AC3 equalization

maoumaou · Jul 3, 2006, 05:31 AM

Hi all,

I'm a speaker DIYer and i've been using kx with audigy 2 for quite some time. It helped me twice, firstly by using it as a digital crossover to drive my 3-way speakers directly with a separate amplifier for each driver and secondly, after building my 5.1 system, to equalize the different speakers used in order to get a homogenous result in the frequency responce (using measuring mics etc...).

Th ie problem is that whenever I want to listen to an ac3 stream I have to decode it first using a software decoder, pass it through my "equalizer" and then through "analog out" to my 5.1 amplifier. I would prefer to use my amp's hardware decoder instead but still be able to equalize the ac3 stream before reaching my amplifier through the SPDIF. That is decode the ac3 -> equalize it -> encode it -> pass it to the amp using the SPDIF. Any ideas???

Another thing although not really 3-d audio oriented, is it possible to use two audigy2 cards with kx in parallel? For example, use one as the main card (ac3 decoder), connect the digital out (Fl, Fr) to the digital in of the second card, and use the second card as a digital crossover with some delay functions to correct the timing issues???

Thanks

Tril · Jul 3, 2006, 07:15 AM

Take a look here : redocneXk released - Realtime 5.1 ac3 Encoder
and here : redocneXk (GUI version) released - Realtime 5.1 ac3 Encoder

I am the author of these. Please give some feedback if you do try them. I can only fix bugs if they are reported to me.

Keep in mind that when using an AC3 encoder, you add an encoding delay. The delay is mainly due to having to wait to fill the audio buffer of 1536 samples.

The GUI version is more recent and it's easier to use but both versions should work equally well once set-up correctly.

maoumaou · Jul 3, 2006, 11:31 AM

Great job!!!

At last I can play with my system and fine tune it.

How do the values in the matrix relate to volume. Is it only a multiplier, or is it in dB?

The program crashed some times, I'm not sure yet when that happens cause I've been playing around. I also get pauses some times when a stop and restart the encoding. I think someone else posted that before.
The 640000 bitrate seems unstable. I used randomly 384000 and it works. Again don't consider this as a feedback cause I need to work with it a bit more.

What is the difference between Surrounder and Surrounder+? I use the first one until I set up the DSP correctly.

Thanks for the help, I'll keep you posted if I find anything new...

Maddogg6 · Jul 3, 2006, 11:53 AM

Quote:

What is the difference between Surrounder and Surrounder+? I use the first one until I set up the DSP correctly.

The surrounder+ is used by cards that can do 7.1 - as it needs the additional routings/decoding to support that mode. (not sure which models tho - but the A2ZS does for sure)

And Im sure there are 2 different ones, because of resource used needs to be less for 10K1 based cards.

Not sure if there are other differences - but thats the most obvious one to me.

Tril · Jul 3, 2006, 05:54 PM

Quote:

Originally Posted by maoumaou

How do the values in the matrix relate to volume. Is it only a multiplier, or is it in dB?

Only a multiplier.

I posted the new version of redocneXk with a GUI a few weeks ago and I never received any feedback. The new version must have gone unnoticed.

Try to play a little with the ASIO latency settings. It may help.

maoumaou · Jul 4, 2006, 02:24 AM

Thanks for the replies

Tril, in terms of quality, how do you think the consecutive encodings-decodings affect the signal, even if it is in the digital domain?

Also, since you obviously know how ac3 works, how do you compare some decoders like the one used in Powerdvd or the AC3filter? Any beter suggestions?

Tril · Jul 5, 2006, 04:11 PM

AC3 is lossy but when encoded at a high bitrate, the quality is good. Listen to your ears. If you can't hear the difference, then don't worry about it.

maoumaou · Jul 11, 2006, 11:02 AM

Hi again.

Finally, I finished setting up the DSP. RedocneXk is mostly stable with the default settings and always on real time priority. To get it working properly I have to restart it a few times. I tried playing with other latencies in ASIO other than 21.33. Above that I cannot even select them. It reports that it is too big for the current channel setup. Below that my amp seems to loose synchronization with audigy2 and the sounds keeps on muting instantly. Any ideas why?

I also posted a screenshot of my dsp. The idea as I said before is to use EQ peaking and equalizers to balance the frequency response of the 5.1 system so that all speakers sound the same. I'll try to use proFX plugins in the future to make it simpler.