Video starts out fine - slows down in a few minutes


#1

Have been looking for some info on this issue, but no luck so far.

Playing MKV file over a Linksys PLTK 300 Powerline AV kit - so not exactly wired and certainly not wireless.

All Internet options are working perfectly, audio plays without problems.

MKV and BD files start our fine, regardless of resolution they are recorded with, then several minutes later start to stutter. Everything becomes slow motion and audio disappears.

Have to say that all these files play perfectly with USB connection, so naturally the first to mind is connection speed.

Just can’t understand how playing fine for several minutes would figure into speed problem.

Would appreciate if anyone has any thoughts.


#2

Most likely the videos are encoded VBR, and if you examine them you’ll see the bitrates starting to peak right when the dropouts occur.


#3

Although I am not that familiar with VBR, I tried many MKVs from different sources - highly unlikely every single one of them has the same exact encoding. It seems that you know quite a bit about this from your other postings. If you don’t mind me asking, why would bitrate increase in a stream? Or is it actually decreasing? I am assuming WD Live has a buffer built in - so my guess is - it receives a chunk of stream at the start and then struggles to keep up with it.

Does that sound plausible?


#4

VBR is variable bitrate encoding, and many (most?) videos do this – it preserves the absolute best quality (because you are only encoding high rates when the data justfies it).  But as I suggest, you can tell by looking at the rates using a freeware viewer like VLC.

I can’t imagine the Live having a buffer –  it sure doesn’t act like it based on my experiences (I have a high bitrate video I use to test things and using it over my wireless network brought it to its knees, which is why I switched to wired).  The Live is only playing what is given to it, so having a buffer in IT wouldn’t really make much sense (it would be like having a delay in your television set – just doesn’t make any sense not to display information as it is received).  If the Live buffered data you would see a delay when you pressed Play on something (and this is something you definitely do NOT want).   A buffer would make far more sense in whatever is delivering the content, be it hard drive or router.


#5

I see. So the only answer to any of these issues is a wired connection.

I am looking for a tool that might help me measure the speed of Lynksis Power Line AV kit.

Clearly it’s not providing speeds up to 200 MBits/sec as advertised, but I am interested to see how does it compare with a regular Cat5 running 100 Mbits/sec.


#6

Just like IQ tests (which only measure what IQ tests measure) measuring the speed of your network isn’t exactly going to do you any good.  I tried out an N router, for example, and the rated speed of that was much higher than I would ever need and yet still it didn’t stream well enough to play my highest bit rate movies.  The only practical thing is what works and what doesn’t.

IOW, suppose it tells you your wireless is running at X speed.  So what?  If it doesn’t work for you then it doesn’t matter what the speed says (which is why I have files I can test out to see if the speed is adequate or not).  There are SO many things that can impact even a fast network (which is why sometimes your cell phone works great and then, in the same location, you can’t even get a signal) that it’s a bit like chasing your tail trying to figure it out.

With HD media wired is almost always going to be the answer (and wires are not evil, trust me – while I wasn’t happy about it, I wired up my entire house in just a morning and I’m a very old man :>)


#7

mkelley wrote:

VBR is variable bitrate encoding, and many (most?) videos do this – it preserves the absolute best quality (because you are only encoding high rates when the data justfies it).  But as I suggest, you can tell by looking at the rates using a freeware viewer like VLC.

 

I can’t imagine the Live having a buffer –  it sure doesn’t act like it based on my experiences (I have a high bitrate video I use to test things and using it over my wireless network brought it to its knees, which is why I switched to wired).  The Live is only playing what is given to it, so having a buffer in IT wouldn’t really make much sense (it would be like having a delay in your television set – just doesn’t make any sense not to display information as it is received).  If the Live buffered data you would see a delay when you pressed Play on something (and this is something you definitely do NOT want).   A buffer would make far more sense in whatever is delivering the content, be it hard drive or router.

I think you will find that the WDTV does have a buffer. I am running with a wireless dongle on a g network and when I start up a movie it flashes like mad for some time before starting. Also if you  switch off the unit when playing an audio file, the audio keeps going for some time.


#8

Ah, I sit corrected (because I’m sitting).

(However, it doesn’t do that for me when I press play – it immediately starts playing.  I wonder if it’s the difference between wired and wireless.  It also immediately stops if I disconnect the CAT5 cable).


#9

mkelley wrote:

Ah, I sit corrected (because I’m sitting).

 

(However, it doesn’t do that for me when I press play – it immediately starts playing.  I wonder if it’s the difference between wired and wireless.  It also immediately stops if I disconnect the CAT5 cable).

As you say maybe it only buffers the wireless stream.