What is the --mode= command for R3 high quality aac streams please

[richard]

On Thu Jun 16 10:17:33 bat guano wrote:

> I don't know anything about FFmpeg's internal "experimental" aac 
> encoder.
>
> But libfaac is based on faac encoder.
> faac is a VBR encoder.
>
> Using faac --long-help shows:-
> -q <quality>    Set default variable bitrate (VBR) quantizer quality 
> in percent.
>        (default: 100, averages at approx. 120 kbps VBR for a normal
>        stereo input file with 16 bit and 44.1 kHz sample rate; max.
>        value 500, min. 10).
>
> So -aq <quality> is used with FFmpeg libfaac to set the quantizer 
> quality of the VBR.
> 
> When -ab <bitrate> is used with FFmpeg libfaac it sets the ABR.
> (That's the average bitrate of the variable bitrate).
>
> Using faac --long-help shows:-
> -b <bitrate>    Set average bitrate (ABR) to approximately <bitrate> 
> kbps.
>        (max. value 152 kbps/stereo with a 16 kHz cutoff, can be raised
>        with a higher -c setting).
>
> It seems the ABR is capped at 152Kbps unless that value "c" is 
> changed.
> I'm not sure how to change that "c" value with FFmpeg, or even how to
> calculate a suitable value for it.

Hi bat

Thanks for the info on faac. I'm also not familiar with ffmpeg's
experimental aac encoder. Found it by accident. It seems to have a
higher bitrate cap than libfaac.

Re-encoding with libfaac using VBR option -aq 500 (the max value): 

ffmpeg -i input.flv -acodec libfaac -aq 500 output.m4a

produced an m4a file at 264kbps.

I assume the higher -c setting refers to the frequency setting. 
faac --long-help shows:

-c <freq> Set the bandwidth in Hz (default: automatic, i.e. adapts
maximum value to input sample rate).

Not sure if ffmpeg's libfaac uses the -c option. When I tried, it
aborted with error unrecognized option 'c'.