I've got a collection of DVDs and blu-rays I've ripped to my computer with each being in an mkv file with the streams within simply verbatim what was within the DVD or blu-ray. When playing the files on my PS3 via PMS they all are encoded into mpeg2.
One workaround I've found is to convert the DVD-based mkv files to m2ts using tsmuxer and then telling PS3 Media Server to not transcode files with that extension. Plays just fine. However, I can't do that with many of my blu-rays because tsmuxer doesn't support some of the audio formats from the blu-rays, and I'd prefer to maintain the original quality if at all possible. The PS3 can natively play these formats; it's just the container that's different. Is there any way to tell it through settings to simply pass the streams through for files which contain streams the PS3 can play natively?
