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    Re-encode video (using ffmpeg and libx264).

    This utility runs *ffmpeg* to re-encode your video files using the
    libx264 codec. It is a wrapper to simplify invocation of ffmpeg. It
    selects the appropriate ffmpeg options for you, allows you to specify
    multiple files, and picks appropriate output filenames. It also sports a
    "--dry-run" option to let you see ffmpeg options to be used without
    actually running ffmpeg.

    This utility is usually used to reduce the file size (and optionally
    video width/height) of videos so they are smaller, while minimizing
    quality loss. Smartphone-produced videos are often high bitrate (e.g.
    >10-20Mbit) and not yet well compressed, so they make a good input for
    this utility. The default setting is roughly similar to how Google
    Photos encodes videos (max 1080p).

    The default settings are:

     -v:c libx264
     -preset veryslow (to get the best compression rate, but with the slowest encoding time)
     -crf 28 (0-51, subjectively sane is 18-28, 18 ~ visually lossless, 28 ~ visually acceptable)

    when a downsizing is requested (using the "--downsize-to" option), this
    utility first checks each input video if it is indeed larger than the
    requested final size. If it is, then the "-vf scale" option is added.
    This utility also calculates a valid size for ffmpeg, since using "-vf
    scale=-1:720" sometimes results in failure due to odd number.

    Audio streams are copied, not re-encoded.

    Output filenames are:

     ORIGINAL_NAME.crf28.mp4

    or (if downsizing is done):

     ORIGINAL_NAME.480p-crf28.mp4

    This function is not exported.

    This function supports dry-run operation.

    Arguments ('*' denotes required arguments):

    *   audio_sample_rate => *uint*

        Set audio sample rate, in Hz.

    *   crf => *int*

        (No description)

    *   ffmpeg_path => *filename*

        (No description)

    *   files* => *array[filename]*

        (No description)

    *   frame_rate => *ufloat*

        Set frame rate, in fps.

    *   overwrite => *bool*

        (No description)

    *   preset => *str* (default: "veryslow")

        (No description)

    *   scale => *str* (default: "1080^>")

        Scale video to specified size. See Math::Image::CalcResized or
        calc-image-resized-size for more details on scale specification.
        Some examples include:

        The default is "1080^>" which means to shrink to 1080p if video size
        is larger than 1080p.

        To disable scaling, set "--scale" to '' (empty string), or specify
        "--dont-scale" on the CLI.

    Special arguments:

    *   -dry_run => *bool*

        Pass -dry_run=>1 to enable simulation mode.

    Returns an enveloped result (an array).

    First element ($status_code) is an integer containing HTTP-like status
    code (200 means OK, 4xx caller error, 5xx function error). Second
    element ($reason) is a string containing error message, or something
    like "OK" if status is 200. Third element ($payload) is the actual
    result, but usually not present when enveloped result is an error
    response ($status_code is not 2xx). Fourth element (%result_meta) is
    called result metadata and is optional, a hash that contains extra
    information, much like how HTTP response headers provide additional
    metadata.

    Return value: (any)

  split_video_by_duration
    Usage:

     split_video_by_duration(%args) -> [$status_code, $reason, $payload, \%result_meta]

    Split video by duration into parts.

    This utility uses ffmpeg (particularly the "-t" and "-ss") option to
    split a longer video into shorter videos. For example, if you have
    "long.mp4" with duration of 1h12m and you run it through this utility
    with "--every 15min" then you will have 5 new video files:
    "long.1of5.mp4" (15min), "long.2of5.mp4" (15min), "long.3of5.mp4"
    (15min), "long.4of5.mp4" (15min), and "long.5of5.mp4" (12min).

    Compared to using "ffmpeg" directly, this wrapper offers convenience of
    calculating the times ("-ss") option for you, handling multiple files,
    automatically choosing output filename, and tab completion.

    This function is not exported.