Nero recode 5.1 AAC constant lfe tone

[martok604]

Moved from mpeg-4 forum.

Hello all,

When encoding movies with Nero recode, I am getting a constant bass rumble in the lfe channel when the stream is converted back to AC3 and passed to an AV receiver and am wondering if anyone else has experienced this. The problem is reproducable on any movie with a 5.1 stream. I am using the cinema AVC profile encoding to he-aac 5.1 at 192kbit/sec using 2 pass, and 8x8 transform, not that that should matter. Taking the generated mp4 file and converting the audio to ac3, passing that out the spdif to an AV receiver results in a low and constant bass tone through my sub channel.

I have tried several ac3 encoding methods including aften and nero wave editor with the same results so am thinking something is going wrong in the encode process. Any ideas?

Tia,
Shane

[martok604]

Hello,

Looks like this might be a bug in nero recode so will have to take it up with
Nero but I've put some test files up to illustrate the problem. They are
located here:
http://www.cm.nu/~shane/nd/

test.mp4 is a 60 second clip from Lion King 2 (arbitrary choice) with 5.1
he-aac. If played back using a 5.1 system, you should get a low tone on the
sub. I then brought test.mp4 into nero wave editor to make sure it wasn't
my AAC decoder's fault and saved two files, test.ac3 and test.wav. The
ac3's channels are messed up due to AAC having a different channel order
than AC3 so the bass tone is on the left reer channel, the wav decode shows
it also, also on left reer.

I'm using latest recode from nero 7.7.5.2 and would be curious if this is a
problem with older recode versions as a downgrade might be in order.

[JohnV]

Try with Recode in Nero 7.8.5.0. I hear from your examples what you mean, but can't reproduce that.

[shon3i]

Moved from mpeg-4 forum.

Hello all,

When encoding movies with Nero recode, I am getting a constant bass rumble in the lfe channel when the stream is converted back to AC3 and passed to an AV receiver and am wondering if anyone else has experienced this. The problem is reproducable on any movie with a 5.1 stream. I am using the cinema AVC profile encoding to he-aac 5.1 at 192kbit/sec using 2 pass, and 8x8 transform, not that that should matter. Taking the generated mp4 file and converting the audio to ac3, passing that out the spdif to an AV receiver results in a low and constant bass tone through my sub channel.

I have tried several ac3 encoding methods including aften and nero wave editor with the same results so am thinking something is going wrong in the encode process. Any ideas?

Tia,
Shane
I've just checked and it is true. But that isn't nero recode bug, and is not bug at all. The problem is in Nero AAC encoder (isn't bug, just nero policy of 5.1 encoding ;)), which use lowpass for LFE channel to save bits for Front and Center channels. That make very quiet LFE channel. To solove this problem in future, better to use CT AAC encoder instead.

If you want transcode AAC->AC3 with correct channel order, use BeHappy.

[tebasuna51]

The problem is in Nero AAC encoder (isn't bug, just nero policy of 5.1 encoding ;)), which use lowpass for LFE channel to save bits for Front and Center channels.
But lowpass LFE is a common technic also for ac3 and don't justify the fix bass rumble present in aac sample. We need the original source before the aac to check if is NeroAacEnc the culprit.
If you want transcode AAC->AC3 with correct channel order, use BeHappy.
With BeHappy, for decode multichannel aac, we need use DirectShowSource sometimes problematic. Foobar2000 like decoder with Aften encoder can be used also.

[martok604]

Hi,

I did try totally uninstalling Nero and installing the 7.8.5.0 from the nero
website with the same bass hum coming out of Recode. Further, I tried it on
my Laptop with the same results. it isn't a low lfe signal as a poster
indicated but rather a constant loudish buzzing sound. It comes out
regardless of the source DVD used as long as it has a 5.1 ac3 audio track.
However, if a source stream would be helpful, I have posted the ac3 here.
http://s182231586.onlinehome.us/nd/01-source.ac3

One strangeness though, if source.ac3 is pulled into nero wave editor and
saved as nd audio, the LFE is fine, no hum. Is limited to recode it would
seem.

