    Join Date: Jun 2003
    Location: dFAQ.us/lordsmurf
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    640x360 is industry standard
    only the torrent crowd does the weird SD resolutions
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  10. vanished El Heggunte's Avatar
    Join Date: Jun 2009
    Location: Misplaced Childhood
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    Some years ago, I used 624x352 because of overscan issues on my CRT TV...

    But those days are gone.
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