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Odd AAC sound playing back HD recordings in VLC

Discussion in 'HDR-FOX T2 Freeview Recorder' started by Philbert, Jul 14, 2012.

  1. Philbert

    Philbert New Member

    Hi, I'm hoping someone with an HDR FOX T2 has come across this before as its proving a bit tricky to search for!

    HD recordings transferred to a PC playback perfectly in all recent VLC releases...except for the AAC (MP4a) audio. Best way to describe it is whenever the audio peaks, some kind of 'clipping' occurs and the volume level drops down to something fainter and quickly recovers back to normal, until the next peak triggers it again. In sonically busy scenes, this turns into a complete mess.

    Funny thing is, the sound plays back perfectly in media player classic home cinema (with the latest klite codec pack), but picture stability has a hard time due to skipping/fast forwarding small sections in what looks like an attempt to keep in sync with the sound.

    Both players use their own install of FFDShow, but each uses a different plugin to handle the sound. Its not the sound card or drivers but the way vlc handles the audio format.

    I have only found the exact same problem on Doom9s forums, with someone trying to play back an HD recording made with a Panasonic Freeview HD box on vlc. His solution was to use mpc-hc, as I guess he had no picture problems with it.

    Any advice please?
     
  2. grahamlthompson

    grahamlthompson Well-Known Member

  3. fenlander

    fenlander Active Member

    A few questions to help the diagnosis:

    Can you name a few examples of recent recordings that do this so that we can see if the problem is reproducible on another system? Does it happen equally on all HD channels?

    It seems to me that if the file plays correctly in other media players, the most likely source of the problem lies with VLC, but the fact that MPC-HC (which is one of the least demanding players in terms of resources) also struggles might indicate that your PC is under-specc'd for the purpose. So - what's the PC/OS spec?

    Finally, how did the files get from your Hummy to your PC? How did you unencrypt them? Were they edited on the Hummy or elsewhere before use? Are you playing them direct from the Hummy via a network share, from a NAS or from a local disk?

    Oh, yeah. As Graham said, do try Splash - the Hummy's little helper. In resource terms, VLC is a monster compared to Splash and trying to find a solution to any sort of problem in the maze of its configuration screens is not for the faint-hearted.

    EDIT: Afterthought. I have noticed some audio effects very similar to those you describe in some downloaded HDTV episodes. I haven't found a complete explanation, but my guess is that they're connected to unbalanced 5-channel sound, where the back channel volume ramps up automatically whenever there is minimal output on the front channels. I don't have a home cinema system, but I can mitigate this in Splash by muting all sound channels except the centre front.
     
  4. Philbert

    Philbert New Member

    Only done one HD recording so far (Raiders of the Lost Ark from BBC1HD last week, absolute classic) and got it onto the PC using the 'double copy to/from USB with opt+ after clearing the enc flag' trick, so no problems there. No probs with the PC spec either, I7-2600, GTX460, SSD HD, X-Fi Titanium and XP home (ahem). The recording is totally unedited, it is as the HDR recorded it with nothing added or changed. Is it possible that HD recordings from other HD channels may not have this audio problem, I think I saw something about different channels playing back differently?

    Just downloaded splash lite 1.7.1, I'll give that a go at some point, cheers!
    Noticed refs to it while trawling for clues, I see it even claims to work on netbooks, hmm...
     
  5. fenlander

    fenlander Active Member

    My wife's little Samsung netbook plays 720p happily with Pot Player or MPC-HC, but it needs a CoreAVC codec to do it. It can't handle HD files in Splash, but any recent netbook with ION graphics should manage perfectly.
     
  6. grahamlthompson

    grahamlthompson Well-Known Member

    Vlc is very choppy with HD on my i3 17" laptop. Splash plays back perfectly.
     
  7. fenlander

    fenlander Active Member

    I think one dodgy recording doth not a major problem make.... Best to try a few more from different channels and see if the issue can be replicated.
     
  8. Philbert

    Philbert New Member

    I don't think its a dodgy recording as apart from the picture problems in mpc-hc and audio problem in VLC, its fine on everything else stand-alone I play it back on.
    The audio problem only occurs on PC when VLC is playing it back, it does it on both my I7 PC with 5.1 setup and my scoddy work PC with onboard sound/internal speaker (quite easy to spot), so it certainly is VLC somehow.
     