[shon3i]

But lowpass LFE is a common technic also for ac3 and don't justify the fix bass rumble present in aac sample. We need the original source before the aac to check if is NeroAacEnc the culprit.
Agree about lowpass,but nero use really hard lowpassing on LFE channel, comparing to CT AAC is too much, and after lowpassing decrase volume.

If you use any 5.1 AC3, DTS or other multichannel sound, and encode with both CT and Nero, on any bitrate, you will see in program such Adobe Audition in Spectral Analyzer, what nero does on LFE channel, aslo in Audition you can check averge RMS power, and will see that nero make LFE very silent, aslo you can do an ABX test, which make to clear things better.

I can attach images if you want?

[JohnV]

I've just checked and it is true. But that isn't nero recode bug, and is not bug at all. The problem is in Nero AAC encoder (isn't bug, just nero policy of 5.1 encoding ;)), which use lowpass for LFE channel to save bits for Front and Center channels. That make very quiet LFE channel. To solove this problem in future, better to use CT AAC encoder instead.

If you want transcode AAC->AC3 with correct channel order, use BeHappy.Not any Nero policy and martok604 talks about totally different issue.

[JohnV]

Hi,

I did try totally uninstalling Nero and installing the 7.8.5.0 from the nero
website with the same bass hum coming out of Recode. Further, I tried it on
my Laptop with the same results. it isn't a low lfe signal as a poster
indicated but rather a constant loudish buzzing sound. It comes out
regardless of the source DVD used as long as it has a 5.1 ac3 audio track.
However, if a source stream would be helpful, I have posted the ac3 here.
http://s182231586.onlinehome.us/nd/01-source.ac3

One strangeness though, if source.ac3 is pulled into nero wave editor and
saved as nd audio, the LFE is fine, no hum. Is limited to recode it would
seem.I still can't replicate the problem with your ac3-source (I don't get the same problematic buzz as in your examples). I'm starting to think it maybe some filter conflict. If you use some DS ac3 filter (ffdshow/ac3filter), try disabling it first and then try encoding with Recode.

[tebasuna51]

Like JohnV, I can't reproduce the problem encoding your 01-source.ac3 with NeroAacEnc (Feb 12 2007).

Tried also with old nero dll's method and the fix bass rumble don't appear.

BTW, with my old ears, I can't difference Nero and CT encoders.

Seems a problem with your Nero Recode configuration.

[martok604]

Hello,

Thanks to all those who have replied. I'm still trying to get a handle on this one. One thing that might help narrow the problem though is the low hum seems to only occur when reading DVD content directly with recode. IE. encode dvds and video to nero digital, clicking import files and selecting a title from a DVD folder or mounted drive. If I extract the mpeg stream for the main movie from the DVD structure and import that mpeg into recode, it encodes the audio correctly. I don't get chapter information that way but it does seem to work.

I've tried both DVD decrypter and daemontools for the rips with the same results.

[JohnV]

I'm still trying to get a handle on this one. One thing that might help narrow the problem though is the low hum seems to only occur when reading DVD content directly with recode. IE. encode dvds and video to nero digital, clicking import files and selecting a title from a DVD folder or mounted drive. If I extract the mpeg stream for the main movie from the DVD structure and import that mpeg into recode, it encodes the audio correctly. I don't get chapter information that way but it does seem to work.Yes I got it. Indeed it's ok with individual files, but not when encoding a DVD title to 5.1ch. Definitely a pretty serious audio bug.. prio1.
Thanks for reporting.

[Greif]

any update on this bug? is there an eta on the release of next version which fixes this?

[martok604]

Hello,

Just got the Nero 7.9.6 update via nero product setup.
Unfortunately, this issue is still present for me in this
version. Just fyi.
Shane

[Greif]

I was also hoping the latest release would provide ac3 + Cinema/HDTV AVC in the nero digital container.

I guess we have to wait a while for that too.

[wunschkind]

having same problems here with the newest nero version (7.9.6.0)

i hope this will change in future. thank you very much for the support.


wunschkind

p.s. the sound seems to be ok with nero 7.5.7.0

[martok604]

Hi,

Is the 7.5 download available anywhere? Just looking at
the nero site and only see the 7.9 version. Lose high
profile with 7.5 I believe but that's a small price to pay.

