transcoding

The value of allowed undershoot in the resize mode ExactOrSmaller is currently a compile time constant. It would be great to make this configurable for the developer using the library:

https://github.com/facebookincubator/spectrum/blob/fa9e917f5b062797d51c3e013aaa7d61926c72a5/cpp/spectrum/core/ResizeUtil.h#L22-L27

Not an issue as such, but is there a scope where you can make it client specific in terms of the ip address of last played the item? Instead for all clients?

At the moment, while an encoding is in progress, the encoding settings can be changed. Although I assume changing these will have no effect in the encoding in progress, it is rather odd and distracting that you can change them.

I suggest to grey these out while an encoding is in progress so they cannot be changed. I think greying is better than hiding, so you can see what settings were picked eve