Flutter Social Media App Call Quality Optimization

I have a Flutter social media app where I've noticed some significant call quality issues. This problem is not limited to Android devices; it affects all devices, but interestingly, it is not present in iOS. I'm looking for an expert who can optimize both the server and the app code to improve the call quality.

Key aspects of the project include:
- The primary goal is to optimize the calls for improved quality. This is the most important aspect of the project.
- The issue exists across all types of devices, not just on Android, and currently does not affect iOS devices.
- I'm looking for a professional who can address this issue by optimizing both the server and the app code.

Your ideal skills:
- Proficient in working with Flutter for social media apps
- Expertise in server optimization
- Strong background in app code optimization

Your responsibilities:
- Identify the root cause of the call quality issue and propose a workable solution
- Implement the necessary optimizations in both the server and app code
- Ensure that the call quality is significantly improved across all types of devices

Please provide examples of similar projects you've worked on in the past.

Yii backend