AAC not encoding at specified CBR bitrate

[killerteengohan]

Normally this works fine, but for this particular Blu-Ray set, it will not encode the audio at the bitrate I specified.

I am using MeGui with neroaacenc like I always have. For whatever reason, when I try to encode the audio to 576kbps or 640kbps, no matter what, it caps at, and stays at 562kbps. I have even tried multiple versions of MeGui and they all give the same results. Whats up with this, and why is it not encoding at the specified bitrate? Just about every other Blu-Ray I have encoded the audio from came out the CBR bitrate I specified.

The DTS audio says its over 1500kbps and the FLAC version extraction says its 647kbps so why cant I get it to be 576kbps or 640kbps when encoding to AAC like I usually can?

[voau]

...so why cant I get it to be 576kbps or 640kbps when encoding to AAC like I usually can?

It seems the encoder is saturated. It simply cannot encode the audio in question with a better quality, it already did its best and did not need the extra bits.

To make things easier to understand, it is like encoding a 1411 kbps PCM to a 1500 kbps AAC (the extra bits you provided will be useless).

[killerteengohan]

I understand what you're saying without the example. I never heard of an audio codec or encoder not allowing you to use or waste bits if you want.

I found out what the issue was though. I thought the audio was 5.1 surround, and its only 2.0 stereo. I never tried making 2.0 stereo more than 256kbps. I think that might have been the reason, and you telling me about the encoder being able to know when too much is too much, sent me in the right direction to check.

Thanks for the answer and info!

[jagabo]

I never heard of an audio codec or encoder not allowing you to use or waste bits if you want.

It's very common. Also at the other end -- if you request too low a bitrate the encoder may not be able to achieve it.