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48 kbps AAC Encoders Test - Q1 2006 Edition
JohnV
post Dec 16 2005, 14:41
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QUOTE (Gabriel @ Dec 15 2005, 06:20 PM)
To me 48kbps is a streaming bitrate, and streaming must be cbr. However, it can feature a big buffer if increased decoding delay is acceptable.
*
What should be done with Vorbis in the multiformat 48kbps test then? Wonder what kind of screming and complaintments happen if Vorbis will be used in the managed bitrate mode. I think this should be decided before the AAC test.
My opinion is that compare best AAC-HE (PS?) VBR/CBR/ABR 48kbps against Vorbis VBR 48kbps, anyway this would be streamable in high speed mobile networks.
Or then no VBR for anybody, including Vorbis.

This post has been edited by JohnV: Dec 16 2005, 14:42


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Ivan Dimkovic
post Dec 16 2005, 14:41
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I think Winamp was the only software actually being able to use CT's HE-AAC v2 implementation at 48 kbps?

Also, I don't know if using internal encoders from CT is allowed by their demo software agreements, as well as it wouldn't be in accordance to the usual test policies that software should be publically available.

So, I think Winamp would suit the purpose best.
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IgorC
post Dec 16 2005, 14:45
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QUOTE (Ivan Dimkovic @ Dec 16 2005, 05:41 AM)
So, I think Winamp would suit the purpose best.
*


It should be checked. CD-DA extractor also has a AAC+2 from CT and its very good. I still didnt checked Winamp 5.12 . However imo CD-DA AAC+2 was better than aac+2 from 5.11.
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Ivan Dimkovic
post Dec 16 2005, 15:07
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Can more people confirm this? We would use best we can get.
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Gabriel
post Dec 16 2005, 15:18
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QUOTE
I think Winamp was the only software actually being able to use CT's HE-AAC v2 implementation at 48 kbps?

Helix?

QUOTE
What should be done with Vorbis in the multiformat 48kbps test then? Wonder what kind of screming and complaintments happen if Vorbis will be used in the managed bitrate mode. I think this should be decided before the AAC test.
My opinion is that compare best AAC-HE (PS?) VBR/CBR/ABR 48kbps against Vorbis VBR 48kbps, anyway this would be streamable in high speed mobile networks.
Or then no VBR for anybody, including Vorbis.

I agree that this should be decided before the AAC test.
To me you can only be sure that you can substain the stream in CBR. VBR is only likely to work.
Anyway, if most people here are not interested in the streamability of 48kbps, then use whatever mode is recommended by developpers.
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IgorC
post Dec 16 2005, 15:19
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Does helix support HE-AAC2?
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IgorC
post Dec 16 2005, 15:29
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More probably its the same updated audio encoder in both Winmp 5.12 and CD-DA extractor 9.0.1 from 14 dec. Now both have a same lowpass at 20.5 khz.

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kurtnoise
post Dec 16 2005, 18:33
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QUOTE (IgorC @ Dec 16 2005, 03:19 PM)
Does helix support HE-AAC2?
*

nope only he-aac v1.


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ckjnigel
post Dec 16 2005, 19:43
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I wish very much that someone who can translate Japanese/English will pass along the discussion in this thread to "aoyumi" and the other Japanese Ogg Vorbis developers. They're the carriers of the flame for that format! Double-pass ABR is new to me, but quite possibly they have some experimental builds of that which they could proffer.
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PatchWorKs
post Dec 19 2005, 12:20
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Hey, guyz... be calm.

In my opinion "legal" bitrates are a multiplies of standard one: 128 Kbps

So: 8 16 32 64 128 256...

Anyway just my opinion.
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stephanV
post Dec 19 2005, 12:59
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That are not multiples of 128, that's just 2^n wink.gif.

I think the motivation for choice of bit rate and encoding mode is a bit conflicting with some of the aims the test.

