According to avidemux, the audio is ac3 6 channels.īut that didn't work initially. I tried on my roku 3 and roku 2 same thing. I tried another mkv, this one didn't stutter, but was just silent. I just used avidemux (never liked that in the past but seems to have matured a bit, but I'm going to try other tools suggested here thanks!). Also, I've found that if they'll play on the Roku they'll play on pretty much any device. The Roku Media Channel works just fine for the local and DLNA served files I've quickly remuxed and only occasionally have I had to fiddle with the video stream ( !details/2213/roku-media-player). Plex is a common answer in this sub for these types of questions and is an awesome option, but it can be overkill depending on your needs (and requires a "server" to be running). Occasionally, if your audio bitrate is very high you'll get the stuttering you are seeing (it will also happen if your network connection isn't quite up to the task). Roku can typically handle AC3 surround easily as well but can be more finnicky about it in MKV files. The easiest and most compatible audio codec is AAC Stereo (pretty standard in MP4 movies and digital streams). Generally it's just the audio that needs to be changed and that takes much less time than a full conversion.
It's faster than converting and keeps the quality. I use XMedia Recode to remux my files to be more Roku friendly. Roku 3 definitely handles files better than Roku 2. This guide does a good job of explaining what codecs are typically supported.
So the Roku has to choose a particular audio stream to pass along, it can't send both." It doesn't send the original file over HDMI, the Roku has to take the original and then send the video and audio in the way that the HDMI spec dictates. I'm not an expert on HDMI, but think of it as sending audio and video in its own format. You have to put your Roku into the 5.1 mode for it to send that track over HDMI. If it's connected to a receiver, it can also pass through AC3. Basically, the only thing that the Roku understands and can deal with on its own is stereo AAC. "Stereo AC3 is only supported if it's passed through to a receiver that can process it (receivers will typically display PLII for this). I wish they could fix this in a firmware update or something.
So even if it's two channel AC3 it can't play it natively. Meaning you have to have a receiver that can handle it. Roku basically only supports it on passthrough.