Author Topic: BUG v 1.01.11 - Problem with B Frame handling  (Read 2594 times)

November 20, 2009, 12:24:13 AM
Read 2594 times

timw

  • Newbie

  • Offline
  • *

  • 30
I encode videos using Elgato's Turbo.HD stick. It offers the following settings for the GOP structure:

I - Only I frames will be used.
IP - I and P frames will be used.
IBP - I, B and P frames will be used.
IBBP - I, B and P frames will be used.
IBRBP - I, B, P and R frames will be used.

Any setting above IP (i.e. those with B frames in) produces stuttery video on the WDTV Live (as if (e.g.) every other frame is dropped). I haven't verified personally, but apocryphally the higher settings work on the first generation WDTV which strongly suggests that the bug is with the WDTV Live rather than with Turbo.HD.

November 20, 2009, 12:29:48 AM
Reply #1

wiiBox

  • Guest
Nice find!

I assume this you can reproduce in software with something like the x264 codec?

Thanks for the heads up!

November 20, 2009, 05:59:02 AM
Reply #2

timw

  • Newbie

  • Offline
  • *

  • 30
Nice find!

I assume this you can reproduce in software with something like the x264 codec?

Thanks for the heads up!
Unfortunately it is a bit more subtle than whether there are B frames in the stream or not. It seems to be specifically the way that Turbo.HD uses B frames because I haven't been able to re-produce it with any of the software encoders (or at least, not just by adding/removing B frames). However, the critical step in getting a Turbo.HD encode working without judder on the WDTV Live, is to select the a GOP structure option without B frames. Hopefully that will be useful info for the engineers trying to fix the judder when so far the presence/absence has seemed to be pretty random.

If WD would like samples I'd be happy to supply them.

November 20, 2009, 11:00:29 AM
Reply #3

GuyWD

  • Jr. Member

  • Offline
  • **

  • 88
If you can post some samples I'll check them out.

November 20, 2009, 02:33:07 PM
Reply #4

timw

  • Newbie

  • Offline
  • *

  • 30
There is a limit of 128kb/post here. I've attempted to attach samples to this post, but they won't go through, is there some other mechanism I can use to get them through to you? It's just over 6MB.

Interestingly, I can't reproduce the judder now that I want to. With the last upgrade, some files juddered and some files had the video playing twice as fast as the audio. Prior to the upgrade they all juddered, but now I can only get the double speed playback - but the cross-over point between correct playback and double-speed playback is still the same: including B frames in the GOP structure. The -IP file plays correctly for me, the -IBP file doesn't.

Thanks for looking at this.

November 21, 2009, 01:16:53 AM
Reply #5

timw

  • Newbie

  • Offline
  • *

  • 30
After resetting my WDTV I only get the double speed video issue which suggests this is a duplicate of this bug. So the clues we now have, are that something that changed in the B frame handling of encodes made by hardware (I'm assuming Rev3 use hardware encoders and that this is the common cause so this is a bit of a leap) went from juddering to double speed video in this last release of firmware. I'd guess it would have something to do with frame ordering in the stream - but I'm no expert.

BTW, when I had the juddering it reminded me of some behaviour I'd seen before but couldn't quite recall. It turns out to be almost identical to the behaviour I get from my old divx box when it is given a "packed" stream. Probably not relevant, but the more info I can give WD, the more likely WD are to be able to isolate the problem.

November 21, 2009, 01:55:53 AM
Reply #6

jayallan

  • Administrator
  • Hero Member

  • Offline
  • *****

  • 1175
    • Jay Allan Photo
Tim,

You can email me the file or post it to a file share site and post the link here. 

I can't change the attachment size to more then 2 megs. 
WDTV LIVE with current official FW > HDMI > DVDO > Sony CRT Projector 150" 16/9 screen.  Toslink audio to Yamaha DTS receiver. No Network set up yet.

November 21, 2009, 05:56:06 AM
Reply #7

timw

  • Newbie

  • Offline
  • *

  • 30
If you can post some samples I'll check them out.
I've PMed you with a link to a couple of example files. Let me know if you need any more.

[Thanks for the offer, Jay. I've found an easy way of getting these to Guy via dropbox which will make supplying further samples easy, so I'll stick with that and not bother you]