[wunschkind]

hi,

http://www.filehippo.com/download_nero_7_premium/?1708

wunschkind

[westgroveg]

Disappointing a retail program could have such a major bug...

I should have used freeware programs instead, hahaha

[CzechMate]

Is there any update on this issue? A patch or anything. It pretty much makes recode unusable.

[roket scyntist]

Any news on this? I have halted most of my encoding work until this is fixed. All my encodes from DVD have this problem.

[CzechMate]

Any news on this? I have halted most of my encoding work until this is fixed. All my encodes from DVD have this problem.

He replied to another thread (http://forum.doom9.org/showthread.php?p=1014591#post1014591)on Friday with this:

Juha, is there any word on fixing the audio problem (the low buzz)?

Some other tasks have got higher priority atm, but it's not forgotten. I know it's very irritating, I just read the latest comments on that specific thread, so I'll do some pushing to hopefully get it priorisized.

[roket scyntist]

He replied to another thread (http://forum.doom9.org/showthread.php?p=1014591#post1014591)on Friday with this:



Some other tasks have got higher priority atm, but it's not forgotten. I know it's very irritating, I just read the latest comments on that specific thread, so I'll do some pushing to hopefully get it priorisized.

Thanks.
Glad to know they are still looking at it.

[unrealism]

I get this as well... I have a MediaCenter setup with FFDSHOW+CoreAAC decoding to 5.1. I am using a Auzentech XPlosion soundcard and a Sony 5.1 Surround system. I cant get that LFE channel to stop buzzin. The only two work arrounds so far is using the surround sound placement utility with the soundcard... I move the LFE back which decreases the volume of that speaker, however I am probly losing some quality. :( Or use MPlayer and use the EQ to lower it... Is there a fix for this?

[roket scyntist]

Doesn't look like it. I'm using staxrip for now (actually getting into it, kinda cool :-). I like the compressibility check (despite what people say).

Another way to do this just for now, is to encode with recode (select no audio), do a manual encode to aac using the nero command line encoder, then mux the video and audio using mp4box. Bit of a mission, but it works.

[unrealism]

I dont think that would be to ideal, considering I have about 320+ movies already done, not to mention to go back and redo all that? No thanks! haha There has to be a way around this.

[JohnV]

The LFE hum bug has been fixed. I'm waiting for info when it's gonna be available, or if I can provide the filter beforehand.

[wunschkind]

hi,

this is really great. thank you. waiting for the update

[unrealism]

AWESOME! Does that mean I have to recode all my movies though? :confused:

[JohnV]

AWESOME! Does that mean I have to recode all my movies though? :confused:
Well for those movies which have the problem, you could encode just the audio of the DVDs again and mux it. At least that saves the video encoding time, so it would be much faster than encoding the whole thing again.

[roket scyntist]

Thanks JohnV for the info. Looking forward to it.

[unrealism]

Will there be a tool for this? How do I go about doing that? I understand what your saying, I just dont know how to do it with Nero. :stupid:

[unrealism]

:bump:

[JohnV]

Will there be a tool for this? How do I go about doing that? I understand what your saying, I just dont know how to do it with Nero. :stupid:
I could take a look how to do it, but the fix is not out yet. I'd think the easiest is to encode the DVD with minimum video settings and resize to 16x16, then use YAMB or graphedit for splitting and muxing.

The fix is not going to make to the next web update, it was done too late. Didn't get the word yet if the fix can be pre-released.

[SuperGoggles]

Hi All,

I've been suffering this problem for months.

I thought it was a hosed install of XP until i completely upgraded to XP pro and had the same problem on a different hardware config. I've recently upgraded to Vista and the problem is still repeatable there. So, I tried to work out a way to make it repeatable for Nero tech support to analyse as it's deffo a bug in Nero.

Nero tech support are obviously unaware that this is a known bug and that there is a fix in motion if not out yet, and their constant advice - despite how I explained that it's repeatable on all my various test machines - was to do a clean install - something i said I had already tried, many, many times!

In my case I noticed it's not a problem with the encoding process, but a bug in the decode process, but ONLY when the Cinema profile is selected. By default audio preview is set to stereo and not stereo-downmix so you don't normally notice it prior to encoding any surround sound mixes.

