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A
A.I.1
Legend
October 18, 2017
Question

In Adobe Media Encoder is there a way to match the source frame rate if it isn't in the list?

  • October 18, 2017
  • 1 reply
  • 16162 views

On rendering with Adobe Media Encoder, from an After Effects project which uses a 20.0 fps frame rate (there are other videos from the client that also use non-standard frame rates that I colud have chosen), Media Encoder with "Match Source" selected puts the frame rate at 23.976 fps instead of 20.0 fps (the actual source frame rate). Note: I am rendering to the H264 codec.

1) Why does Adobe Media Encoder not match the source frame rate in this case? It says "values may be constrained by the output format" but as far as I know, there is nothing about the H264 codec that limits it to just what Media Encoder has in it's very limited list box of 12 frame rates. Note. 20.0 fps isn't in the list box. Nor are other frame rates which I have also wanted to use. What if I want to use any frame rate from eg. 5.0 fps to 120.0 fps for outputting with H264? Note: The original source video the client sent is AVC (same as H264) High@L3.1, 20.0 fps.

2) Is there any way to make Media Encoder use the correct frame rate for this project (20.0 fps) instead of 23.976 (which will surely lower the quality).

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    1 reply

    W
    Community Expert
    Warren Heaton10841144Community Expert
    Community Expert
    October 19, 2017

    No, there is not a way to match a frame rate that is not in the list.  You can only pick from the ones that appear in the pop-up menu.

    If you happen to be running macOS, you can render to QuickTime Photo-JPEG at best at pretty much any frame rate you want (including 20 fps).  Then, open that file in QuickTime Player X and export to 1080p (or any of the other sizes like 720p and down).  The resulting file will be H264 at 20fps.  You can change the .mov extension to .mp4 as well.

    I'm have to ask:  With several well established frame rate standards, how did you wind up with 20 frames per second?   Granted, I get that there are some interesting numbers out there (like 7.5 GPS for Real Video in the 1990s), but lower frame rates are almost always multiples of the standard rates (so, 10, 12, 15).

    W
    Community Expert
    Warren Heaton10841144Community Expert
    Community Expert
    October 19, 2017

    Some formats do allow you to set whatever frame rate you'd like (QuickTime being the best example that I know of, assuming you've chosen a CODeC that allows it).

    Most other formats are standardized with specifications that must be adhered to.  It's what guarantees that you can go from source footage settings, to edit settings, to edited master settings to delivery settings and have files that play as expected.  Going against that is "out of spec".  For example, DV-NTSC can only run at 29.97 or 25.  There's a 24p variation, but it has 3:2 pulldown while on DV tape and can only be removed/pulled up on the computer.  If going back to tape, 3:2 pulldown had to be put back so that it's running at 29.97 again.  DVD-Video is about the same.  If at any point in a workflow an out of spec frame rate is introduced, then the footage cannot be recorded back to DV tape or the duplicated/replicated DVD-Video title will not play as expected in a DVD-Video player.

    The common numbers of 24, 30 and 25 are based on analog formats and the frame rates available in AME's pop-up menu are based on those numbers as well (most being some variation of those).  These and their variations were established for things like picture playing in sync while interlocked with audio, timing a program accurately to the hour, keeping color in phase, functioning with power systems (60Hz, 50Hz).  (I'm sure there's more that I'm not listing.)

    If a client is giving you out of spec files, it's common to bill for the time it takes to remaster/conform the footage.  If it's a really "good" client, you could list the time it takes to conform the footage on your invoice as "no charge".  Although, one could argue that a good producer would go with format standards, including frame rate.

    After Effects will allow you to enter pretty much any frame rate you want.  It used to be capped at 99, but is now 999; however, that's for flexibility with temporal resolution while in After Effects only.

    Getting back to specifications, some CODECs have strict frame rate requirements while others do not.  There's usually a white paper available by whomever published the CODEC that details this.

      A
      A.I.1Author
      Legend
      October 19, 2017

      Thanks. I was wrong about the max frame rate for After Effects (ie. it being now 999 fps not 120 fps, at least in CC 2017 - I assume it's the same in CC 2018). I looked at the max in the list box which was 120 fps. Though there are still consumer(ish) cameras that allow frame rates of 1000 fps etc.

      I'm looking at the H264 specs (on itu.int) and I only see maximum frame rates depending on various luma widths and heights and H264 levels (eg. for 4Kx2K at level 5.1, max fps is 30.0 fps. (I thought it was higher but maybe that's H265).

      But for H264, according to that document the frame rate seems to be represented by "time_scale" (eg. 30,000) and "num_units_in_tick" (eg. 1001), eg.  30,000/1001=approx 29.9700299... fps. So it seems you can set those two variables (time_scale and num_units_in_tick) to any reasonable number to represent any frame rate up to the maximum frame rate depending on the H264 level and width & height in luma samples. eg. if it's progressive I don't see why any reasonable frame rate can't be used. ie. there's nothing limiting it to the specific ones chosen in Adobe Media Encoder - if it can be represented by those two integer variables (and within certain limits, depending on the H264 level etc.) it should be okay.

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