Recommended LC-AAC 5.1 quality setting?

Winston_Smith_101 · 22nd October 2016, 21:49

I would like to transcode lossless 5.1 DTS-HD and Dolby TrueHD Audio into lossy 5.1 LC-AAC (Nero AAC Codec) to save space. What -q quality setting would still sound transparent at your experience?

Wikipedia:

Quote:

Tests of MPEG-4 audio have shown that AAC meets the requirements referred to as "transparent" for the ITU at 128 kbit/s for stereo, and 320 kbit/s for 5.1 audio.

Does that mean you would recommend -q 0.3?

SeeMoreDigital · 22nd October 2016, 22:19

Is there any particular reason why you don't want to use HE-AAC?

Winston_Smith_101 · 22nd October 2016, 22:52

Quote:

Originally Posted by SeeMoreDigital

Is there any particular reason why you don't want to use HE-AAC?

Yes, there is a reason. HE-AAC uses "Spectral band replication" (SBR). Since SBR generates high frequencies only synthetically, no transparency can be achieved with HE-AAC in contrast to LC-AAC.

lvqcl · 22nd October 2016, 23:16

As far as I remember, neroaacenc -q 0.3 creates HE-AAC files (avg. bitrate is ~84 kbps for stereo files).

kuchikirukia · 23rd October 2016, 05:14

QAAC q63 or higher. If you're not looking to skimp, q91 and q109 are popular settings.

Winston_Smith_101 · 23rd October 2016, 09:28

@lvqcl: You are absolutely right. I meant q 0.4. I was so tired last evening, I have not remembered the exact number. 0.3 is to low.

@kuchikirukia: Thank you! I did not know QAAC at all. After what I could read the Apple AAC codec is really better than Nero AAC. I am not looking to skimp, i am looking for high quality transparent sound without wasting space. I will try that q91 and above settings.

You guys helped me a lot!

tebasuna51 · 23rd October 2016, 10:57

Use q91 TVBR (-V 91) with QAAC is, more or less, equivalent to use -q 0.5 with NeroAacEnc.

QAAC is better than NeroAacEnc at low bitrates, at high quality like this can't be tested, both are transparent.

In my test I obtain 450 Kb/s (-V 91 qaac) and 443 Kb/s (-q 0.5 Nero) with the same 5.1 sample.

If you want 320 Kb/s you can try the CVBR mode with QAAC -v 320 (v lowcase)

With the same sample I obtain:

Code:

Nero      5.1-48  |  Qaac    5.1-48
------   -------- | ------  --------
q 0.35   266 Kb/s | -V 54    277 Kb/s
                  | -V 64    314 Kb/s
q 0.4    325 Kb/s | -V 73    351 Kb/s
                  | -V 82    385 Kb/s
q 0.5    443 Kb/s | -V 91    450 Kb/s
                  | -V 99    507 Kb/s
q 0.6    545 Kb/s | -V 109   581 Kb/s
                  | -V 118   638 Kb/s
q 0.7    738 Kb/s | -V 125   704 Kb/s
q 0.8    796 Kb/s |
q 0.9    914 Kb/s |

Of course quality mode can obtain different bitrates with different samples.

22nd October 2016, 22:19	#2 \| Link
SeeMoreDigital Life's clearer in 4K UHD Join Date: Jun 2003 Location: Notts, UK Posts: 12,227	Is there any particular reason why you don't want to use HE-AAC? __________________ \| I've been testing hardware media playback devices and software A/V encoders and decoders since 2001 \| My Network Layout & A/V Gear \|

23rd October 2016, 05:14	#5 \| Link
kuchikirukia Registered User Join Date: Oct 2014 Posts: 476	QAAC q63 or higher. If you're not looking to skimp, q91 and q109 are popular settings. Last edited by kuchikirukia; 23rd October 2016 at 05:29.

23rd October 2016, 10:57	#7 \| Link
tebasuna51 Moderator Join Date: Feb 2005 Location: Spain Posts: 6,915	Use q91 TVBR (-V 91) with QAAC is, more or less, equivalent to use -q 0.5 with NeroAacEnc. QAAC is better than NeroAacEnc at low bitrates, at high quality like this can't be tested, both are transparent. In my test I obtain 450 Kb/s (-V 91 qaac) and 443 Kb/s (-q 0.5 Nero) with the same 5.1 sample. If you want 320 Kb/s you can try the CVBR mode with QAAC -v 320 (v lowcase) With the same sample I obtain: Code: Nero 5.1-48 \| Qaac 5.1-48 ------ -------- \| ------ -------- q 0.35 266 Kb/s \| -V 54 277 Kb/s \| -V 64 314 Kb/s q 0.4 325 Kb/s \| -V 73 351 Kb/s \| -V 82 385 Kb/s q 0.5 443 Kb/s \| -V 91 450 Kb/s \| -V 99 507 Kb/s q 0.6 545 Kb/s \| -V 109 581 Kb/s \| -V 118 638 Kb/s q 0.7 738 Kb/s \| -V 125 704 Kb/s q 0.8 796 Kb/s \| q 0.9 914 Kb/s \| Of course quality mode can obtain different bitrates with different samples. __________________ BeHappy, AviSynth audio transcoder. Last edited by tebasuna51; 23rd October 2016 at 11:13. Reason: add info

22nd October 2016, 23:16	#4 \| Link
lvqcl Registered User Join Date: Aug 2015 Posts: 294	As far as I remember, neroaacenc -q 0.3 creates HE-AAC files (avg. bitrate is ~84 kbps for stereo files).

23rd October 2016, 09:28	#6 \| Link
Winston_Smith_101 Registered User Join Date: Sep 2016 Posts: 16	@lvqcl: You are absolutely right. I meant q 0.4. I was so tired last evening, I have not remembered the exact number. 0.3 is to low. @kuchikirukia: Thank you! I did not know QAAC at all. After what I could read the Apple AAC codec is really better than Nero AAC. I am not looking to skimp, i am looking for high quality transparent sound without wasting space. I will try that q91 and above settings. You guys helped me a lot!