[Streaming]: Playing multiple return audio streams not working
### Streaming Issue

Ok, this is probably me, but I'm attempting to play return audio out the camera speaker twice. The goal is to play one sound file, then another. I've tried a couple of different approaches to this. Both are based off the return audio example.

I create a new RtpSplitter and FfmpegProcess to play the sound back out the actively streaming video stream. This successfully plays the audio out the camera.

In one approach I then reuse the RtpSplitter but create a new FfmpegProcess to play the second sound file. In another approach I close the original RtpSplitter and create a new RtpSplitter in order to play the second file.

In both scenarios the sound file plays the first time, but the second file does not play. When I restart the inbound live stream from the camera I can again play the sound file, one time.

The log output from both outbound processes appears the same.

### Proposed Solution

Unsure. Can anyone offer guidance on how I might need to adjust my playing to allow both audio files to play, one after the other (with a bit of a gap)?

### Environment

Other (ring-client-api)

### What operating system are you on?

Mac

### Relevant log output

```shell
INFO [2021-08-19 21:45:24.111 +0000] (4059 on macbook-pro.lan): Return Audio 1: [mp3 @ 0x7fc6df00b600] Estimating duration from bitrate, this may be inaccurate
Input #0, mp3, from '/Users/david/src/core/packages/apps/robotzero/media/identify.mp3':
  Metadata:
    encoder         : Lavf58.76.100
  Duration: 00:00:01.37, start: 0.000000, bitrate: 48 kb/s
    Stream #0:0: Audio: mp3, 24000 Hz, mono, fltp, 48 kb/s

    module: "ring"
INFO [2021-08-19 21:45:24.116 +0000] (4059 on macbook-pro.lan): Return Audio 1: Stream mapping:
  Stream #0:0 -> #0:0 (mp3 (mp3float) -> pcm_mulaw (native))
Press [q] to stop, [?] for help

    module: "ring"
INFO [2021-08-19 21:45:24.119 +0000] (4059 on macbook-pro.lan): Return Audio 1: Output #0, rtp, to 'srtp://127.0.0.1:52758?pkt_size=188':
  Metadata:
    encoder         : Lavf58.45.100

    module: "ring"
INFO [2021-08-19 21:45:24.120 +0000] (4059 on macbook-pro.lan): Return Audio 1:     Stream #0:0: Audio: pcm_mulaw, 8000 Hz, mono, s16, 64 kb/s
    Metadata:
      encoder         : Lavc58.91.100 pcm_mulaw

    module: "ring"
INFO [2021-08-19 21:45:24.618 +0000] (4059 on macbook-pro.lan): Return Audio 1: size=       4kB time=00:00:00.50 bitrate=  72.5kbits/s speed=0.999x    
    module: "ring"
INFO [2021-08-19 21:45:25.120 +0000] (4059 on macbook-pro.lan): Return Audio 1: size=       9kB time=00:00:01.00 bitrate=  72.2kbits/s speed=   1x    
    module: "ring"
INFO [2021-08-19 21:45:25.492 +0000] (4059 on macbook-pro.lan): Return Audio 1: size=      12kB time=00:00:01.36 bitrate=  72.2kbits/s speed=0.997x    
video:0kB audio:11kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 12.865497%

    module: "ring"
INFO [2021-08-19 21:45:25.494 +0000] (4059 on macbook-pro.lan): Return Audio 1: stopped gracefully
    module: "ring"
INFO [2021-08-19 21:45:43.347 +0000] (4059 on macbook-pro.lan): Return Audio 2: [mp3 @ 0x7fc57c80b600] Estimating duration from bitrate, this may be inaccurate

    module: "ring"
INFO [2021-08-19 21:45:43.348 +0000] (4059 on macbook-pro.lan): Return Audio 2: Input #0, mp3, from '/Users/david/src/core/packages/apps/robotzero/media/identify.mp3':
  Metadata:
    encoder         : Lavf58.76.100
  Duration: 00:00:01.37, start: 0.000000, bitrate: 48 kb/s
    Stream #0:0: Audio: mp3, 24000 Hz, mono, fltp, 48 kb/s

    module: "ring"
INFO [2021-08-19 21:45:43.349 +0000] (4059 on macbook-pro.lan): Return Audio 2: Stream mapping:
  Stream #0:0 -> #0:0 (mp3 (mp3float) -> pcm_mulaw (native))
Press [q] to stop, [?] for help

    module: "ring"
INFO [2021-08-19 21:45:43.350 +0000] (4059 on macbook-pro.lan): Return Audio 2: Output #0, rtp, to 'srtp://127.0.0.1:52758?pkt_size=188':
  Metadata:
    encoder         : Lavf58.45.100

    module: "ring"
INFO [2021-08-19 21:45:43.352 +0000] (4059 on macbook-pro.lan): Return Audio 2:     Stream #0:0: Audio: pcm_mulaw, 8000 Hz, mono, s16, 64 kb/s
    Metadata:
      encoder         : Lavc58.91.100 pcm_mulaw

    module: "ring"
INFO [2021-08-19 21:45:43.850 +0000] (4059 on macbook-pro.lan): Return Audio 2: size=       4kB time=00:00:00.50 bitrate=  72.5kbits/s speed=   1x    
    module: "ring"
INFO [2021-08-19 21:45:44.353 +0000] (4059 on macbook-pro.lan): Return Audio 2: size=       9kB time=00:00:01.00 bitrate=  72.2kbits/s speed=   1x    
    module: "ring"
INFO [2021-08-19 21:45:44.725 +0000] (4059 on macbook-pro.lan): Return Audio 2: size=      12kB time=00:00:01.36 bitrate=  72.2kbits/s speed=0.994x    
video:0kB audio:11kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 12.865497%

    module: "ring"
INFO [2021-08-19 21:45:44.728 +0000] (4059 on macbook-pro.lan): Return Audio 2: stopped gracefully
    module: "ring"
```


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