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Forums Adobe Media Encoder ENCODING: Chroma/GOP/Pixel Aspect Ratio

  • ENCODING: Chroma/GOP/Pixel Aspect Ratio

  • Ben Komins

    October 17, 2014 at 12:45 am


    Can someone please point me in the right direction within Adobe Media Encoder for the following specs:

    GOP: Closed Long GOP (IBBP)
    Pixel Aspect Ratio: 9:10
    Chroma: 4:2:2 ([email protected])

  • Ivan Myles

    October 17, 2014 at 5:04 am

    MPEG2 codec with GOP settings:
    M frames: 3
    N frames: 4 for IBBPIBBPIBBP…
    Closed GOP every: 4 (or possibly a multiple of 4)

    The other settings are marked accordingly.

  • Ben Komins

    October 17, 2014 at 5:06 am

    Thanks Ivan –
    Just so I understand it a better – can you point to a resource that explains what you just wrote with details?

  • Ivan Myles

    October 17, 2014 at 5:12 am
  • Ben Komins

    October 17, 2014 at 5:15 am

    My apologies –
    I read through that earlier – and just took a second look.

    What I meant is how does your 2/4 Closed 4 recommendation = IBBP (as opposed to just leaving it at the default 3/15 Automatic GOP placement?

  • Ivan Myles

    October 17, 2014 at 5:49 am

    Sorry, I made a mistake in the previous post. Been a while since I used MPEG2. I will edit the post shortly.

    M = Number of B frames between I/P frames. For IBBP, M=3 produces a P or I-frame every third frame. The minimum is M=1, which corresponds to zero B-frames.

    N = Number of frames between I frames. N=4 produces IBBPIBBPIBBP… Setting N=15 produces IBBPBBPBBPBBPBP as a group of pictures. Your spec doesn’t state GOP length. Admittedly, 4 is pretty short, and a number about half the frame rate is more common. Setting N=15 instead of a multiple of 4 (such as N=16) just changes the last frames in the group from BBP (16) to BP (15).

  • Ben Komins

    October 17, 2014 at 5:51 am

    Copy that. That makes more sense. Many thanks.

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