AAC cannot go below 32

[TheJ]

So as of recently i have been messing around with FFmpeg and i noticed with their AAC encoder can go below 32k, which really surprised me since i dont know that was possible. So i checked in hybrid to my surprise you cant, even though after turning on the FDK option, why?

[Selur]

Simple:
a. I had/have no documentaion that sais the encoder can go below that and I did not test, since I don't use such low bit rates.
b. show me some documentation with which settings the encoder supports lower bit rates and which and I can add support for it.
Importen parameters for aac encoders are:
a. lc-aac/he-aac/he-aacv2
b. encoding mode (abr/vbr/..)
c. sample rate

-> show me some documentation or do the tests and document them and I can add support for it.

For qaac I got:

LC 8000Hz Mono -- 8,12,16,20,24
LC 8000Hz Stereo (L R) -- 16,20,24,28,32,40,48
LC 8000Hz Quadrophonisch -- 32,40,48,56,64,72,80,96
LC 8000Hz 4.0 (C L R Cs) -- 32,40,48,56,64,72,80,96
LC 8000Hz 5.0 (C L R Ls Rs) -- 40,48,56,64,72,80,96,112
LC 8000Hz 5.1 (C L R Ls Rs LFE) -- 40,48,56,64,72,80,96,112
LC 8000Hz 6.0 (C L R Ls Rs Cs) -- 48,56,64,72,80,96,112,128,144
LC 8000Hz 6.1 (C L R Ls Rs Cs LFE) -- 48,56,64,72,80,96,112,128,144
LC 8000Hz 7.0 (C L R Ls Rs Rls Rrs) -- 56,64,72,80,96,112,128,144,160
LC 8000Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 56,64,72,80,96,112,128,144,160
LC 8000Hz 8.0 (C L R Ls Rs Rls Rrs Cs) -- 64,72,80,96,112,128,144,160,192
LC 11025Hz Mono -- 8,12,16,20,24,28,32
LC 11025Hz Stereo (L R) -- 16,20,24,28,32,40,48,56,64
LC 11025Hz Quadrophonisch -- 48,56,64,72,80,96,112,128
LC 11025Hz 4.0 (C L R Cs) -- 48,56,64,72,80,96,112,128
LC 11025Hz 5.0 (C L R Ls Rs) -- 64,72,80,96,112,128,144,160
LC 11025Hz 5.1 (C L R Ls Rs LFE) -- 64,72,80,96,112,128,144,160
LC 11025Hz 6.0 (C L R Ls Rs Cs) -- 72,80,96,112,128,144,160,192
LC 11025Hz 6.1 (C L R Ls Rs Cs LFE) -- 72,80,96,112,128,144,160,192
LC 11025Hz 7.0 (C L R Ls Rs Rls Rrs) -- 96,112,128,144,160,192,224
LC 11025Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 96,112,128,144,160,192,224
LC 11025Hz 8.0 (C L R Ls Rs Rls Rrs Cs) -- 96,112,128,144,160,192,224,256
LC 12000Hz Mono -- 12,16,20,24,28,32
LC 12000Hz Stereo (L R) -- 24,28,32,40,48,56,64
LC 12000Hz Quadrophonisch -- 48,56,64,72,80,96,112,128
LC 12000Hz 4.0 (C L R Cs) -- 48,56,64,72,80,96,112,128
LC 12000Hz 5.0 (C L R Ls Rs) -- 64,72,80,96,112,128,144,160
LC 12000Hz 5.1 (C L R Ls Rs LFE) -- 64,72,80,96,112,128,144,160
LC 12000Hz 6.0 (C L R Ls Rs Cs) -- 72,80,96,112,128,144,160,192
LC 12000Hz 6.1 (C L R Ls Rs Cs LFE) -- 72,80,96,112,128,144,160,192
LC 12000Hz 7.0 (C L R Ls Rs Rls Rrs) -- 96,112,128,144,160,192,224
LC 12000Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 96,112,128,144,160,192,224
LC 12000Hz 8.0 (C L R Ls Rs Rls Rrs Cs) -- 96,112,128,144,160,192,224,256
LC 16000Hz Mono -- 12,16,20,24,28,32,40,48
LC 16000Hz Stereo (L R) -- 24,28,32,40,48,56,64,72,80,96
LC 16000Hz Quadrophonisch -- 48,56,64,72,80,96,112,128,144,160,192
LC 16000Hz 4.0 (C L R Cs) -- 48,56,64,72,80,96,112,128,144,160,192
LC 16000Hz 5.0 (C L R Ls Rs) -- 64,72,80,96,112,128,144,160,192,224