  9. Black Hole

    Black Hole Felonius Gru

    As an aside, how did you get that? I thought it got bumped off because of the Wimbledon coverage.
     
  10. fenlander

    fenlander Active Member

    I occasionally find files that won't play in one player but are quite happy in others. I currently have some .mov files that have no sound in Splash but are perfect in VLC and an mkv copy of Hannah that crashes everything except Pot Player. It's why I keep 4 players on my PCs. So far as Hummy HD files are concerned, they have mysteries of their own. For example, recode them in Freemake or Handbrake and try to work out why some encode perfectly and others either crash or just terminate early. Even VideoReDo - the gold standard for editing TV files - fails to save Hummy transcodes except as ts files (no mkv, mp4 etc.). Nowadays, I just watch 'em on whatever will play 'em - I turned in my anorak a while back.

    Just as a matter of interest, have you tried watching the film in VLC via uPnP? If you haven't tried it, run VLC, then View-Playlist. Select Local Network-Universal Plug'n'Play. It should list your Hummy. Navigate to the original (non-decrypted) version of the file and select. Finally, it's also possible to watch a file on the Hummy in your browser, provided you have the custom firmware installed on the Hummy and the VLC plugin installed in your browser. I find the browser option to be much smoother than normal use of VLC, but you don't get any ability to FF/RWD.
     
  11. fenlander

    fenlander Active Member

    Rescheduled to July 7th 18.30 BBC1 HD.
     
  12. Black Hole

    Black Hole Felonius Gru

    Eh? I think that's when I expected it to be.
     
  13. fenlander

    fenlander Active Member

    I think it was originally scheduled the previous week. Could be wrong.
     
  14. Brian

    Brian Administrator Staff Member

    Yes, Raiders of the Lost Ark was scheduled for 30th June but was postponed until 7th July, where it replaced Indiana Jones and the Temple of Doom, which was itself postponed until 14th July.:)
     
  15. Black Hole

    Black Hole Felonius Gru

    Eek! A whole week of my life just vanished without trace!!
     
  16. Philbert

    Philbert New Member

    No joy with Splash Lite unfortunately.
    Immediately noticed the inferior picture quality, ie. 'jaggies' around strongly defined edges where there weren't any previously, which leads to an overall softer picture - could this be where it gets its performance advantage from, by some kind of downscaling? Its the Lite version, so the options that could reverse this are either not there or greyed out, such as hardware acceleration. The picture starts to suffer from some bad breakup after less than 5mins playback anyway, so the lack of options doesn't really matter any more.

    VLC still has the best picture handling, just a shame about that blasted sound.
     
  17. fenlander

    fenlander Active Member

    For some time now Splash (the Pro version) has been my standard viewer for ts/mkv/mp4 files. I'm running it on a modest media pc and I never see the degradation you describe. It's not quite as low-resource as Pot Player or MPC-HC and not as flexible as VLC, but for the files I use most often it's near flawless. I suspect more and more that you have a rogue file. The fact that some players can handle it does not mean that it has no faults that could render it unplayable on others.
     
  18. Philbert

    Philbert New Member

    Tried a couple of non-humax HD files with it and saw similar softening. Perfect downscaling a normal reaction to slightly iffy files??
    I think the free lite version is going to be inferior to the paid-for pro version in all the right places otherwise the pro won't sell, so I'll put it down to that.
    Back to square one !
     
  19. grahamlthompson

    grahamlthompson Well-Known Member

    I have Splash Pro EX and Splash Lite can't say I have noticed any difference. I only view at 900 x 1600 though. Pro EX adds features like video conversion and frame capture. Simple editing is also supposed to arrive sometime.

    http://mirillis.com/en/products/splashexport.html

    http://mirillis.com/en/products/splashexport_comparison.html

    Pro Ex only costs about £16.00 and you can try it for free.
     
  20. fenlander

    fenlander Active Member

    The detail enhancement feature (sharpening by another name) in the paid-for versions does make an appreciable difference on large screens. However, the version used should not affect the jaggies and picture break-up you describe: I have never experienced anything like that. All the premium versions can be tried free.