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[NickM]

Playing a ripped DVD is causing some strange sounds.  The problems seems to occur every 5 minutes of so; there is a loud click and the volume drops by 70-80%, then the volume slowly increases back to normal level.
This only happens when playing DVD's from the HDD.  The problems does not happen with playback using WinDVD.  An ideas what to look at??
nick

[Alex B]

That sounds like a typical automatic level control. What you described is similar to what stand-alone audio recorders do when an ALC circuit is used. What audio codecs/filters do you use?

[NickM]

Alex, I have the follwoing settings:-
Tools, Options, Playback, Output mode: Wave Out
Tools, Options, Playback, Output mode settings: Wave Mapper
Tools, Options, Playback, Video Playback Settings, Use Windows Media Player is checked
Tools, Options, Playback, DVD Playback Settings, Audio, Output Device, Default WaveOut Device
Tools, Options, Playback, DVD Playback Settings, Audio, DVD Filter List shows:-
Audio Renderer for MJ
Video Renderer
AC3Filter
Overlay Mixer
Line21 Decoder
Intervideo Video Decoder
DVD Navigator

Thanks, nick

[Alex B]

I think you have enabled automatic gain control in AC3Filter. WinDVD bypasses AC3Filter and uses its own system, but in your case MC routes audio through DirectShow and AC3Filter.

This is from the AC3Filter documentation:

Auto gain control - automatic gain control. It controls current gain to prevent overflow. Curent gain is shown at Gain level. When this option is disabled high-level signal is clipped on overflow what leads to unpleasant distortions. When this option is enabled then current gain will be decreased and overflow does not happen. System behavior after overflow is defined by One-pass normalize option. If One-pass normalize is disabled then current gain will be gradually restored up to Master level. In this case Master defines mean gain level. If it is many places when overflow occurs then this behavior can lead to unpleasant  'jumps' of audio level. In this case do not set Master level too high. This mode is recommended if overflow is not expected. If One-pass normalize option is enabled then gain level will not be restored after overflow. So each overflow decreases probability and 'strength' of next overflow and after some time gain will be stabilized to some mean value. Usually it happens after about ~10min of film playback. In this case Master level means initial gain for one pass normalization algorithm and may be set to maximum. This mode can provide maximum loudness with minimal artifacts. (see also Maximum loudness)

Try to change the "Auto gain control" options in the AC3Filter Mixer settings.

[NickM]

Changing the AC3 settings didn't make a difference.  So I have uninstalled it instead.  And still getting the same issues!

nick

[Alex B]

Strange, it must be some other filter then. One thing that is sure is that MC cannot adjust the playback volume because it does not decode the audio part of video files. MC uses system level codecs.

Use Windows Media Player is checked

Have you tried to disable this option? Does the same problem exist if you play the files directly with WMP? Do you have "Auto Volume Levelling" enabled in WMP? (though I don't know if it can work with video files)


One possible solution would be to try the FFDShow filter pack. Check this thread out for more information: http://yabb.jriver.com/interact/index.php?topic=33197.0