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Started by guju, May 30, 2023, 04:25:22 PM

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mp4 (avc1, aac-VBR) seems to be an common combination.
I would like to do that too.

Is there a reason why there's no aac VBR in AVIDemux?
(If I get it right AVIDemux' internal audio codes with VBR are:
vorbis (outdated), mp3 (lame) and opus (?).
But these seem "unusal" in combination with mp4/ avc1?).

Please advice.


AAC is always VBR.


You find me confused...

Maybe a misunderstanding?

Most of the public accessable movie from a TV station here have - as said - aac vbr -
but some of them are like this (Copied from MediaInfo):

ID                          : 2
Format                      : AAC LC
Format/Info                : Advanced Audio Codec Low Complexity
Codec ID                    : mp4a-40-2
Duration                    : 1 h 56 min
Bit rate mode              : Constant
Bit rate                    : 160 kb/s
Channel(s)                  : 2 channels
Channel layout              : L R
Sampling rate              : 48.0 kHz
Frame rate                  : 46.875 FPS (1024 SPF)
Compression mode            : Lossy
Stream size                : 134 MiB (4%)


In AAC CBR is more like an average bitrate, whereas VBR is a quality mode. Typically for videos you would use CBR.

Constant Bit Rate (CBR) mode
These settings target a specific bit rate, with less variation between samples. It gives you greater control over file size [...] As a rule of thumb, for audible transparency, use 64 kBit/s for each channel (so 128 kBit/s for stereo, 384 kBit/s for 5.1 surround sound).

Variable Bit Rate (VBR) mode
Target a quality, rather than a specific bit rate. 1 is lowest quality and 5 is highest quality. 


Pardon, but that sounds quite strange to me.

When an AAC is labelled as CBR it is actually ABR?
(Why don't the call it ABR then?)
While true CBR in AAC doesn't exist.
And AviDemux generates AAC only as ABR (which is called CBR then)?
No way to generate true AAC VBR with AviDemux?
(While - as stated - most prof movies use AAC VBR).

Is that the way things are? Or do I got something wrong?