[Google Chromecast] Asphyx:
I'll try and paste the answer from our PM so the rest of the folks can benefit...

Hit or Miss (depending on the video format) but the answer is probably not. When using aVia the Plex server can't transcode for CCast as it doesn't even know it exists.What Transcoding Plex might use (if any) when aVia requests a stream is unclear since there is no profile specifically for the aVia (profiles are usually for devices not software and it is up to the software to identify what it needs which may not be the case with aVia).

Transcoding may or may not happen and even when it does happen what it transcodes to varies from device to device. Only when the App making the request identifies itself as THIS TYPE OF DEVICE (or Profile) will Plex know how to transcode for it and do so. aVia Devs could probably solve this problem at some point so all of what I'm saying could change if they wanted it to.

YES! Plex for Android and Plex for PlexPass will both play files that are not chromecast compatible and transcode them for playback on the CCast, but there will probably be some exception to that from time to time where a file doesn't transcode so easily, or the Plex Transcoder itself doesn't like the file.

The difference is in how the two methods approach playback on the CCast.

Plex treats the CCast like a DLNA player and the Plex Apps don't ever actually play the video itself they merely tell the CCast to get it directly from the Server which makes the Server use the CCast Transcoding profile and rules.

aVia acts as a sort of Middleman where it gets the data and then forwards it to the CCast.(Note this is best Guess not CERTAIN by any means only aVia devs know for sure!) This means the server has no idea the CCast is being used and sends what stream it thinks the aVia can handle (which may not be compatible with CCast.)

Method 1 (Plex) - You pick a file in PlexApp and tell it to cast it, Plex app sends a command to CCast to go get the file from the server. Server transcodes for CCast and the file plays directly on CCast

Method 2 (aVia) - You pick a file in aVia and tell it to cast it, aVia tells the server to send it to aVia then aVia sends the data to the CCast.

Best combination right now for streaming Plex Server (and incompatible) content to CCast are the Plex apps...If Plex Server can recognize the file it should transcode properly for CCast.

Unfortunately (as we speak) to use the Plex apps with CCast requires a PlexPass account (Not free). This is only temporary and it will not be required in the near future.

So if money is not a big issue I suggest trying it for a month by getting a month of PlexPass and giving it a good test run. Hopefully by the time that Month is done PlexPass will no longer be required to stream to CCast after that.

Just to be a little clearer on when and how transcoding happens...

The PLAYER is the key to transcode/Not Transcode and is the one responsible for communicating to the Plex Server what it requires as far as transcoding is concerned. It is the player communicating with the server that tells Plex Server which profile to use when the player makes a request to get the file.

In the Plex System the Player resides on and is written FOR the CCast and it tells the Plex server it is a CCast.

In aVia it is unclear what the aVia player tells the Plex server or that it gives PlexServer any information about itself or it's intentions of what it plans to do with the file at all.

Without any information about it's target Plex server may not do any transcoding or if minimal information is given during the file request it may use a generic profile which may not be as compatible with CCast as lets say a Android profile might be.

And let me be clear (and Fair to the aVia Devs). We are just GUESSING based on observations on how aVia seems to be working in conjunction with CCast. The best place to get answers (and solutions as well) is to ask these questions regarding aVia on their support site (if they have one).

Not only will they be much more informed at how their app works but your Question may even lead them to change or update their code to work much better in a transcoding environment where casting to CCast is concerned.

They may already be working on these things, or we could be totally off base in how aVia is doing what it does.

And I don't want to give the impression that aVia is doing something wrong or that Plex is better for anything other than streaming from PlexServer at the moment.

aVia does many things the Plex Apps will NOT DO such as casting Local ON UNIT files that PlexApps simply doesn't do.

And other than the temporary requirement of needing a PlexPass to cast to CCast with Plex, In the end having BOTH APPS (aVia and Plex) will make a very Versatile and Complementary tandem to stream any kind of local content (be it Plex Server or ON UNIT) to the CCast.