moov（Movie Box）

Movie Box，存储 mp4 的 metadata，一般位于mp4文件的开头。

The metadata for a presentation is stored in the single Movie Box which occurs at the top-level of a file. Normally this box is close to the beginning or end of the file, though this is not required.

mvhd：Movie Header Box，mp4文件的整体信息，比如创建时间、文件时长等；

trak：Track Box，一个mp4可以包含一个或多个轨道（比如视频轨道、音频轨道），轨道相关的信息就在trak里。trak是container box，至少包含两个box，tkhd、mdia；

⚠️

mvhd针对整个影片，tkhd针对单个track，mdhd针对媒体，vmhd针对视频，smhd针对音频，可以认为是从宽泛 > 具体，前者一般是从后者推导出来的。


use crate::atoms::{mvex::MvexBox, mvhd::MvhdBox, trak::TrakBox};
use crate::atoms::{BoxType, HEADER_SIZE};

#[derive(Debug, Clone, PartialEq, Default)]
pub struct MoovBox {
    pub mvhd: MvhdBox,

    pub mvex: Option<MvexBox>,

    pub traks: Vec<TrakBox>,
}

impl MoovBox {
    pub fn get_type(&self) -> BoxType {
        BoxType::MoovBox
    }

    pub fn get_size(&self) -> u64 {
        let mut size = HEADER_SIZE + self.mvhd.box_size();
        for trak in self.traks.iter() {
            size += trak.box_size();
        }
        size
    }
}