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View Full Version : AAC playback background noise. Slimserver6/FreeBSD



icestorm
2005-04-24, 11:39
All,

I've just received the squeezebox2. Great little device! I've bought a sonic T-amp amplifier for it and it sounds great!

However...When I try to play AAC music from my FreeBSD server, (which is most of my music collection), I can hear a sound like a constant wind in the background, which becomes intolerable when I increase the volume. Please note that I can hear the song fine! This problem does not happen with mp3 encoded music or radio.

I am currently using SlimServer 6.0.1 and the following convert.conf entry:

mov flc * *
[faad] -w -f 2 $FILE$ | [flac] -cs --totally-silent --compression-level
-0 --endian big --sign signed --channels 2 --bps 16 --sample-rate 44100 -

It happens also in various other config such as faad+endianess swapper tool found on the web in both wav and pcm format.

faad version 2.0_5,1 according to FreeBSD pkg_info tool.

Anybody with a similar experience?

icestorm
2005-04-26, 12:54
All,

I've just received the squeezebox2. Great little device! I've bought a sonic T-amp amplifier for it and it sounds great!

However...When I try to play AAC music from my FreeBSD server, (which is most of my music collection), I can hear a sound like a constant wind in the background, which becomes intolerable when I increase the volume. Please note that I can hear the song fine! This problem does not happen with mp3 encoded music or radio.

I am currently using SlimServer 6.0.1 and the following convert.conf entry:

mov flc * *
[faad] -w -f 2 $FILE$ | [flac] -cs --totally-silent --compression-level
-0 --endian big --sign signed --channels 2 --bps 16 --sample-rate 44100 -

It happens also in various other config such as faad+endianess swapper tool found on the web in both wav and pcm format.

faad version 2.0_5,1 according to FreeBSD pkg_info tool.

Anybody with a similar experience?

ping? Anyone?

kevin
2005-04-26, 14:03
ping? Anyone?

you could try ruling out the flac conversion as an issue by creating a 'mov wav * *' or 'mov aif * *' rule depending on what the byte order is coming out of faad...

it's possibly a byte swap issue, though... usually when that happens you can still hear a semblance of the original audio, but there's just tons of distortion added.

icestorm
2005-04-30, 03:46
you could try ruling out the flac conversion as an issue by creating a 'mov wav * *' or 'mov aif * *' rule depending on what the byte order is coming out of faad...

it's possibly a byte swap issue, though... usually when that happens you can still hear a semblance of the original audio, but there's just tons of distortion added.

'mov aif' works but I can still hear the wind blowing. Please note that the songs appears to play perfectly well. The wind blowing is just extremely annoying. I cannot be the only one experiencing this problem?

Jim
2005-04-30, 09:09
The answer my friend is blowing in the wind,
The answer is blowing in the wind

(Sorry :P )

icestorm
2005-04-30, 10:54
The answer my friend is blowing in the wind,
The answer is blowing in the wind

(Sorry :P )

Unfortunately Bob was unable to assist. Does this mean I have to re-encode all my music collection to a lesser format?

kdf
2005-04-30, 12:39
Quoting icestorm <icestorm.1oashb (AT) no-mx (DOT) forums.slimdevices.com>:

>
> kevin Wrote:
> > you could try ruling out the flac conversion as an issue by creating a
> > 'mov wav * *' or 'mov aif * *' rule depending on what the byte order is
> > coming out of faad...
> >
> > it's possibly a byte swap issue, though... usually when that happens
> > you can still hear a semblance of the original audio, but there's just
> > tons of distortion added.
>
> 'mov aif' works but I can still hear the wind blowing. Please note that
> the songs appears to play perfectly well. The wind blowing is just
> extremely annoying. I cannot be the only one experiencing this problem?
>
what is the volume on your squeezebox? you will habe better signal to noise if
you run it at around 39 and adjust your amp accodingly, versus turning your amp
up to compensate for squeezebox volume of 4 or 5.

-kdf

Jim
2005-04-30, 13:00
Unfortunately Bob was unable to assist. Does this mean I have to re-encode all my music collection to a lesser format?

Yes good idea.

Instead of encoding to a lossy format such as AAC, why not encode to a lesser format such as FLAC :rolleyes

icestorm
2005-04-30, 15:19
Quoting icestorm <icestorm.1oashb (AT) no-mx (DOT) forums.slimdevices.com>:
[color=blue]

what is the volume on your squeezebox? you will habe better signal to noise if
you run it at around 39 and adjust your amp accodingly, versus turning your amp
up to compensate for squeezebox volume of 4 or 5.

-kdf


This is not a volume issue as I do not have this problem with mp3. So I guess it is a decoding issue.



Instead of encoding to a lossy format such as AAC, why not encode to a lesser format such as FLAC :rolleyes

I should have mentioned that I have an ipod and I do not feel like maintening a FLAC and AAC/MP3 collection.

Phil Karn
2005-05-07, 15:52
icestorm wrote:

> However...When I try to play AAC music from my FreeBSD server, (which
> is most of my music collection), I can hear a sound like a constant
> wind in the background, which becomes intolerable when I increase the
> volume. Please note that I can hear the song fine! This problem does
> not happen with mp3 encoded music or radio.

I seem to be having a somewhat similar problem.

I just set up AAC decoding on slimserver 6.0.2 on Linux. It works fine
with my original Squeezeboxes, but when playing on a Squeezebox2, the
audio breaks up into loud noise about a second into each AAC song.

I just isolated the problem. It only occurs when two conversions are
done in tandem, e.g., AAC->PCM->FLAC or AAC->PCM->MP3. This is why the
problem only appeared on the Squeezebox2, because the transcoding from
AAC to FLAC is done in two steps. The original Squeezebox doesn't
support FLAC, so faad converts directly to WAV.

To verify this theory, I set bit rate limiting on one of my original
Squeezeboxes to force transcoding to MP3. Sure enough, the same problem
appears.

I don't yet have a clue as to *why* this is happening. But it does,
every single time. It seems almost as if a byte of raw PCM is somehow
being dropped in the pipe between the two coders, causing a
mis-synchronization that sounds like loud noise. Whether that's actually
happening, I don't know yet.

--Phil

MathGeek
2005-05-29, 23:59
Hi Phil--

Just noticed that I have the same issue as you -- after ripping most of my collection to AAC. Did you ever find a fix?

-A