Okay, let me say up front that I am lost when it comes to this. I have MKV files, some with AC-3 (6 Channel), some either with a standalone stream or second stream of AAC. I am using MKVtoMP4 to convert these files as they are not playing correctly on TiVo (Premier). I try to keep the AC-3 (6 Channel) and no sound. I have to convert it to AAC (LC) 2 Channel and it works. I am transferring through the Tivo software. I am aware and have used pytivo and streambaby. I am just trying to understand this audio situation better. I have the Tivo connected to an Onkyo 616 via HDMI. The audio comes from the Tivo as PCM, which I also don't understand. My goal is to output is as 7.1 at the end of the day... Any insight would be greatly appreciated.