LC 16000Hz 5.1 (C L R Ls Rs LFE) -- 64,72,80,96,112,128,144,160,192,224
LC 16000Hz 6.0 (C L R Ls Rs Cs) -- 72,80,96,112,128,144,160,192,224,256,288
LC 16000Hz 6.1 (C L R Ls Rs Cs LFE) -- 72,80,96,112,128,144,160,192,224,256,288
LC 16000Hz 7.0 (C L R Ls Rs Rls Rrs) -- 96,112,128,144,160,192,224,256,288,320
LC 16000Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 96,112,128,144,160,192,224,256,288,320
LC 16000Hz 8.0 (C L R Ls Rs Rls Rrs Cs) -- 96,112,128,144,160,192,224,256,288,320,384
LC 22050Hz Mono -- 16,20,24,28,32,40,48,56,64
LC 22050Hz Stereo (L R) -- 32,40,48,56,64,72,80,96,112,128
LC 22050Hz Quadrophonisch -- 64,72,80,96,112,128,144,160,192,224,256
LC 22050Hz 4.0 (C L R Cs) -- 64,72,80,96,112,128,144,160,192,224,256
LC 22050Hz 5.0 (C L R Ls Rs) -- 80,96,112,128,144,160,192,224,256,288,320
LC 22050Hz 5.1 (C L R Ls Rs LFE) -- 80,96,112,128,144,160,192,224,256,288,320
LC 22050Hz 6.0 (C L R Ls Rs Cs) -- 96,112,128,144,160,192,224,256,288,320,384
LC 22050Hz 6.1 (C L R Ls Rs Cs LFE) -- 96,112,128,144,160,192,224,256,288,320,384
LC 22050Hz 7.0 (C L R Ls Rs Rls Rrs) -- 112,128,144,160,192,224,256,288,320,384,448
LC 22050Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 112,128,144,160,192,224,256,288,320,384,448
LC 22050Hz 8.0 (C L R Ls Rs Rls Rrs Cs) -- 128,144,160,192,224,256,288,320,384,448,512
LC 24000Hz Mono -- 16,20,24,28,32,40,48,56,64
LC 24000Hz Stereo (L R) -- 32,40,48,56,64,72,80,96,112,128
LC 24000Hz Quadrophonisch -- 64,72,80,96,112,128,144,160,192,224,256
LC 24000Hz 4.0 (C L R Cs) -- 64,72,80,96,112,128,144,160,192,224,256
LC 24000Hz 5.0 (C L R Ls Rs) -- 80,96,112,128,144,160,192,224,256,288,320
LC 24000Hz 5.1 (C L R Ls Rs LFE) -- 80,96,112,128,144,160,192,224,256,288,320
LC 24000Hz 6.0 (C L R Ls Rs Cs) -- 96,112,128,144,160,192,224,256,288,320,384
LC 24000Hz 6.1 (C L R Ls Rs Cs LFE) -- 96,112,128,144,160,192,224,256,288,320,384
LC 24000Hz 7.0 (C L R Ls Rs Rls Rrs) -- 112,128,144,160,192,224,256,288,320,384,448
LC 24000Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 112,128,144,160,192,224,256,288,320,384,448
LC 24000Hz 8.0 (C L R Ls Rs Rls Rrs Cs) -- 128,144,160,192,224,256,288,320,384,448,512
LC 32000Hz Mono -- 24,28,32,40,48,56,64,72,80,96
LC 32000Hz Stereo (L R) -- 48,56,64,72,80,96,112,128,144,160,192
LC 32000Hz Quadrophonisch -- 96,112,128,144,160,192,224,256,288,320,384
LC 32000Hz 4.0 (C L R Cs) -- 96,112,128,144,160,192,224,256,288,320,384
LC 32000Hz 5.0 (C L R Ls Rs) -- 128,144,160,192,224,256,288,320,384,448
LC 32000Hz 5.1 (C L R Ls Rs LFE) -- 128,144,160,192,224,256,288,320,384,448
LC 32000Hz 6.0 (C L R Ls Rs Cs) -- 144,160,192,224,256,288,320,384,448,512,576
LC 32000Hz 6.1 (C L R Ls Rs Cs LFE) -- 144,160,192,224,256,288,320,384,448,512,576
LC 32000Hz 7.0 (C L R Ls Rs Rls Rrs) -- 192,224,256,288,320,384,448,512,576,640
LC 32000Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 192,224,256,288,320,384,448,512,576,640
LC 32000Hz 8.0 (C L R Ls Rs Rls Rrs Cs) -- 192,224,256,288,320,384,448,512,576,640,768
LC 44100Hz Mono -- 32,40,48,56,64,72,80,96,112,128,144,160,192,224,256
LC 44100Hz Stereo (L R) -- 64,72,80,96,112,128,144,160,192,224,256,288,320
