What digital format

The 312 can stream over DLNA with either the plex server or with readydlna. Plex might be a better choice, as it will give you some on-the-fly transcoding (limited by the 312 CPU - probably not up to 1080p down-conversion).

Some clients and players can use other protocols - my media players can directly SMB/CIFS and NFS shares, and my IOS app (AVPlayer HD) can access via FTP.

As far as over-the-internet playback, the FTP approach can work (with port forwarding), or you can use something like bittorrent sync to upload to the mobile devices. You can also use ReadyNAS Remote (though its performance tends to be very uneven).

Apart from the plex transcoding and bittorrent sync, this can also be done with your duo v1.

Pretty much everything handles H264 natively at this point.

I don't know where you live but internet connection is required to stream and internet providers tend to limit the upload. if you have an ADSL connection don't think about streaming a film, 120kbytes/s at best in upload won't be enough if you want to stream surround along with a correct video quality.

buzz player can read AFP/SMB/HTTP (webdav)/FTP/DLNA on IOS too, that's why vlc on IOS is not even installed here ;)
Like it was said acessing a NAS from the internet is a matter of firewall (allow traffic from outside) and NAT (guide traffic to the right device) configuration.

I'm pretty sure handbrake can do MKV, but I remember it lacked some batch management for file to file conversion (but since it's disk to file, you will have to switch the optical disks anyway), but as said before, I haven't encoded for some time.

I believed you would go for RN102, now it's the 312 is it a typo or did you change your mind ? The difference being mainly in the transcoding power of the intel CPU and the HDMI port (that I don't know what the OS can do with).

Just checked - I have 8player installed on my iPad, not buzz. xeltros - does what version of buzz are you using? Are you sure it supports ac3 (dolby digital) surround sound playback? The current version (5.0.1) seems limited to mov and mp4 containers, and I believe it does not support ac3.

yep but AC3 is globally unavailable on IOS no ? I use buzz player HD to be precise since I'm on ipad for movies. I guess I still have an old version with ac3 somewhere but don't use it. I believed the topic author would use AC3 for home and MP3 for ipad.
For the format, mine reads mkv, the app store description lists the formats read.

The web site for buzz wasn't complete, I didn't think to check the store.

avplayerhd supports ac3 on the ipad (but not DTS). I'd probably use aac for the stereo codec, not mp3.

Ah ? they reintroduced it in AVPlayer HD ? I believed it was squeezed in every app of the store along with DTS. Then it may be a better choice than buzz indeed.

I have no preference between AAC and MP3, as long as you go higher than 192kbit/s both are fine, compression ratio is not exactly the same (AAC is preferred at lower bitrate) and purist say the sound is not the same that each codec has his own sound color. To be honest I never heard any difference between MP3 320kbit/s (lame encoder) and AAC 256kbit/s (itunes).

The DTS/AC3 issue was patent-related - so I am thinking the AVPlayer folks must have decided to pay the royalties on AC3. It is definitely convenient, since if it is your main MKV player on IOS you can omit a stereo encoding.

Assuming he wants the stereo anyway, I agree both MP3 and AAC sound fine at higher bitrates. My main thinking on AAC LC as the stereo codec is that it is widely supported and would allow remuxing to a normal MP4 format later on with no additional transcoding (and the associated quality loss).

Yes changed my mind as 312 is slightly more future proof and took your point on having Intel CPU as possible future server.