7.5.5 Use case: High Efficiency Video Coding (HEVC)

% Just a suggestion!
% I assume that my translations have been thoroughly checked by a
% native speaker and, if necessary, corrected.
% Whether you keep the internal comments/o-text is up to you. Of course!

An example of video profile based on CRF, a quality-controlled
variable bitrate, instead of fixed quality scale (VBR).

% HEVC (H.264) wurde als Nachfolger von AVC (H.264) entwickelt, um
% die zukünftig aufkommenden große Datenmengen von 2/4/8k Videos
% effizienter zu komprimieren.
HEVC (H.264) was developed as a successor to AVC (H.264) to more
efficiently compress the future large amounts of data from 2/4/8k
videos.
%
% Im Vergleich zu AVC kann von einer durchschnittlichen Einsparung
% von rund 30 Prozent ausgegangen werden, bei gleiche Qualität.
In comparison to AVC, an average saving of around 30 percent can be
assumed for the same quality.
%
% Weil HEVC an kein Größen-Format gebunden ist, eignet es sich
% faktisch für jede Bildgröße.
Because HEVC is not bound to any size format, it is suitable for
virtually any image size.
%
% Das folgende Beispiel ist auf HD und FullHD ausgerichtet und
% erzeugt eine mit Abstrichen der Blu-ray ähnliche Bildqualität.
The following example is HD and FullHD oriented and produces a
picture quality similar to the Blu-ray with some limitations.
%
% Als Container wird Matroska (.mkv) verwendet, aber auch mp4 und
% weitere sind möglich.
As container Matroska (.mkv) is used, but also mp4 and others are
possible.

% Internel notes:
% The purpose of the comments in the profile is, on the one hand, to
% provide the user with a description if he copies it and creates a
% profile of it. On the other hand, it supports readability. If you
% tear them apart and attach them to the bottom of the page as a
% note, possibly with two pages, the eye is overwhelmed. So he gets
% used to the formatting of the profiles and sees that it is not
% witchcraft.
%
% The first line determines the container followed by the codec.

\begin{lstlisting}
matroska libx265

# CRF 16 creates a balanced compromise
# between quality and file size. 
crf=16

# Preset changes encoding speed and generally
# degrades the overall result. Medium (default)
# always fits.
preset=medium

# Additional parameters that are passed on to the codec.
# me=star improves the search for very fast
# movements, but slows down the encoding.
#x265-params=me=star

# Keyint does FFmpeg automatically, otherwise
# the setting must match the frame rate.
#keyint_min=25

# Profile does FFmpeg automatically.
#profile=high

# Source sRBG and retention of color space.
# 720/1080=bt709 if no profile set. Useful
# for formats smaller than 720 if no lossy
# conversion is desired.
colorspace=bt709
color_trc=bt709
color_primaries=bt709

# Output in 10 bit, prevents 8-bit step formation
pixel_format=yuv420p10
\end{lstlisting}

NOTE:

A CRF of 16 delivers satisfactory results in most cases. However, if
the video material is really \emph{grainy},
% grainy, see "x265 Presets/Tuning"
a CRF~16 can lead to unwanted large files.  In this case, a trial
export of perhaps one minute should be performed. The resulting bit
rate can be used to correct the CRF to 17,\,18,\,19\ldots ---
remember, a CRF of 0 means lossless, the higher the number the
stronger the lossy compression. The approximate calculation of the
final file size can be extrapolated from the sample export.

The color space information must be used explicitly so that it can
be included in the video. Cinelerra\,GG or FFmpeg does not write it
by itself. Without this information the players
(e.\,g.\ \href{https://mpv.io/}{mpv}) stick to the dimensions of the
video and take the assumed color model from a table.
%
For videos from 720 to 1080, this is bt709. 
%
For smaller dimensions, e.\,g.\ DVD, bt601 is assumed and for 4k and
above it is bt2020. Normally this is not a problem, but if you want
to export a FullHD without color loss to a smaller size like 576 for
example, you have to inform the encoder as well as the decoder of
the player. This also applies if the videos are to be loaded on
video platforms, where they are then converted into videos of
different sizes. It is a security measure to prevent false colors,
such as the color profiles in digital photos and the copies made
from them.

% Das HEVC Tuning wurde an dieser Stelle nicht berücksichtigt, weil
% es nur selten gebraucht wird und Hintergrundwissen erfordert. 
The HEVC tuning has not been considered here, because it is is
rarely used and requires background knowledge.

% Weiterführende Links
Further links:
\begin{itemize}
\item \href{http://x265.readthedocs.org/en/default/}{x265
    Documentation}
\item \href{http://x265.readthedocs.org/en/latest/cli.html}{x265
    Command Line Options}
\item \href{http://x265.readthedocs.org/en/latest/presets.html}{x265
    Presets/Tuning}
\end{itemize}