"Transcode failed"

Hi! I set up Bevy on a server with ffmpeg installed, but when I try to play something I get "The media could not be loaded, either because the server or network failed or because the format is not supported." in the browser. If I CURL the request I see this:

```
{"error":true,"message":"Transcoding failed"}
```

The weird thing is that if I call ffmpeg myself with something like this
```bash
ffmpeg -ss 00:00:00 -i http://domain:8086/v1/torrents/torrent/hash/stream/0 -f ismv -c:v libx264 -c:a libmp3lame -maxrate 1G -vf scale=iw:ih -threads 0 -preset veryfast -tune zerolatency -map 0:v:0 -map 0:a:0 -movflags frag_keyframe+empty_moov testfile
```

it works. What am I missing? Thanks!