Quote:
Originally Posted by tebasuna51
Is not possible. For a 2-pass AAC encode you need a physical wav file.
You can decode the source to wav and after use the NeroAacEnc CLI.
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Ok, thanks.
I will share an info that might be useful to someone...
I encoded a 448kbps 5.1ch AC3 with
eac3to input.ac3 output.m4a -quality=0.3 and this is what media info says about the output.m4a file:
-------------------------------
Audio
ID : 1
Format : AAC
Format/Info : Advanced Audio Codec
Format version : Version 4
Format profile : LC
Format settings, SBR : Yes
Format settings, PS : No
Codec ID : 40
Duration : 3h 13mn
Bit rate mode : Variable
Bit rate : 222 Kbps
Maximum bit rate : 308 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Stream size : 307 MiB (100%)
Encoded date : UTC 2010-10-11 14:12:01
Tagged date : UTC 2010-10-11 14:25:42
-------------------------------
So, for this particular source (will change from source to source), -q 0.3 resulted in a 222kbps 5.1ch AAC file. Note that it is using SBR, so I guess this would be an AAC-HE, instead of AAC-LC.
I did some blind test, switching between the 448kbps AC3 and the 222kbps AAC. They sound pretty much the same, with a tiny advantage for the AC3 file, pretty much negligible, very hard to detect.
So, I would recomend AAC with -q ~0.3 for 5.1ch audio. This will save space, and will give you the chance to raise your video bitrate for more image quality too.
I have only tested -q 0.3 with 5.1ch movie audio tracks. I don't know about stereo or music audio tracks, but I would imagine that for stereo music, -q 0.3 might not be enough, you might wanna use -q 0.35 or even higher values for stereo music tracks.