3_2 and 2_0 channels audio in azid

[lumi]

Hi everybody:

Could someone tell me, what will happen when I use

-L -3db -c normal

in azid for 2_0 instead of 3_2 channels AC3 audio ? I use these parameters for encoding of 3_2 channels sound, may I use it also for 2_0 channels sound ? If not, what parameters would be the best to use ?

Thank you.

lumi

[dhv]

For 2.0 ac3 audio don't use ANY parameters in Azid. Just plain "Azid.exe inputfile outputfile"
Eventually you may use auto find maximum gain, if you think the level is too low. The BIGGEST MISTAKE everybody makes with Azid is to use Dymanic Range Compression (-c normal). THAT RUINS THE SOUND COMPLETLY AND PERMANENTLY! If it is needed to hear compressed dynamics on small PC speakers, there are directshow filters that can do that in playback (like ReClock), but you still can hear full dynamics on Home Theater System if you want.

This parameter (-c normal) is suggested in Doom9 guides, and for that reason almost all encodings done with this manuals are with ruined dynamic range.

[lumi]

You say not to use -c normal when encoding 2.0 ac3 audio. And what about 3.2 ac3 audio ? Don't use it there also ? -L -3db is enough ?

lumi

[dhv]

Yes, for 3.2ch ac3 don't use it also. Unless you don't care about dynamic range, or you preffer to listen compressed dynamics.

That is what I use for 3.2 ac3: -L -3db -f on -g +6db
Instead of -g +6db you may use -maximize, but I prefer to keep relative levels of different movies soundtrack, so I always use constant gain.
For 2.0 ac3 like I said before, don't use any parameters.

[lumi]

What's the meaning of

-f on

switch and why to use it ?

By the way, you say that you use -g +6db instead of -maximize. I have met with movies that maximum able gain was under +6db, for example +3db. When you use your -g +6db, you can get volume overflow at some places in the movie and also ruin your sound completely.

lumi

[DJ Bobo]

-c normal has the same effect on 3/2 or 2/0 ac3 files. It will make a normal dynamic range compression.

-L -3db will lower the volume of the bass channel by 3db. I have been told, this is to protect the speakers from any "overreacting", but I have to see any damage yet on my system, so it's not rea~lly necessary in fact. If you see a .1 (like in 5.1), your ac3 file has a bass channel. Obviously, 2.0 hasn't any bass channel, so it's useless/senseless to include it in your command.

And yes, -g6db will cause overflows on many movies/series. If you're dealing with a movie, just use -a (which is what dhv mentionned as maximize, but well, it's faster to type -a :D).
If you're dealing with a series, put -N on every command for each episode to find out the max gain you can apply, then make a normal command with that gain.

For the meaning of -f, check the readme of azid. Never used it btw

[dhv]

parameter "-f on" means rear channel filtering, and it is nessesary for proper dolby surround downmix. If you mix to plain stereo, -f must not be used.
As I say before, I use gain +6 db only on 5.1 soundtracks, because the downmix level from 5.1 to 2 channels is very low. This value (6 db) I have found myself experimenting with encoding and decodind test ac3 files with various levels of the 6 channels. With that gain, 90% of soundtracks don't produce overflows, only the loudest movies sometimes produced overflows at few samples, but this is completely unaudible. 50 or 100 or even few tousands of samples are 0.001% of whole movie, and overflows are no more than 1 db
And I always may decrease the gain if I find it nessesary. By the way, if some soundtrack produces too much overflows at +6 db gain, then the level of the individual channels is so high, that the sound is alredy distorted before decoding. I personally have found movies with such soundtracks. (Face/Off for instance)