The primary choice for the 48 kbps bit rate seems to have been to establish if HE-AACv2 is still beneficial there over HE-AACv1 (apparently consensus is that at 32 kbps v2 is better and at 64 kbps v1?)

But on the same time it must also function as pre-selection for a multiformat test and produce streams that are streamable. Now 48 kbps seems to not be the ideal choice for streaming (too high for dial-up and too low for cable/ADSL), which causes discussion about the encoding mode (if it's not for streaming why use ABR/CBR?) and already looking forward to the multiformat test it causes discussion if Vorbis should restricted to ABR/CBR, while there seems to be (at least according to some people) no real reason for making the stream streamable...

Perhaps this test is trying to do too many things at once?


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benski
post Dec 19 2005, 17:11
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QUOTE (IgorC @ Dec 16 2005, 09:45 AM)
QUOTE (Ivan Dimkovic @ Dec 16 2005, 05:41 AM)
So, I think Winamp would suit the purpose best.
*


It should be checked. CD-DA extractor also has a AAC+2 from CT and its very good. I still didnt checked Winamp 5.12 . However imo CD-DA AAC+2 was better than aac+2 from 5.11.
*



Winamp 5.12 still has the older CT encoder.
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Ivan Dimkovic
post Dec 19 2005, 18:14
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Okay, we will use whatever has the latest CT encoder at the time of the test preparation.
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IgorC
post Dec 19 2005, 22:54
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Winamp 5.12 has a newer version than previos 5.11 .5.1 ....
Maybe there will be a new 5.13 soon? There were important improvements since then.
Maybe lets wait a little?
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Ivan Dimkovic
post Dec 20 2005, 01:16
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Test is anyway scheduled for the late January, so we have one month of time for new releases of the encoders smile.gif
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rjamorim
post Dec 20 2005, 01:34
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QUOTE (JohnV @ Dec 15 2005, 12:21 PM)
One area for 48kbps would be mobile streaming in GSM EDGE and 3G -networks.
*


Isn't EDGE limited to 384kbps? That should give listeners plenty of room to listen even to 256kbps VBR.

QUOTE (Ivan Dimkovic @ Dec 16 2005, 09:28 AM)
So, we will compare best CBR encoder from the AAC test with the VBR encoder - which is quite unfair if I may say.
*


I think you guys should all go with VBR. It'll make everyone happier. Besides, I have my doubts broadcasting stations will actually use test results in their systems. I'm believe noone used mine, at least. All in all, results will only be an interesting curiosity for forum members and other audio geeks.

QUOTE (Ivan Dimkovic @ Dec 16 2005, 11:41 AM)
I think Winamp was the only software actually being able to use CT's HE-AAC v2 implementation at 48 kbps?
*


Sorenson Squeeze


About the 48kbps being streamable thing: You guys seem to forget that very few computers are on noiseless enough dial-up lines to get more than 6kBps constantly. When a streaming station goes about choosing a bitrate to broadcast their content, they must focus on the lowest common denominator and not what some lucky users that live close to the carrier can get.

On bad days here in Brazil, I couldn't even get 24kbps.

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JohnV
post Dec 20 2005, 14:16
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QUOTE (rjamorim @ Dec 20 2005, 03:34 AM)
Isn't EDGE limited to 384kbps? That should give listeners plenty of room to listen even to 256kbps VBR.

The max supported EDGE speed in the latest phone models seems to be 236.8kbps, 3G UMTS is higher about 384kbps, but there's other things you have to take into account.
1. The real life speed is often much less and varies a lot depending on the current network coverage etc.
2. In many cases you have only limited size of total bandwidth you can use per month, for example 200 or 500MB which is reasonably priced. After this the price per MB will go very high. Of course prices will go down in the future, but this is still an issue in many cases.
3. In other than in the home network roaming prices for data can be incredibly high.

etc.

That's why I think it makes much more sense to stream on average 48kbps (or lower) than a lot higher bitrate music even in high speed mobile networks.

