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Topic: Problem sample for Nero AAC (Read 13066 times) previous topic - next topic
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Problem sample for Nero AAC

Hi,

I've uploaded a terrible problem sample for Nero.. It's from a beginning of a symphony. Nero AAC seems to have a massive problem with the background noise. It adds permanent metallic noise. The encoder chooses very low av. bitrate at 89 kbps.
I have replaygained the flac file and added the same replaygain values to the aac manually. For systems without replaygain, turn up the volume.

The files are here. The AAC file has been encoded with the latest free nero encoder @ q 0.6. I did a quick test with Lame@V2, it doesn't have such problems, encodes to >180 kbps av.

Michael

EDIT: BTW its this CD set and the noise will also be added in the beginning of Symphonies Nos. 1/1. mvmt., 1/2. mvmt., 6/1. mvmt., 6/3. mvmt.

Problem sample for Nero AAC

Reply #1
I've repeated conversion from your *.flac, using fb2k two times:
1. converting and then applying replaygain,
2. converting and using replaygain during conversion.
In the first case result was almost identical with your file, in the second case it seems that problem has disappeared.

Problem sample for Nero AAC

Reply #2
Yes, not surprising the problem has gone there, because the AAC encoder encodes different (loud) audio material then.

Problem sample for Nero AAC

Reply #3
BTW, this is a very serious problem when encoding classical music. I've seen the effect in some other some other tracks (different productions) as well.

Didn't realize it was the AAC encoder because I convert my music with fb2k+vlevel dsp for mainly listening in car. And my belief in the AAC encoder at 0.6 was high...  I always thougt it was a vlevel dsp problem.

Currently, I would never encode classical music with nero aac, the encoder is very likely to fail.

Problem sample for Nero AAC

Reply #4
Currently, I would never encode classical music with nero aac, the encoder is very likely to fail.

I'm afraid that your conclusion is absolutely wrong. At first, go to http://www.rarewares.org/aac-encoders.php and download AACGain v1.7, then apply to sibelius3_2.mp4 file and then play it in Winamp (file properties indicate that replaygain is 27.33 dB), enabling replaygain. You will be surprised! The same file in fb2k is understood as without replaygain. IMHO NERO AAC encoder is perfect.

Problem sample for Nero AAC

Reply #5
[edit] Need to do some proper testing when there's more time.

Problem sample for Nero AAC

Reply #6
Yes, I think I was wrong in my statement. But what's the cause of the effect?

1. fb2k, no replaygain applied, turned up my amplifier very much: the effect isn't almost there.
2. fb2k with apply gain: the effect is there
3. winamp, no rg: same as 1.
4. Winamp with rg: Cannot find how to let Winamp apply rg, please let me know.

This looks like some kind of decoder failure or side effects of amplifying.

Problem sample for Nero AAC

Reply #7

Currently, I would never encode classical music with nero aac, the encoder is very likely to fail.

I'm afraid that your conclusion is absolutely wrong. At first, go to http://www.rarewares.org/aac-encoders.php and download AACGain v1.7, then apply to sibelius3_2.mp4 file and then play it in Winamp (file properties indicate that replaygain is 27.33 dB), enabling replaygain. You will be surprised! The same file in fb2k is understood as without replaygain. IMHO NERO AAC encoder is perfect.


I have to disagree.  I hear the artifacts in Winamp as well.  It's not subtle at all, and I was just using a lot of volume knob.  It is a metallic sound akin to the failures of the earliest MP3 encoders.  And at q 0.60, there's even a stutter hiss at the very beginning.  Wow.  It's definitely an encoder problem.  But I wouldn't go so far as Squeller saying Nero AAC is likely to fail on classical.  It fails on very, very, very, very, very... very, very, very low background hiss.

[update]
I just reencoded this test sample using the "-he" switch at q 0.60 and the metallic hiss is gone almost completely.  SBR saves the day even at high bitrates... in this isolated case anyway. 

Just for curiosity, I also encoded this same sample with Vorbis q7 (comparable bitrate match to AAC q0.6), and it compressed it at 187kbps.  Musepack --insane (~240 target) compresses it 212kbps.  Whereas Nero AAC q0.6 compresses it at 90kbps in LC mode and 71kbps in HE mode.  I think Nero AAC's problem is not allocating enough bits to this (for all practical purposes) audibly insignificant section, which logically makes sense since if you don't jack up the volume knob to 15 (out of 10) you can't hear this anyway.  However, using SBR replicates this inaudible high frequency hiss using noise generation and "fixes" it.

Problem sample for Nero AAC

Reply #8
Very interesting, as common opinion says that HE-AAC isn't useful at moderate or high bitrate.
There has been this discussion with the special listening tests on www.soundexpert.info where high bitrate HE-AAC came out surprisingly good though in theory shouldn't.

I think such an example and behavior of an encoder demonstrates how people feel about things.
Practitioners feel 'usually things are very fine with a good encoder and the usual settings at moderate bitate - with few exceptions'. And they're right. Perfectionists say 'Well, I'd like to go a bit beyond that' and use a very high quality setting which usually is overkill, maybe CBR/ABR instead of VBR at very high bitrate, special features like HE-AAC, or whatsoever seems promising, and their way is right as well.
The most important question to everybody is 'Am I a practitioner or a perfectionist?', accept either way, and choose an encoder and setting accordingly. After all we want to be happy. That's why it's so useless when for instance a practitioner tells a perfectionist 'use setting xy, it's fine in nearly any circumstance, and if you want more: go straight lossless'. That's the practitioner's view, not very valuable to a perfectionist (only in case he hasn't heard about lossless). The other way around the same of course. Unfortunately we read many discussions here that are useless cause their background is just this. Moreover they have a tendency to be very long and emotional just because two incompatible worlds meet.
lame3995o -Q1.7 --lowpass 17

Problem sample for Nero AAC

Reply #9
But I wouldn't go so far as Squeller saying Nero AAC is likely to fail on classical.  It fails on very, very, very, very, very... very, very, very low background hiss.

Yes, I admit I was a bit "overimpressed" by the effect, because what I finally did (I was lazy) was I transcoded the track for my car and used replaygain and the vlevel dsp. So what happened was, the very silent parts with the effect have been made louder.

It's true the effect is there, but it seems "digitally amplifying" (replaygain) does make it sound much worse than analog amplifying (turning the stereos amp. volume knob to "15 (out of 10)" ).

I think Nero AAC's problem is not allocating enough bits to this (for all practical purposes) audibly insignifiant section, which logically makes sense since if you don't jack up the volume knob to 15 (out of 10) you can't hear this anyway.  However, using SBR replicates this inaudible high frequency hiss using noise generation and "fixes" it.
I agree. But IMO the encoder should be more conservative at that high quality levels.

Problem sample for Nero AAC

Reply #10
One stupid question, where are NERO AAC developers?
We are discussing and they probably sleep.
Wake up, please!

Problem sample for Nero AAC

Reply #11
.... As said here we are looking into this. The problem has been isolated.

Problem sample for Nero AAC

Reply #12
Question out of topic:
I'm looking for a little playback program for nero mp4 audio files like "aacDECdrop" (with SBR+PS support). "aacDECdrop" doesn't play it right. A Command-line utility would be enough. I want to generate music previews with foobar and "nero 1.1.34.2 -q 0.15" and offer other people a little program to play them. Most of them don't want to install anything or are using strange music player which doesn't play it right.

*edit*
On rarewares.org - FAAD 2 for Win32: "and can playback AAC/MP4 streams"
There's no option to playback a file. I've checked the "-help".