Lossing quality when converting from wav to ac3 5.1 ?

[dyanglp]

I used SoftEncode to convert some wav music to ac3 5.1 and playback with PowerDVD, the quality obviously goes down. I tried Vegas 5.0 and gained the same result.

Encode setting:
Data rate: 448 kbps; Sample rate: 44.1 kHz; LFE enabled;
Audio coding mode: 3/2;
Bit stream mode: Main audio service complete main
Dialog nomalization: -27dB; Audio bandwidth: 20.71kHz
Mix level : 105 dB SPL; Room type Not indecated
Preprocessing: DC high-pass filter, Bandwidth low-pass filter, LFE low-pass filter; RF overmodulation protection: checked

Most parameters are default. Am I doing something wrong ?

[timmyp]

Well, AC3 IS a lossy codec...

http://en.wikipedia.org/wiki/AC3

So you theoretically WILL have a loss of quality due to the compression techniques used. The question is whether it's noticable or not.

What, exactly, are you hearing that causes you to make the statement "the quality obviously goes down".?

[dyanglp]

Timmyp Wrote:

What, exactly, are you hearing that causes you to make the statement "the quality obviously goes down".?

It seems to me that some high frequency part was lost (how high ? I don't know). Is it due to those filters ? I wish I could attach the wav and ac3 here.

[timmyp]

I don't have a lot of experience using audio filters, but I'm sure someone else will chime in here and offer some advice.....

In the meantime, you might try selecting a small sample from the project and converting to AC3 using no filters, then 1 filter, then a different filter and so on, to see if you can identify what is causing the loss of the highs.

Good luck!

[midnightsun]

It might be that some high frequency got cut since by what you posted your dialog normalization is set at -27dB, while its standard value would be -31dB.

There's a big FAQ thread at the top of the audio forum at doom9 where this stuff is explained in detail. Might be worth cheking out.

[erratic]

The default AC3 settings in Vegas lower the volume a lot.
To avoid that, use these settings:

Dialog normalization: -31 dB.
Dynamic range compression: None.

I've only used AC3 2.0 but I assume this also applies to 5.1 surround.

[virendra]

All your settings are ok except sample rate of 44.1

Since you are using power dvd means you are using computer to play the file and not the stand alone dvd player.

Re-encode your file to 48 instead of 44.1 and then convert to ac3 by softencode and now it should play well