dociso wrote:
VLC media player has no problem providing high quality search and slow motion both forward and back in most video files – why not WDTV hub?
Well, actually VLC does have problems.
VLC was designed to (and advertises that it will) play bad/broken files. Thus, it tends to ignore specs and do things its own way.
Technically, for any video stream, playback is only supposed to start at a sequence header, so that all the proper values for that sequence can be read and applied.
You don’t notice this with things like DVDs, because the sequences are 15 frames long… if you tell it to play back at a certain point, you can’t tell which frame it’s actually starting on… playback starts at the start of a sequence.
But, other encodings can use longer sequences. In fact, the entire file can be one sequence.
The WDTV devices only support playback at the nearest sequence to where playback has been requested – even if you specify an exact frame timecode in a chapter mark, playback of that chapter will generally NOT begin on that frame… it will be at the nearest new sequence to that frame, so that all the correct settings for that sequence can be read.
VLC ignores this requirement – you can start playback anywhere… but unless you do start at a new sequence, the video output WILL generally be garbled until a new sequence header and I-frame is found. If the sequence is long, the screen can remain garbled for a long time. Again, if the sequences are short, you often don’t even notice – it totally depends on the encoding.
It doesn’t seem to be in WD’s interests (regardless of whether the chip has the processing power or not) for playback to be “mangled” every time you FF or REV. It seems to me as if WD is better off sticking to the specs and playing back from the headers, as is spec’d out. That way, the video is always going to look right when it plays. But the downside is that playback may not be where you want it to be. Some bad encodes have very long sequences, and if you FF or REV, sometimes the actual playback point is 10 minutes off (or more). But the way to avoid that is to just not make bad encodes – not to break proper playback. Because those same bad encodes don’t play “properly” in VLC either – the only difference is that playback starts where you ask instead of where it “should”, but/so the screen is garbled.
And again, the screen updates when FFing and REWing are problematic. The WDTVs just don’t have the same processing power as a PC… they can’t really generate frames on the fly, and pretty much have to rely on I-frames. If you try to FF a file that has short sequences on a WDTV, then you do get frequent screen updates, just like with any other DVD player. But, if you try to FF/REV a file with long sequences, then there aren’t nearly as many I-frames to work with and the screen updates are much fewer and farther apart. The WDTV simply doesn’t have any frames to display in the interim, and it can’t really generate intermediate frames like VLC can. So again, the lack of “smoothness” is totally dependant on your encoding. If you create (or download) files with very long sequences, then there just won’t be many frames for the WDTV to display while you’re trying to scan through and it will display what it physically can.
But you can’t really blame the WDTV for properly handling poor encodes. It’s much better to just make decent encodes to start with, and then the files will play (and FF/REV) as you expect them to. Or, if you insist on using bad encodes, then it’s better to use something like VLC that advertises support for bad/broken encodes, instead of a hardware player that expects the standards to be met.
