[FFmpeg-user] Glossary: Nyquist

[Eduardo Alarcón]

Nyquist is a noun, not an adjective, for Harry Nyquist. The Nyquist–Shannon
sampling theorem is applicable to analog to digital conversion of signals
(continuous to discrete), images are a type of signal.

El mié., 30 sept. 2020 a las 20:25, Mark Filipak (ffmpeg) (<
markfilipak at bog.us>) escribió:

> 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
>
> --
> What if you woke up and found yourself in a police state?
> African-Americans wake up in a police state every day.
> _______________________________________________
> ffmpeg-user mailing list
> ffmpeg-user at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-user
>
> To unsubscribe, visit link above, or email
> ffmpeg-user-request at ffmpeg.org with subject "unsubscribe".