Well I will start off with I don’t think that there is such a thing as plain MPEG 2 files, there are a ton of options each product produces something different; If we wanted to there are enough differences we could easily use heuristics to identify which programs actually produced the original MPEG stream.
But back to my original point, on the high level DVDs can be thought of a play list (IFOs) and a series of mpegs (VOBs); but we can’t expect (although we might like) a regular MPEG player to play these VOBs seamlessly as they have a number of special things about them a typical MPEG would not, from my research this includes:
· Multiple audio streams (Directors commentary, alternate languages, etc.)
· Multiple video streams (subtitle overlays, alternate endings, alternate angles, alternate aspect ratios, etc.)
· Layer break indication (a marker indicating to move to the other side of the disk)
· Irregular time stamps (such as PTS and GOP headers, internal time stamps that are not sequential.)
The Windows VISTA and NVIDIA MPEG codecs handle these cases fine, however the Extender codec does not; one possible reason for this is that I bet the VISTA mpeg video path and the DVD video path have some shared code, in other words the mpeg probably gets played through the DVD decoder.
What sort of problems might you see when you run a VOB through a extender? Some that I have experienced include:
1. Session will hang when playing certain mpegs, the extender will need to be restarted – in my experience this happens most frequently near the end of the video or middle.
2. Video will “jump” around in nonsensical ways, for example in the middle of a video it might appear to play a alternate angle or jump around due to the Irregular timestamps.
3. Will only play a single audio track and you don’t get to choose which one
4. Will not play any audio even if one exists unless the default track (0x80 I think) is in present.
5. Video will end early, usually in the middle (I suspect this is the layer break frame).
If you want to play a VOB as a mpeg you have to remove the special things I described above, one way to do this is to use the “VideoReDo QuickStream Fix” feature, in my experience this fixes all of the problems (you set the Default AC3 hidden setting to 128 if you want to fix the audio problems too).