avi_ac3 spdif pass through to receiver, no front sound!

[9mood]

Hi guys,

I searched and read every thread with "spdif", but none of them solved my problem.

I want to play AVI with 5 channel AC3 track on pc and output the video part to tv and sound part to receiver. The video part goes through smoothly. For the sound part, the receiver recognized the input signal as dolby digital, but I can hear only the surround speakers (no sound from front 3 speakers) in surround mode (of the receiver) unless I switched to stereo mode. I tried with both the onboard sound and a creative sound blaster digital value, with either optical or coaxial calbe, same results. I also tried using the digital mini jacket at the sb live card through a mono rca adapter, same result, I can't get the real dolby digital 4.1 surround sound.

Following is my hardware and software configuarations:
VIA P4PB 400 mb with onboard VIA VT1616 6 channel AC'97 codec and SPDIF bracket (which has optical and coaxial jacket)

Creative Sound Blaster Digital Value with Digital I/O Card.

Sound cards have been set to digital output only

Monster Optical and coaxial cable

MS Windows 2000 Pro Sp4

WinDVD 5 Platinum, choose spdif in audio setup
I also tried the ac3filter 0.70b with Classic Media Player, same result as with windvd's audio filter.

Receiver: Onkyo TX-SR500
Speaker: Onkyo SKSHT500 5.1
Receiver and speaker have been tested with dolby digital DVD setup disc. All speakers are passed the test.

I verified the avi file with virtualdub which indicates that it has 5 channel ac3 sound track.

Where could be the cause of the problem? The software player? The sound card or the receiver? I need some advice. Thanks in advance for any input!

[brute]

strange. If you put the signal through SP-Dif the signla isn't changed, so there cannot be such a problem. The only thing i can imagine, is, that the AC3 file isn't the original one, I mean, that someone ripped it, then reencoded, or downmixed it, and then muxed it again.
In the reencoding prcess could happen a wrong setting or something like that.
In fact that must be the problem, there is no choice, the ac3stream should be broken.

[9mood]

The ac3 stream does not seem to be the fault for I tested with not only one avi_ac3 file. I tested with DVDRip_AC3 files made by groups as well as one made by myself which I can gurantee no reencoding or downmixing, directly stripped from DVD, same results. The symptom is that I can not here dialogue while all surround sounds are there in surround mode, unless I switch to stereo mode.

[9mood]

At last, wired thing shows up! When I played the same avi_ac3 files at another computer (OS: win2k pro sp4; sound card: sb live value) and checked the intervideo audio filter, in the Current audio track window it shows
Format: AC3
Attributes: 16bit/5.1ch.

Then I check the same thing at the computer mentioned at the top, it shows 16bit/2ch! Now I'm wondering how can this happen! Is it possible that Windvd treats the ac3 stream differently, or the driver for the sound card matters? Help!

[brute]

what happens when you use PowerDVD or Windows Mediaplayer with AC3Filter, do they show the same weird things?

[9mood]

I think I found something.

Remember I tested my receiver and speaker's set-up with a dolby ditigal test DVD? OK, I copied the vob file for that test to hard drive and played it with classic media player. Every speaker uttered sound when it should! Then I ripped the ac3 stream with dvd2avi and played this ac3 file with classic media player, all speakers passed this test as well. Therefore, I can say that the sound card, the OS, the playerbacj software, the driver, the audio filter, the receiver and the speakers all works fine except the ac3 sound stream in the avi_ac3 file.

But according to my knowledge, the ac3 stream file should be ripped directed from DVD when people made a dvdrip_avi, then how came something could be messed during this process?

[9mood]

Mystery solved! My the cable of the central speaker is loose:( ac3filter helped me to locate this problem. When I played the avi_ac3 file again, I looked into the properties of ac3filter (set output to 3+2), I can see the input and output status. There I found that dialogue is mainly at the central channel. Then I did the speaker test with my test DVD, I had to admit that I overlooked the central speaker during all test.

Thanks everybody. Case closed.