LC 44100Hz Quadrophonisch -- 128,144,160,192,224,256,288,320,384,448,512,576,640
LC 44100Hz 4.0 (C L R Cs) -- 128,144,160,192,224,256,288,320,384,448,512,576,640
LC 44100Hz 5.0 (C L R Ls Rs) -- 160,192,224,256,288,320,384,448,512,576,640,768
LC 44100Hz 5.1 (C L R Ls Rs LFE) -- 160,192,224,256,288,320,384,448,512,576,640,768
LC 44100Hz 6.0 (C L R Ls Rs Cs) -- 192,224,256,288,320,384,448,512,576,640,768,960
LC 44100Hz 6.1 (C L R Ls Rs Cs LFE) -- 192,224,256,288,320,384,448,512,576,640,768,960
LC 44100Hz 7.0 (C L R Ls Rs Rls Rrs) -- 224,256,288,320,384,448,512,576,640,768,960
LC 44100Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 224,256,288,320,384,448,512,576,640,768,960
LC 44100Hz 8.0 (C L R Ls Rs Rls Rrs Cs) -- 256,288,320,384,448,512,576,640,768,960,1280
LC 48000Hz Mono -- 32,40,48,56,64,72,80,96,112,128,144,160,192,224,256
LC 48000Hz Stereo (L R) -- 64,72,80,96,112,128,144,160,192,224,256,288,320
LC 48000Hz Quadrophonisch -- 128,144,160,192,224,256,288,320,384,448,512,576,640
LC 48000Hz 4.0 (C L R Cs) -- 128,144,160,192,224,256,288,320,384,448,512,576,640
LC 48000Hz 5.0 (C L R Ls Rs) -- 160,192,224,256,288,320,384,448,512,576,640,768
LC 48000Hz 5.1 (C L R Ls Rs LFE) -- 160,192,224,256,288,320,384,448,512,576,640,768
LC 48000Hz 6.0 (C L R Ls Rs Cs) -- 192,224,256,288,320,384,448,512,576,640,768,960
LC 48000Hz 6.1 (C L R Ls Rs Cs LFE) -- 192,224,256,288,320,384,448,512,576,640,768,960
LC 48000Hz 7.0 (C L R Ls Rs Rls Rrs) -- 224,256,288,320,384,448,512,576,640,768,960
LC 48000Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 224,256,288,320,384,448,512,576,640,768,960
LC 48000Hz 8.0 (C L R Ls Rs Rls Rrs Cs) -- 256,288,320,384,448,512,576,640,768,960,1280
HE 32000Hz Mono -- 12,16,24,32,40
HE 32000Hz Stereo (L R) -- 24,32,40,48,56,64,80
HE 32000Hz Quadrophonisch -- 48,56,64,80,96,112,128,160
HE 32000Hz 5.1 (C L R Ls Rs LFE) -- 64,80,96,112,128,160,192
HE 32000Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 96,112,128,160,192,224,256
HE 44100Hz Mono -- 16,24,32,40
HE 44100Hz Stereo (L R) -- 32,40,48,56,64,80
HE 44100Hz Quadrophonisch -- 64,80,96,112,128,160
HE 44100Hz 5.1 (C L R Ls Rs LFE) -- 80,96,112,128,160,192
HE 44100Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 112,128,160,192,224,256
HE 48000Hz Mono -- 16,24,32,40
HE 48000Hz Stereo (L R) -- 32,40,48,56,64,80
HE 48000Hz Quadrophonisch -- 64,80,96,112,128,160
HE 48000Hz 5.1 (C L R Ls Rs LFE) -- 80,96,112,128,160,192
HE 48000Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 112,128,160,192,224,256
HE 88200Hz Mono -- 32,40,48,56,64,80,96,112,128,160
HE 88200Hz Stereo (L R) -- 64,80,96,112,128,160,192,224,256,320
HE 88200Hz Quadrophonisch -- 128,160,192,224,256,320,448,640
HE 88200Hz 5.1 (C L R Ls Rs LFE) -- 160,192,224,256,320,448,640
HE 88200Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 224,256,320,448,640,1120
HE 96000Hz Mono -- 32,40,48,56,64,80,96,112,128,160
HE 96000Hz Stereo (L R) -- 64,80,96,112,128,160,192,224,256,320
HE 96000Hz Quadrophonisch -- 128,160,192,224,256,320,448,640
HE 96000Hz 5.1 (C L R Ls Rs LFE) -- 160,192,224,256,320,448,640
HE 96000Hz 7.1 (C Lc Rc L R Ls Rs LFE) -- 224,256,320,448,640,1120

