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Topic: What's the best lossy codec for multichannel audio (Read 10741 times) previous topic - next topic
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What's the best lossy codec for multichannel audio

Hi folks,

I've got a bunch of DTS CDs and I am looking for a decent codec to transcode the stuff. I found some threads about issues like channel coupling and other issues that are important for multi-channel files but I haven't found test comparing different codecs with each other.

Obvious choices are:

- Ogg Vorbis
- (He-)AAC
- WMA

The main purpose I'd like to transcode the stuff is for saving disk space, because I'm a poor student  Furthermore, I would like to use foobar2000 for conversion for the sake of simplicity.

I definitly don't consider myself to be an audiophile (lame aps is more than enougth for me for 2channel files) but I wouldn't like to transcode everything, and realizing after a couple of months and properply new equiptment that everything is messed up. Another thing I cannot really assess is the necessity of certain bitrates e.g. ac3 definitly does not need a high bitrate as dts does.

I tried a dts test encode for a file and here are my results:

ogg vorbis -q5: 459kbps
lc-aac (transperant setting): 544kbps

I just consider both setting are still a waste of diskspace for me so any ideas?

Chris

What's the best lossy codec for multichannel audio

Reply #1 –
For 5.1 audio I'd go with AAC (not HE) at 320 kbps.

What's the best lossy codec for multichannel audio

Reply #3 –
Quote
At what setting?
[a href="index.php?act=findpost&pid=316197"][{POST_SNAPBACK}][/a]


Just use 320 kbps CBR (constant bitrate), or find out which VBR (variable bitrate) mode will give you bitrate in the range of 300 to 350 kbps.

5.1 bitrate = STEREO + STEREO + MONO + LFE

For AAC it is believed that the following bitrates produce 'transparent' quality for vast majority of audio samples:

STEREO ~ 128 kbps
MONO ~ 80 kbps
LFE < 10 kbps

so

5.1 bitrate ~ 350 kbps.


Daniel

What's the best lossy codec for multichannel audio

Reply #4 –
@dand
it's not that simple

@chris

apart from mp3 surround which is a proprietary codec
aac is at time the only lossy one with channel coupling at multichannel.

you could try he-aac at around 120-170kbit.
personal i don't like the "sbr-sound".
or you go for lc-aac at around 230-320kbit. forget cbr!

at sense of bitrate for me aac is not much better than ac3 for example.

What's the best lossy codec for multichannel audio

Reply #5 –
Quote
it's not that simple

Where did I go wrong?

Quote
you could try he-aac at around 120-170kbit.

HE AAC is NOT to be used for transparency. It will never replace AAC, it is its extension for low bitrates only.

Quote
or you go for lc-aac at around 230-320kbit. forget cbr!

How can you fit two stereo pairs and one mono channel into 230 kbps? That won't give you transparency.

Quote
at sense of bitrate for me aac is not much better than ac3 for example.

Not true. AAC outperformes AC3 at any bitrate.

What's the best lossy codec for multichannel audio

Reply #6 –
Quote
Where did I go wrong?


with your simple equation 128+128+80+10=transparent

Quote
HE AAC is NOT to be used for transparency. It will never replace AAC, it is its extension for low bitrates only.


chris did not mentioned the word 'transparent' anywhere except for
the preset. i understood the question as a call for low bitrate encodings.

Quote
How can you fit two stereo pairs and one mono channel into 230 kbps? That won't give you transparency.


ever monitored a 5.1 recording? not every channel is always peaked out
to the max. or you get the same signal shifted through 4 channels etc...
do you know how good the coupling inside aac works?
test for yourself...i don't consider myself an audiophile.
i can even live with a 140kbit 5.1 he-aac file.


Quote
Not true. AAC outperformes AC3 at any bitrate.


abx tests? or is this your personal opinion?

What's the best lossy codec for multichannel audio

Reply #7 –
Quote
Quote
Not true. AAC outperformes AC3 at any bitrate.
abx tests? or is this your personal opinion?[a href="index.php?act=findpost&pid=316212"][{POST_SNAPBACK}][/a]


I believe that can be inferred from a math point of view alone. It's well known around here that, from an algorithmic point of view, AC3 is about on par with MP2. So, it isn't (theoretically) even in the same league as MP3, let alone AAC.

What's the best lossy codec for multichannel audio

Reply #8 –
Quote
I believe that can be inferred from a math point of view alone.


that is not the point of this discussion.
it's possible that aac improves on multichannel but in it's current state
of development 320kbit aac is not much less than 448kbit ac3. that's math.

What's the best lossy codec for multichannel audio

Reply #9 –
Quote
Quote
Where did I go wrong?


with your simple equation 128+128+80+10=transparent

Quote
HE AAC is NOT to be used for transparency. It will never replace AAC, it is its extension for low bitrates only.


chris did not mentioned the word 'transparent' anywhere except for
the preset. i understood the question as a call for low bitrate encodings.

Quote
How can you fit two stereo pairs and one mono channel into 230 kbps? That won't give you transparency.


ever monitored a 5.1 recording? not every channel is always peaked out
to the max. or you get the same signal shifted through 4 channels etc...
do you know how good the coupling inside aac works?
test for yourself...i don't consider myself an audiophile.
i can even live with a 140kbit 5.1 he-aac file.


