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Fix for Windows 7 AC3 Dolby Digital Problem

Posted on Sunday, July 1, 2012 @ 02:25:37 PM CDT by David Yee [] [read 8784 times]

Tips: Windows-world
Recently I downloaded a video trailer of a concert performance in the format of an .avi file that supposedly has AC3 Dolby Digital sound in it. I hooked up a Windows 7 laptop (HP DV9000t), which has an optical SPDIF connection (via Mini Digital to Toslink), to a receiver that can decode Dolby Digital. I know this because I tested it and it works on Blu-ray movies w/ Dolby Digital (a red Dolby Digital icon appears when it is detected).

So I thought- oh maybe it's the sound card (Conexant chipset, according to the Device Manager) maybe not supporting Dolby Digital/AC3 pass through the SPDIF? To test this, I went to Control Panel, Sound, then double clicked on the "Digital Audio S/PDIF" device, then selected the "Supported Formats" tab. I highlighted "Dolby Digital" and clicked on the Test button.

The red Dolby Digital icon appeared on my receiver, and I heard the test chimes. Sweet- that confirmed that it does work, and the problem likes with the decoder/codec. I searched around and downloaded the K-Lite Codec Mega pack. Installed it, played the avi file again using Media Player Classic Home Cinema (MPC-HC), but still, no red Dolby Digital icon on my receiver. Darn it. I also downloaded the 64 bit version of the codec, and tried other players such as VLC, but still no AC3- doesn't matter if it were a 32 player or a 64 bit player.

I also used the default codec switcher tool by K-Lite, and changed all the decoding to be done by ffdshow, and ffdshow with DXVA (DirectX Video Acceleration), but still no work. I then decided to try to get more info on the file and decoding. In MPC-HC, I went to View, Renderer Settings, and picked Display Stats. It showed that okay, indeed ffdshow is doing the decoding. It also showed the "mixer" as "NV12". Apparently that had to do with the color, but the word mixer had me digging around for audio settings by the ffdshow decoder via the configuration tool "ffdshow audio decoder configuration". I looked through the options and went to "Output", then checked all the boxes under the Pass-through (S/PDIF, HDMI) section as all the boxes in there were originally unchecked. The checkboxes including Dolby Digital (AC3), DTS, Dolby Digital Plus (E-AC3), DTS-HD, and Dolby TrueHD. I then clicked Apply, and then OK, and played the video again and YES- now Dolby Digital is being passed through.

This ordeal took me over an hour to figure out and resolve. Hopefully this solution will help save some frustration and time with those of you having the same problem out there trying to get Dolby Digital to work with Windows 7 passing the sound to your receiver. I would imagine that this method may well work for problems other file formats such as mp4 and mkv files as well. I also believe that this fix will work on Windows XP and Windows Vista also.

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Fix For Windows 7 AC3 Dolby Digital Problem Rating: 2.5/5 (40 votes cast)

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