AAC file larger then original AC3

[Surye]

Using MeGUI as a front-end to neroaacenc.exe (SSE2 build) I encoded 2 ac3 files ripped from a DVD source using defaults.

First File:
2ch AC3@192kbits - 143,898,624 bytes
2ch AAC@Q0.5 - 87,922,276 bytes

Second File:
6ch AC3@448kbits - 335,763,456 bytes
6ch AAC@Q0.5 - 398,769,575 bytes

The second file is my concern. Why should this file indeed be larger then the source audio? Are there any other benifits to AAC that out wiegh size in this case (AC3 Passthru is a big negative), or am I just doing something wrong?

Thanks for any help.

[Turneliusz]

I think you've just set too high quality for encoded aac. Try with lower Q parameter.

Here you have an example of bitrate-quality relations for 2ch source:
Bitrate->Quality
15----->0.05
32----->0.15
63----->0.25
99----->0.35
146---->0.45
197---->0.55
248---->0.65
299---->0.75
350---->0.85
401---->0.95

[JarrettH]

Same problem!

Belight resamples.....why?

megui nero/aac creates larger files.....why should I have to lower it until it makes it smaller? 0.55 is almost default

[check]

I think you're a bit confused about how the 'quality' switch works. When you increase the quality level you increase the bitrate of the audio output and therefore the size of the file. If you wish to reduce filesize you need to reduce bitrate and hence reduce quality.

[JarrettH]

I know, but it's supposed to compress. I don't want to keep 5.1 audio with a lousy bitrate.

Why does belight resample my audio too? Would using SSRC to make it 48khz be redundant?

[GodofaGap]

Uhm, you forget that you that the AC3 needs to be uncompressed to compress again. The codec thinks it is compressing a 4608 kbps PCM file, not a 448 kbps AC3 file (because it obviously cannot make sense out of compressed AC3 data).

The quality switch is not in any way related to the original bitrate of your compressed source.

[JarrettH]

Ooooo thanks Godofa!!:thanks:

[JarrettH]

Giving me error when I try to go wav ---> aac:eek:


Looks like wav can't be over 2gb. So everyone must transcode this stuff?