Try the following:-
# Load recode.
# Import a surround-sound DVD (5.1) into the recode video list.
# Set the encode profile to Cinema, select the 5.1 audio channel mix.
# In the video preview pane set the preview audio track to the multichannel (5.1) track.
# Set the audio preview mode to "Stereo downmix" to hear the problem on a stereo soundcard.
# Play preview video.
# Notice the buzz/hum.
# Now stop playback and change the encode profile to High Def or Standard.
# Restart the preview and the hum should be gone.

My temporary solution based on this is to NOT encode with Cinema profile until the bug is fixed. Instead use either High Def or Standard.

Let me know how you get on. If this is also the problem you are seeing (hearing), is there a specific reason you need to you the Cinema profile for your encodes?

Cheers,

[JohnV]

Hi All,

I've been suffering this problem for months.

I thought it was a hosed install of XP until i completely upgraded to XP pro and had the same problem on a different hardware config. I've recently upgraded to Vista and the problem is still repeatable there. So, I tried to work out a way to make it repeatable for Nero tech support to analyse as it's deffo a bug in Nero.

Nero tech support are obviously unaware that this is a known bug and that there is a fix in motion if not out yet, and their constant advice - despite how I explained that it's repeatable on all my various test machines - was to do a clean install - something i said I had already tried, many, many times!

In my case I noticed it's not a problem with the encoding process, but a bug in the decode process, but ONLY when the Cinema profile is selected. By default audio preview is set to stereo and not stereo-downmix so you don't normally notice it prior to encoding any surround sound mixes.

Try the following:-
# Load recode.
# Import a surround-sound DVD (5.1) into the recode video list.
# Set the encode profile to Cinema, select the 5.1 audio channel mix.
# In the video preview pane set the preview audio track to the multichannel (5.1) track.
# Set the audio preview mode to "Stereo downmix" to hear the problem on a stereo soundcard.
# Play preview video.
# Notice the buzz/hum.
# Now stop playback and change the encode profile to High Def or Standard.
# Restart the preview and the hum should be gone.

My temporary solution based on this is to NOT encode with Cinema profile until the bug is fixed. Instead use either High Def or Standard.

Let me know how you get on. If this is also the problem you are seeing (hearing), is there a specific reason you need to you the Cinema profile for your encodes?

Cheers,
Unfortunately you are incorrect. Try encoding just a chapter of a DVD with 5.1 the problem is there also with Standard and HighDef/HDTV...
I try to get permission to get the fix out, but if it's not possible, you have to wait at least a month cause the shortly appearing update doesn't according to my info include the fix yet.. :( But the fix is done already.

[SuperGoggles]

Unfortunately you are incorrect. Try encoding just a chapter of a DVD with 5.1 the problem is there also with Standard and HighDef/HDTV...
I try to get permission to get the fix out, but if it's not possible, you have to wait at least a month cause the shortly appearing update doesn't according to my info include the fix yet.. :( But the fix is done already.

Ah, i guess i've been lucky in only noticing it for full video encodes/playbacks. At least i've found my workaround for the moment as I generally don't encode just chapters and I don't need to play these videos away from the Nero software (such as a Nero-compatible standalone DVD player), so the high def profile is fine for my use as I generally encode to 3MBits/s which creates fairly large/high quality files. For going away, 2MBits/s in stereo under Cinema profile works fine for general laptop playback.

Deffo looking forward to the fix whenever available! My patience is generally very good for things like these. Thanks for keeping us posted!

Cheers,

[Greif]

Yeah, if the fix is not included in the upcoming update then a filter fix would be greatly appreciated. I've been waiting for months for this issue to be addressed.

[unrealism]

So can I still go ahead and keep recoding my files? Or should I stop and wait for the fix? Is it in the encode or decode causing this? All I can say is I love Nero Digital however the LFE is causing me nothing but a headache! The bass is overwhelming. :(

[martok604]

unrealism,

If you're doing DVD encoding, I would suggest not using
Recode until this is addressed. My tests conclude the
problem is in the encode and not the decode. That is, you
can use any H.264 decoder to get this result provided
you do a pure 5.1 decode and though you could remux things
later, that can be a pain and would mean an audio reencode
anyway. Not to mention the potential sync issues doing
this.

