淡入淡出Fade

淡入淡出是让声音或画面从无到有、从有到无的过渡。

• 音频淡入：音量从 0 逐渐升到正常，常用于音乐或音效的开头，避免「啪」的一声。
• 音频淡出：结尾音量逐渐降为 0。
• 在片段开头或结尾拖出一个小三角手柄，即可快速添加音频淡入淡出；时长可以拖动调整。

A fade makes audio or video appear from nothing or disappear into nothing.

• Audio fade-in: volume rises from 0 to normal, commonly used at the start of music or effects to avoid a sudden "pop".
• Audio fade-out: volume drops to 0 at the end.
• Drag a small triangle handle at the start or end of a clip to add an audio fade quickly; drag to adjust the duration.