Converting AC3 surround 2ch to dplii WAV

[Moti172]

Hello

I want to convert AC3 surround 2ch to dplii WAV and than to MP3, using Azid and Lame.

What is the correct syntax using Azid?

I'm using
azid -c normal -s dplii --maximize -L -3db 1.ac3 1.wav, when converting 6ch AC3 to dplii wav, but does the 2ch AC3 contain LFE channel? if it does is allready dplii and when I add the -L -3db the LFE channel is reduce in another -3db?

Thanks

[Skelsgard]

If the AC3 is 2-ch Surround matrix-encoded (wich most movie AC3 2-ch are, in DPL) then u don´t need to specify any conversion parameters. 2-ch sources are already 2-ch. I konw this sounds stupid but pay attention.
DPL/DPL II are dowmixing matrices used to get 6 channels to be transported within 2 channels, by applying specific mixing algorithms. They are not lossless compared to the source since (based on the way the algorithms work) infomation from one channel can leak to the others in the upmixing/decoding process.
2-ch AC3s are usually already DPL encoded, that means that the matrix as already been applied. So u´ll have to upmix with an DPL matrix to 6-channels and then downmix again with a DPL II matrix back to 2-ch. In the upmixing and downmixing you will be losing info and therefore quality. Now consider that it comes from a compressed source (AC3) wich has already lost quality in the process (as being downmixed to 2-ch). And u would need to apply algorithms that would progresively decrease that quality even more.
The only source to do proper DPL II downmixing is an 6-ch AC3 (considering that is very unlikely that u can get the original uncompressed track masters from the dude that mixed the audio).
With all this consider, you can now understand what mean with "2-ch sources are already 2-ch". AC3 2-ch are already DPL encoded, so the only thing u would need to do is to transcode form the AC3 to WAV and then encode to MP3. No need for AZID, since there is no real channel downmixing being the source (the AC3) already 2-ch.

- There is no LFE channel to downmix when the source is 2-ch.

Sorry for the extent of the reply.

[Moti172]

Thanks alot for the response :)

So ,if I get you right, all I'll need to do is convert the 2ch ac3 to wav. I'm using azid version 1.9 ,so the correct syntax will be:
azid -c normal --maximize 1.ac3 1.wav
There's a deafult switch in azid v1.9: -L -3db, and if there's no LFE channel , will it have any negetive affect on the result?

Thanks again

[Skelsgard]

-c normal --maximize
Use the -c if u want to apply Dynamic Range Compression. But understand this: DRC will maintain the overall sound level so that the sound doesn´t boost itself up enough to damage your ears or your equipment when played. That means that if i.e. an explosion happens, the sound will drop to maintain a specific gain, while during low talking the sound will be boosted to maintain that same gain. This is a personal preference. You can either use it or ignore it at will. The maximize option is a normalization, I know you know that, but you should consider how it affects the overall track level, if u are also using DRC.
There's a deafult switch in azid v1.9: -L -3db, and if there's no LFE channel , will it have any negetive affect on the result?

It will have no effect since there is no LFE channel in the AC3 2-ch.

[Moti172]

Thank you