[JohnV]

martok604 is correct. I would suggest stalling encodings with 5.1ch audio until the fix is released. Unfortunately still no word when it will be out.

[SuperGoggles]

unrealism,

... My tests conclude the
problem is in the encode and not the decode...

My experience suggests it's in the decoding of the source prior to encode, and not strictly the encoding itself (although for me the choice of profile affects the presence of the hum). So it may be worth looking into the steps I provided above to see of you get the same situation. If so, and if you use high bitrates anyway, you could try switching to High Def - if this works and is a suitable alternative for you.

As JohnV said, if you are only encoding certain chapters, and not the whole movie, then it would be best to wait for the official fix release. Otherwise, the next best option would be to extract the section(s) of video you want to encode using another video program (haven't investigated with Nero, but I'm pretty certain I can do this in Vegas - maintaining the surround sound). It is then possible to "create" a soft DVD movie folder (with DVD Architect) or a DVD image (with Nero) of this video and then load this into Recode to convert to High Def.
I know it's a bit long-winded, but if desperation prevails, either of these could be worth looking into!

Personally, as I've found my fix for the time being, I'm happy to use the High Def encode option, as I tend to use high bitrates for my videos anyway - 3Mb+.

YMMV

Cheers,

[JohnV]

To be precise, the problem is/was in the ac3 decoding chain when processing a DVD 5.1ch. The actual AAC encoding in Recode is working correctly, but it gets the messed up DVD AC3 5.1 LFE input, so the audio encode ends up like that too.

[unrealism]

JohnV,

So what your saying is this...

DVD RIP--->Nero Recode--->Analog Speakers Works fine!

From PC to 5.1 reciever digitally--->Loud LFE Tone!


But all together Nero is recoding the 5.1 correctly, but when sent to a 5.1 reciever it spits out a loud LFE tone? I wonder this, because I dont hear it on normal PC speakers!

:confused:

[JohnV]

No. The buggy lfe hum is there in the stream. I just meant the AAC encoder faithfully encodes the faulty AC3 decoding of DVD audio.

Speakers/receivers has nothing to do with the actual problem. Reason why you don't hear it with PC speakers is somewhere else.

[martok604]

JohnV,

Do you know whether the bug affects AC3 2ch or 2.1 ch or is
it limited to 5.1ch input. I don't hear it with 2ch but
that's not to say it isn't there. My prologic decoding
might be filtering it out and if it's in the bitstream
at all, those bits could be used for encoding something
more useful.
Just wondering if it's safe to go ahead and use Recode for
stereo or prologic input.

Shane

[unrealism]

JohnV,

Do you know whether the bug affects AC3 2ch or 2.1 ch or is
it limited to 5.1ch input. I don't hear it with 2ch but
that's not to say it isn't there. My prologic decoding
might be filtering it out and if it's in the bitstream
at all, those bits could be used for encoding something
more useful.
Just wondering if it's safe to go ahead and use Recode for
stereo or prologic input.

Shane

Or is it safe to encode period to 5.1? I gots to do more encoding. :)

[JohnV]

JohnV,

Do you know whether the bug affects AC3 2ch or 2.1 ch or is
it limited to 5.1ch input. I don't hear it with 2ch but
that's not to say it isn't there. My prologic decoding
might be filtering it out and if it's in the bitstream
at all, those bits could be used for encoding something
more useful.
Just wondering if it's safe to go ahead and use Recode for
stereo or prologic input.

Shane

Bug is not there with 2ch. Also 5.1->2ch downmix in Recode is ok. You definitely would hear the bug very well with 2 speakers when 5.1->2ch downmixed with lfe during playback.

Also,if you take an individual .VOB file as input instead of the whole DVD (main movie encode), then there's no lfe bug, because the decoding chain in Recode is different for individual files and the bug is in the DVD main movie audio decoding chain with 5.1 ac3 input.

[unrealism]

So still I guess I should wait on encoding any further untill a "fix" is available? :stupid:

[unrealism]

Oh agony, my drive is full. DivX video sux, but the AC3 is awesome... Nero stole my heart and broke it with a loud LFE tone! lol please fix asap! :)