[FFmpeg-user] Glossary: Nyquist

Greg Oliver oliver.greg at gmail.com
Thu Oct 1 19:16:41 EEST 2020

On Wed, Sep 30, 2020 at 6:25 PM Mark Filipak (ffmpeg) <markfilipak at bog.us>

> Nyquist [adjective]: 1, Reference to the Nyquist–Shannon sampling
>    theorem. 2, The principle [1] that, to most faithfully reproduce an
>    image at a given digital display's resolution, the samples must be
>    made at or above twice the display's resolution, both horizontally &
>    vertically [2].
>    [1] The Nyquist principle applies to film sampling and to digital
>        cameras, but, provided that resolution is unchanged, not to
>        transcoding (because the transcoder inputs are already digital).
>        As proved by the improved appearance of SD media made from 2K
>        samples, SD mastering prior to the advent of 2K sampling (e.g.
>        DVDs mastered before the advent of HD) generally ignored the
>        Nyquist principle and were undersampled. HDs sampled at 2K and
>        UHDs sampled at 4K are likewise undersampled.
>    [2] As a convenience, the Nyquist threshold is currently (in 2020)
>        specified solely by horizontal sample count rounded up to whole
>        kilo-samples (2K, 4K, 8K).
>                          display    Nyquist threshold
>        UHD 16:9-2160:  3840 x 2160         8K
>             4:3-2160:  2880 x 2160         8K
>         HD 16:9-1080:  1920 x 1080         4K
>             4:3-1080:  1440 x 1080         4K
>         SD  16:9-576:  1024 x 576          4K
>              4:3-576:   768 x 576          2K
>             16:9-480:   853 x 480          2K
>              4:3-480:   640 x 480          2K


Normally I would absolutely defend your queries as they are technical and
lower level, but I would almost have to side with Bouke from post
bwdif filter question

You are trying to get free editing for your book now.  I do not agree with
that..  There are many good contributors and inquisitors (you included),
but (IMHO) you cannot solicit things like this that are grammatical rather
than technical.   I think a lot of the developers are also in the same boat
as you (sometimes) try to re-define things that are common language (even
if not accurate technically).

eg - your definition if interlaced versus interweaved..  No matter if you
are right or wrong, the concept and understanding of a majority will
prevail - no exceptions.

Please (for me at least) keep your posts here related to ffmpeg and not
trying to change the nomenclature of what exists.  We are all using the
same software, so whatever the software uses for terminology (as this list
is exactly related to), please do not interfere with that.

Take that up directly with developers and let them sort it out.

On a side note - I have yet seen one of your definitions of a technology
been held up when a developer chimes in - no hard feelings, just that
industry terminology is hard to trump :)


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