CicadaPlayer播放mp4多音轨视频时，怎么切换不同音轨？

**Describe the bug**
A clear and concise description of what the bug is.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

**Expected behavior**
A clear and concise description of what you expected to happen.

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Desktop (please complete the following information):**
- OS: [e.g. iOS]
- Browser [e.g. chrome, safari]
- Version [e.g. 22]

**Smartphone (please complete the following information):**
- Device: [e.g. iPhone6]
- OS: [e.g. iOS8.1]
- Browser [e.g. stock browser, safari]
- Version [e.g. 22]

**Additional context**
Add any other context about the problem here.

The issue does not identify a source file, test, platform, browser, or reproducible steps. First inspect CicadaPlayer's audio-track selection entry points and reproduce playback of an MP4 with multiple audio tracks; done means documenting or implementing a confirmed way to switch tracks.

Written by the indexing model from the issue text.