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rjamorim
post Dec 21 2005, 00:32
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QUOTE (JohnV @ Dec 20 2005, 11:16 AM)
That's why I think it makes much more sense to stream on average 48kbps (or lower) than a lot higher bitrate music even in high speed mobile networks.
*


Ah, OK. As I understood it, EDGE would be another reason to use CBR instead of VBR.

But I see it's now obvious that even EDGE would benefit from VBR.


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digitalradiotech
post Dec 21 2005, 12:48
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A good reason to use CBR is that the new mobile broadcasting systems like DVB-H, DRM/DRM+, DMB, DAB version 2 etc, will all use CBR HE AAC.
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Ivan Dimkovic
post Dec 21 2005, 12:55
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Basically it all goes down to three use models:

1 - Narrowband Streaming over fixed-datarate networks (Digital AM/DRM, DVB-H, ISDN, modem V.90/V.92, etc...)

2 - Narrowband Streaming over variable datarate networks (Internet TCP/IP over higher bitrate DSLs / WLANs, EDGE/3G etc..)

2 - Offline content encoding (e.g. home movie collections, music that will be stored on the mobile playback device, etc...)

For 1, there is no other choice than CBR with strict bit-buffer requirements, otherwise severe bufer overlows/underflows could occur during the playback if the bitrate peak overflows capability of the transmission network. Service quality of these netorks is fixed.

For 2 it is possible to use bit-rate managed VBR, or ABR with bit buffer known a priori - it might require longer pre-buffering (i.e. if we use ABR bit buffer of, say, 64 kilobits - it would require 2-3 seconds of pre-buffer over modem) - but the quality impact might be considerable - note that service quality on such networks might vary so even strict CBR requirements might not be met if the service quality drops considerably.

For 3, it is usually desirable to use VBR, even 2-pass VBR encoding, or ABR with relaxed bit-buffer requirements - as content is usually decoded from the device possesing interface to the medium where compressed audio is stored with datarate capability way above the maximum AAC frame size.

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JohnV
post Dec 21 2005, 20:32
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One issue is also that in principle we should test as many samples as possible.
It depends quite a lot on the sample set which AAC-HE mode (V1 or V2 parametric stereo) will win.

Attached couple of samples of CT V1 and V2 where V2-PS is either clearly better or worse than CT V1 in my opinion. (Sorry no new Nero encoder samples yet biggrin.gif )
Attached File(s)
Attached File  PS_quality.zip ( 2.29MB ) Number of downloads: 322
 


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IgorC
post Dec 22 2005, 14:51
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QUOTE (JohnV @ Dec 21 2005, 11:32 AM)
One issue is also that in principle we should test as many samples as possible.
It depends quite a lot on the sample set which AAC-HE mode (V1 or V2 parametric stereo) will win.

Attached couple of samples of CT V1 and V2 where V2-PS is either clearly better or worse than CT V1 in my opinion. (Sorry no new Nero encoder samples yet biggrin.gif )
*


For your ears PS was better than simple SBR on 41_30 sample. For me it's killer sample for both. Both have different distortion. I hear on SBR something like hessing and on PS seems like some guitar drive effect.

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guruboolez
post Dec 22 2005, 14:59
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QUOTE (Ivan Dimkovic @ Dec 16 2005, 12:28 PM)
One thing which worries me here - if the part of the this test's purpose would be to decide the best competitor for the 48 kbps multiformat test - then we also have a problem.

Vorbis will be tested in its quality-controlled mode, right?
*


At last...
http://www.hydrogenaudio.org/forums/index....ndpost&p=350185

BTW, VBR should be used in the second test (the multiformat one): Vorbis...

wink.gif

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Ivan Dimkovic
post Dec 22 2005, 15:01
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Well I know for sure that Nero could supply a variable rate codec - we can do some internal tests to find out what is best.
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Ivan Dimkovic
post Dec 22 2005, 16:59
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Actually a smart idea will be to do a small pre-test, where we will determine which Nero coding mode would be the best - I could organize it in the early January.
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