Reencoding a AC3 to AAC lead to bigger size

[Forteen88]

I don't get it, when I reencoding a AC3 to AAC it resulted in a bigger size than the source (AC3) :P This has not happened before when I've converted AC3 to AAC.
Source was: AC3, English, 5.1 channels, 448kbps, 48khz, dialnorm: -27dB
Anyone who knows why?

eac3to v3.22
command line: C:\Utils\eac3to_v3.22\eac3to.exe "C:\Videos\Planet Earth - The Complete Series HD-DVD 1080p VC-1 DD.5.1\DiSC 2\HVDVD_TS\PEVOB001.EVO" 3: Planet Earth EP04.aac
Which means that quality=0.5

Thanks

[nurbs]

Source was: AC3, English, 5.1 channels, 448kbps, 48khz, dialnorm: -27dB
Yes and no. That AC3 track was the source you decoded, but the source you encoded was an uncompressed 5.1 48 kHz PCM track (4.6 Mbps assuming 16 bit). Nero looked at that PCM track and decided that a certain bitrate was required to achieve the quality you wanted. That bitrate was higher than the AC3 bitrate, but NeroAAC never knew about the AC3 to begin with.

[Blue_MiSfit]

I'd say that over 448kbps isn't unusual for -quality=0.50.

If you want a specific bitrate, force is by replacing -quality=x with -x.

Also, nurbs hit the nail on the head. Neroaacenc has no notion of your source being AC3. It sees uncompressed PCM, since the flow goes like this:

AC3---(libavcodec)--->PCM---(neroaacenc)--->AAC

I usually keep 448kbps AC3s as-is. To me, the tiny reduction availble from going to ~200-300kbps 6ch AAC isn't usually worth it.

Derek

[nibus]

To save any space you might want to go as low as 0.4. That's what I usually encode 5.1 audio to if I'm looking to save space. It's usually somewhere around 350kbps, and to my ears sounds pretty close to the source.