VideoHelp Forum
+ Reply to Thread
Results 1 to 10 of 10
Thread
  1. Member
    Join Date
    Oct 2008
    Location
    South Africa
    Search Comp PM
    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?
    Quote Quote  
  2. DECEASED
    Join Date
    Jun 2009
    Location
    Heaven
    Search Comp PM
    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.
    Quote Quote  
  3. Member
    Join Date
    Aug 2013
    Location
    Central Germany
    Search PM
    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 2×2 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 16×16 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.
    Quote Quote  
  4. Member
    Join Date
    Oct 2008
    Location
    South Africa
    Search Comp PM
    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.
    Quote Quote  
  5. Member
    Join Date
    Aug 2013
    Location
    Central Germany
    Search PM
    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.
    Quote Quote  
  6. Member
    Join Date
    Oct 2008
    Location
    South Africa
    Search Comp PM
    623 is also odd. Wrong again.
    Typo! I meant 624.
    Quote Quote  
  7. 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.
    Quote Quote  
  8. Member
    Join Date
    Sep 2012
    Location
    Australia
    Search Comp PM
    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 16×16 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.
    Quote Quote  
  9. Video Restorer lordsmurf's Avatar
    Join Date
    Jun 2003
    Location
    dFAQ.us/lordsmurf
    Search Comp PM
    640x360 is industry standard
    only the torrent crowd does the weird SD resolutions
    Want my help? Ask here! (not via PM!)
    FAQs: Best Blank DiscsBest TBCsBest VCRs for captureRestore VHS
    Quote Quote  
  10. DECEASED
    Join Date
    Jun 2009
    Location
    Heaven
    Search Comp PM
    Some years ago, I used 624x352 because of overscan issues on my CRT TV...

    But those days are gone.
    Quote Quote  
Visit our sponsor! Try DVDFab and backup Blu-rays!