'simulcast' - ffmpeg/gstreamer record lowest stream

[doublex]

After applying this patch, ffmpeg as well as gstreamer record the scaleResolutionDownBy: 4 stream:

diff -r app-orig/src/gum.js app/src/gum.js
<   video: { width: 640, height: 480 }
---
>   video: { width: 1280, height: 720 }

diff -r app-orig/src/index.js app/src/index.js
<     const videoProducer = await peer.sendTransport.produce({ track: videoTrack });
---
>     const videoProducer = await peer.sendTransport.produce({ track: videoTrack,
>         encodings: [
>             { maxBitrate:  96000, scaleResolutionDownBy: 4 },
>             { maxBitrate: 680000, scaleResolutionDownBy: 1 },
>         ] });

[ethand91]

This sample does not use simulcast.