Voice/Video Conference Wishlist

Here are a bunch of things that I would like to see support for in conferencing, in order to support different uses.

- [ ] ability to join a conference as a passive participant (not sending any voice or video -- is this already possible?)
- [ ] require a certain power level to speak (e.g. for online presentations/lectures, where generally only the presenter speaks, but can also allow others to speak when needed, such as for asking questions)
- [ ] require a certain power level to send in video
- [ ] have an indicator for who is speaking (e.g. having a "foo is speaking" line in the status bar, similar to the typing indicator)
- [ ] allow moderators to mute people (telling a user's client to mute itself -- this is mainly intended as a convenience function (e.g. person has stepped away from their device and a baby starts crying loudly) and can be overridden by the user)
- [ ] persistent conferences (conferences that don't disappear when the last person leaves)
- [ ] require a certain power level to start a conference
- [ ] ability to upload a pdf/odp/ppt/etc. and use it as your "video" e.g. for presenting slides in online presentations (the same effect could be obtained by screen-sharing a viewer program, but by uploading a file and signalling to clients which slide to view, you would get both better quality and lower bandwidth usage)
- [ ] option to auto-enter a voice/video conference (as a listener or as a participant) when clicking on a room (so you don't have to click the voice or video button to join)

Additional suggestions from the comments below:

- [ ] ability to invite others by sending them a link without requiring a Matrix account (similar to meet.jit.si or appear.in)
- [ ] allow controlling the volume of each speaker
- [ ] push-to-talk
- [ ] send-to-voice-detection
- [ ] adaptive bandwidth management
- [ ] ability to send multiple streams from a single client (e.g. screen sharing and webcam)