Quote
Not true. AAC outperformes AC3 at any bitrate.


abx tests? or is this your personal opinion?
[a href="index.php?act=findpost&pid=316212"][{POST_SNAPBACK}][/a]


'128+128+80+10=transparent' maybe is a simple equation for you, but there is a huge amount of work done before audio coding got there...

HE AAC should be used for internet radio or your mobile phone, but I don't think that's the case here.

Let's not compare AC3 to AAC, it's not polite.

I never monitored a 5.1 recoding, but I did recently listen to, for example, Beck's Guero as a separate 5.1 album release. Couldn't hear 'same' signal sent to more than 2 channels (and its not the same, only similar, which is a big difference).

Why don't you tell us how AAC handles 6 channels in 5.1 configuration?

What's the best lossy codec for multichannel audio

Reply #10 –
Quote
HE AAC should be used for internet radio or your mobile phone, but I don't think that's the case here.


at my first trys with he-aac it sounded ok to me at 170kbit transcoded from
a 448kbit ac3. but that are just my ears.

Quote
Let's not compare AC3 to AAC, it's not polite.


why not? at high bitrate you did not provide any argument against doing this.

Quote
I never monitored a 5.1 recoding, but I did recently listen to, for example, Beck's Guero as a separate 5.1 album release. Couldn't hear 'same' signal sent to more than 2 channels (and its not the same, only similar, which is a big difference).
Why don't you tell us how AAC handles 6 channels in 5.1 configuration?


i know little about the codec internals but propper coupling of multichannel
is another story than simple stereo.

What's the best lossy codec for multichannel audio

Reply #11 –
'you are wrong but I don't know what's right'... With that kind of attitude you will just confuse people around here.

What's the best lossy codec for multichannel audio

Reply #12 –
I think, pest impiles that there is no such thing as “two stereo pairs + mono”. It's just five channels, and all of them can be coupled together, without splitting in pairs.
Infrasonic Quartet + Sennheiser HD650 + Microlab Solo 2 mk3. 
 

What's the best lossy codec for multichannel audio

Reply #13 –
Quote
Quote
I believe that can be inferred from a math point of view alone.

that is not the point of this discussion.


And what is the point? You asked for proof that "AAC outperformes AC3 at any bitrate.". I gave you mathematical hints that such claim is probably true.

Quote
it's possible that aac improves on multichannel but in it's current state
of development 320kbit aac is not much less than 448kbit ac3. that's math.
[a href="index.php?act=findpost&pid=316214"][{POST_SNAPBACK}][/a]


And what's with 448kbps AC3? What does it matter? The guy is transcoding from DTS, so using AAC at ~300 will be much better than the original bitrate no matter what.

What's the best lossy codec for multichannel audio

Reply #14 –
Quote
I think, pest impiles that there is no such thing as “two stereo pairs + mono”. It's just five channels, and all of them can be coupled together, without splitting in pairs.
[a href="index.php?act=findpost&pid=316300"][{POST_SNAPBACK}][/a]

Try to find a 5.1 recording that doesn't follow the "two stereo pairs + mono + lfe" rule. I haven't seen one. Of course, you can encode anything with AAC. For example, you can make an encoder that would encode stereo as two mono channels, or also 5.1 as 6 mono channels, or you can pair front left with lfe, but that's something no encoder should do.

2.0 channels = STEREO
5.1 channels = STEREO + STEREO + MONO + LFE

What's the best lossy codec for multichannel audio

Reply #15 –
Quote
Try to find a 5.1 recording that doesn't follow the "two stereo pairs + mono + lfe" rule. I haven't seen one.

There are 6 channels recordings following the 2+2+2 setting. The german label MDG has some in its catalog:
http://www.mdg.de/dvde.htm

More about 2+2+2:
http://www.mdg.de/222e.htm#Anchor--2+2-63965
http://www.aes.org/events/118/exhibitorsem...on.cfm?code=ES6

From whay I've read (French classical music magazines), 2+2+2 recordings are really convincing, and more suited for music ("classical" at least) than 5.1 (with optimal recording and mastering for both).

What's the best lossy codec for multichannel audio

Reply #16 –
Quote
Quote
Try to find a 5.1 recording that doesn't follow the "two stereo pairs + mono + lfe" rule. I haven't seen one.

There are 6 channels recordings following the 2+2+2 setting. The german label MDG has some in its catalog:
http://www.mdg.de/dvde.htm

More about 2+2+2:
http://www.mdg.de/222e.htm#Anchor--2+2-63965
http://www.aes.org/events/118/exhibitorsem...on.cfm?code=ES6

From whay I've read (French classical music magazines), 2+2+2 recordings are really convincing, and more suited for music ("classical" at least) than 5.1 (with optimal recording and mastering for both).
[a href="index.php?act=findpost&pid=316432"][{POST_SNAPBACK}][/a]


Thanks Guru. 2+2+2 is something new (for me) and it seems cool.
However, this still is not a 5.1 recording that doesn't follow "stereo + stereo + mono + lfe" rule. This isn't a 5.1 recording at all, this is 6.0 recording as I understand.