You may find that a particular source file has audio problems that may be fixable with AC3Filter's Mixer. Rather than attempting to guess what settings to use you can use the AC3Filter tray icon to enter a realtime configuration dialog where you can adjust settings during playback. In this mode, the Properties dialog also displays realtime output levels so you can monitor them as you adjust various settings.
Tray Icon
In order to perform realtime adjustment you must have Show tray icon enabled on the System Tab. This must be done in Offline Configuration mode (from the Start Menu shortcut). When AC3Filter is in use a tray icon will appear which you can click on to display the Properties dialog. Changes made at this time will be reflected in playback immediately.
Volume and Gain
Generally the only thing you should need to adjust during playback is volume, but simple as it sounds it can actually be quite a complex subject. For example, if the volume is too low from a particular video file your first instinct may be to increase AC3Filter's Master Gain, thereby increasing the volume of each channel. However, when you increase gain you run the risk of the loudest sounds being distorted.
Viewing Levels
Rather than relying on your ears to tell you when you've created distortion problems, you can use the Levels meters in various parts of the AC3Filter Properties dialog to show you them to you. When playback is occuring and the Mixer is active (passthrough to S/PDIF not enabled) you'll see a display of each channel's current level. When a particular channel's level meter turns red its gain needs to be lowered. As with offline configuration that can be done on the Main tab for all channels or on the Mixer tab for groups of channels or even each one individually.
Lowering Peak Volume with DRC
One way to compensate for high peak levels is to enable DRC, or dynamic range compression. This clamps (scales) the volume so that the highest and lowest volume sounds are closer to each other, reducing the peak volume accordingly. Keep in mind that most surround sound encoded audio already has some DRC applied, applying it again with AC3Filter will reduce the volume difference from the softest to loudest sounds even further. It's generally better to use a lower gain instead to avoid this.
Adjusting Audio Sync
If you experience problems with the audio being either slightly ahead or behind the video you may be able to fix it using AC3Filter's Time Shift slider. If the audio is ahead of the video slide the bar to the right. If it trails the video slide to the left. In some cases there are other problems, such as errors in broadcast TS (MPEG-2 transport stream) captures. In these cases you may need to run the file through some sort of repair tool1 before playing. In some cases it may also help to demux the video to elementary streams and re-mux them again2.
Changing Offline Settings in Realtime
One quirk of AC3Filter's realtime configuration is that settings are saved once you enter them, whether you click the OK, Apply, or Cancel button to close the dialog. These settings are also saved as part of AC3Filter's Offline Configuration, so if you're using settings you don't want applied permanently make sure to set them back to the correct values.
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Just a few years ago the only multimedia containers most Windows users had to worry about were AVI and MPEG-2 Program Streams. Although a number of other proprietary, and even open source containers have been used, for MPEG-2 or MPEG-4 (ASP) video AVI and MPEG-2 PS (.MPEG / .MPG) files have traditionally been the standard. With the development of MPEG-4 AVC (H.264) video the MP4 and MKV containers.... (Read More)
ffdshow Installation and Configuration
As new video and audio formats continue to be developed it's becoming harder and harder to make sure that your computer has the required software to playback the latest multimedia files. If you suddenly have a need to playback a format you've never seen before the last thing you want to do is spend hours figuring out why it won't play, only to discover you need to buy a new decoder of some kind. If you don't want to keep installing "just one more" codec, or worse yet an assortment of codec packs.... (Read More)
Version History v1.0 2008.03.21 Original version by Rich "vurbal" Fiscus
