AAC audio and bitrate

[David1105]

Is it possible at all for an AAC audio file to be of Constant Bit Rate (CBR), instead of VBR or ABR? Reading info from various sources inidcates different things to me so far...

Why MediaInfo always displays output AAC audio file as VBR if using FFMPEG with libfaac codec?

If possible at all for to config libfaac to output CBR? Or does anyone have a build of libfaac codec which support CBR?

[microchip8]

Originally Posted by David1105

Is it possible at all for an AAC audio file to be of Constant Bit Rate (CBR), instead of VBR or ABR? Reading info from various sources inidcates different things to me so far...

Why MediaInfo always displays output AAC audio file as VBR if using FFMPEG with libfaac codec?

If possible at all for to config libfaac to output CBR? Or does anyone have a build of libfaac codec which support CBR?

Yes, it is possible for AAC to use CBR mode. Not all encoders support CBR mode though. One of which supports it is neroAacEnc through the -cbr option

MediaInfo displays VBR because FAAC only encodes in VBR. It does not support CBR encodings

[David1105]

Originally Posted by froggy1

Yes, it is possible for AAC to use CBR mode. Not all encoders support CBR mode though. One of which supports it is neroAacEnc through the -cbr option

I tried also with neroAacEnc with the following

neroaacenc -br 1 -cbr 128000 -if input.wav -of output.m4a

But MediaInfo still says:

Bit rate mode : Variable
Bit rate : 128 Kbps

[microchip8]

Originally Posted by David1105

I tried also with neroAacEnc with the following

neroaacenc -br 1 -cbr 128000 -if input.wav -of output.m4a

But MediaInfo still says:

Bit rate mode : Variable
Bit rate : 128 Kbps

it should be neroAacEnc -cbr 128000 -if input.wav -of output.m4a

you cannot mix both -br and -cbr. You can either use quality-based encoding (-q), ABR-based encoding (-br) or CBR-based encoding (-cbr)

if MediaInfo still shows its VBR, then there's something wrong with it

[David1105]

Originally Posted by froggy1

it should be neroAacEnc -cbr 128000 -if input.wav -of output.m4a

you cannot mix both -br and -cbr. You can either use quality-based encoding (-q), ABR-based encoding (-br) or CBR-based encoding (-cbr)

if MediaInfo still shows its VBR, then there's something wrong with it

I tried without -br again, and MediaInfo displays the same.

Wrong with what? MediaInfo or neroAacEnc?

[microchip8]

Originally Posted by David1105

I tried without -br again, and MediaInfo displays the same.

Wrong with what? MediaInfo or neroAacEnc?

MediaInfo

[nurbs]

IIRC cbr in aac is never truly cbr, but vbr with a very small buffer size. The nero guys discussed this on hydrogenaudio.org and if you search there I am sure you can find a good explaination.