Cu Selur

[b0red]

So as of recently i have been messing around with FFmpeg and i noticed with their AAC encoder can go below 32k, which really surprised me since i dont know that was possible. So i checked in hybrid to my surprise you cant, even though after turning on the FDK option, why?

Because there is no point for a video re-encoder like Hybrid?

AAC starts sucking with lower bitrates so they invented AAC-HE(+/v1/v2) for DAB+ radios /car head units to limit data as much as possible. As can be seen in qaac's Shittime wrapper specs the <32k bitrates are only for reduced sample rates (designed for talkback radio mostly).

For extra ridiculousness: none of my 4 DAB+ radio/head units can playback AAC audio in a file.

The rest of the non-proprietary format world moved to using Opus.

[TheJ]

So as of recently i have been messing around with FFmpeg and i noticed with their AAC encoder can go below 32k, which really surprised me since i dont know that was possible. So i checked in hybrid to my surprise you cant, even though after turning on the FDK option, why?

Because there is no point for a video re-encoder like Hybrid?

AAC starts sucking with lower bitrates so they invented AAC-HE(+/v1/v2) for DAB+ radios /car head units to limit data as much as possible. As can be seen in qaac's Shittime wrapper specs the <32k bitrates are only for reduced sample rates (designed for talkback radio mostly).

For extra ridiculousness: none of my 4 DAB+ radio/head units can playback AAC audio in a file.

The rest of the non-proprietary format world moved to using Opus.

"AAC starts sucking with lower bitrates"
which is exactly the point, to fit 8mb videos on Discord

[b0red]

The rest of the non-proprietary format world moved to using Opus.

"AAC starts sucking with lower bitrates"
which is exactly the point, to fit 8mb videos on Discord

Discord uses Opus as it's default audio codec (specifically a sub 64kbps subset from memory), ditto for WebM videos (which hybrid can also make). It performs better at low bitrates than AAC.
Not specifically sure if every version of discord plays videos the same but all the modern web browsers and OS's discord runs on have it either built-in or support it.

[TheJ]

The rest of the non-proprietary format world moved to using Opus.

"AAC starts sucking with lower bitrates"
which is exactly the point, to fit 8mb videos on Discord

Discord uses Opus as it's default audio codec (specifically a sub 64kbps subset from memory), ditto for WebM videos (which hybrid can also make). It performs better at low bitrates than AAC.
Not specifically sure if every version of discord plays videos the same but all the modern web browsers and OS's discord runs on have it either built-in or support it.

Opus at very low bitrates sound extremely distorted, you can't even hear anything. AAC on the other hand sounds muffled but you can make out the sound of it