Unable to use ffmpeg.run on rtsp input stream

**Describe the bug**
Unable to use `ffmpeg.run` to use rtsp stream as the input, and output the transcoded stream over an http stream using mpeg1video encoding.
In `ffmpeg`, I can do the following
```bash
ffmpeg -i rtsp://192.168.0.101/av0_1 -f mpegts -codec:v mpeg1video -b 800k -r 30 http://localhost:8081/password
```
However, when I try doing the same thing using ffmpeg.wasm, I get the following:
```
[info] load ffmpeg-core
[info] ffmpeg-core loaded
starting
[info] ffmpeg command: ./ffmpeg -nostdin -hide_banner -i rtsp://192.168.0.101/av0_1 -f mpegts -codec:v mpeg1video -b 800k -r 30 http://localhost:8081/password
[ffmpeg-stdout] Assertion failed: undefined
[ffmpeg-stderr] Assertion failed: undefined
[ffmpeg-stdout] RuntimeError: abort(Assertion failed: undefined). Build with -s ASSERTIONS=1 for more info.
[ffmpeg-stderr] RuntimeError: abort(Assertion failed: undefined). Build with -s ASSERTIONS=1 for more info.
// then prints out ffmpeg-core.js file
```

The code I used is below:
example_stream.js:
```javascript
const { createFFmpeg } = require('@ffmpeg/ffmpeg');
const ffmpeg = createFFmpeg({ log: true });
(async () => {
await ffmpeg.load();
console.log("starting");
await ffmpeg.run("-i rtsp://192.168.0.101/av0_1 -f mpegts -codec:v mpeg1video -b 800k -r 30 http://localhost:8081/password");
})();
```

**To Reproduce**
Steps to reproduce the behavior:
1. Create a new node project
2.` npm install "@ffmpeg/ffmpeg"`
3. Run code above
4. See error

**Expected behavior**
Output similar to ffmpeg terminal command:
```
eng6@eng6-ThinkPad-P50s:~$ ffmpeg -i rtsp://192.168.0.101/av0_1 -f mpegts -codec:v mpeg1video -b 800k -r 30 http://localhost:8081/password
ffmpeg version 2.8.15-0ubuntu0.16.04.1 Copyright (c) 2000-2018 the FFmpeg developers
built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.10) 20160609
...
Input #0, rtsp, from 'rtsp://192.168.0.101/av0_1':
Metadata:
title : av0_1
Duration: N/A, start: 0.034000, bitrate: N/A
Stream #0:0: Video: h264 (High), yuvj420p(pc, bt709), 1280x720, 29.97 tbr, 90k tbn, 180k tbc
Output #0, mpegts, to 'http://localhost:8081/password':
Metadata:
title : av0_1
encoder : Lavf56.40.101
Stream #0:0: Video: mpeg1video, yuv420p, 1280x720, q=2-31, 800 kb/s, 30 fps, 90k tbn, 30 tbc
Metadata:
encoder : Lavc56.60.100 mpeg1video
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> mpeg1video (native))
Press [q] to stop, [?] for help
```

**Desktop (please complete the following information):**
- OS: Ubuntu 16.04
- Browser Firefox
- Version 75
- Node version: 12.7.0
- NPM version: 6.14.5
- "@ffmpeg/ffmpeg" version: "^0.8.3",

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