HDR10 中的max-cll max-fall 到底是什么

MaxCLL(Maximum content light level ) 表示的是视频中像素的峰值亮度 单位是cd/m2，或者nits， 目前大多数数视频会将这个参数设置为1000nit
MaxFALL(maximum frame average light level) 表示的是视频整个画面的最大平均亮度， 目前大多数数视频会将这个参数设置为400nit，由于显示屏整个屏幕全部显示1000nits 过于影响屏幕寿命， 故设置这个参数来防止整个画面过于明亮

Maximum content light level (MaxCLL) and maximum frame average light
    level (MaxFALL) as required by the Consumer Electronics Association
    861.3 specification.

    Specified as a string which is parsed when the stream header SEI are
    emitted. The string format is "%hu,%hu" where %hu are unsigned 16bit
    integers. The first value is the max content light level (or 0 if no
    maximum is indicated), the second value is the maximum picture
    average light level (or 0). Applicable for HDR content.

    Example for MaxCLL=1000 candela per square meter, MaxFALL=400
    candela per square meter: