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Rhythmic hiccup when playing music from G-Safe raid via MegaSeg

I'm in the process of bulding an internet radio station.

The hardware: PowerPC G5 dual 2 GHz, 2.5 GB RAM, OS-X 10.5.8. Partnered with a 3 TB G-SAFE raid.

The software: iTunes 10.4.1, MegaSeg 5.7.3

MegaSeg is a piece of software designed for internet radio and DJ purposes. It integrates with the iTunes library.

I started out using a LaCie external drive while I loaded music. That drive performed flawlessly. I could have MegaSeg playing music while iTunes imported CDs. I even could have MegaSeg, iTunes, and the QuickTime Player all playing songs while iTunes was importing a CD, and never had a hiccup.

But I wanted a truly large storage system, and the security of a RAID. So I bought the 3 TB G-SAFE.

The problem is that every 2 minutes and 3 seconds, music from MegaSeg pauses. The length of the pauses varies from a mere hiccup to a noticeable pause, but it happens every 2:03.

The pause does not happen when I use iTunes or QuickTime Player with the G-SAFE. The pause does not happen when I use MegaSeg with the LaCie drive or the internal drive. Nothing I do changes the interval or duration of the hiccups. Whether I do a cold start, launching only MegaSeg, or have iTunes running, surf the internet, and upload CDs, the hiccups sconsistenyly happen every 2:03.

G-SAFE assures me that the drive cannot be the culprit, since it functions as expected with most utilities, and the AJA performance tests are good.

MegaSeg assures me that the problem can't be with their software, since it functions properly with other drives.

So, what is the deal? What is the system doing every 2:03? I've stared at the Activity Monitor for hours on end, and there's no striking correlation between any system activity and the pauses. There is a weak correlation with a minor write access, but it's not consistent, and the system does not hiccup during much more pronounced write activities.

What I've tried:

-reformatting the G-SAFE

-repairing permissions, zapping PRAM

-disabling or enabling about every option MegaSeg has to offer

-force quitting the MIDI process (suggested by the MegaSeg developer)

-cold starting and launching only MegaSeg

-runing AJA system performance tests on the G-SAFE

-crossing my fingers

Please help!

Tom G

Posted on Nov 25, 2011 6:52 PM

35 replies

BDAqua

Level 10

239,363 points

Nov 28, 2011 3:56 PM in response to HawaiianHippie

Click on the system memory tab, any Page Outs when it happens a few times?

Nov 28, 2011 4:54 PM in response to BDAqua

Nope, no Page Outs.

BDAqua

Level 10

239,363 points

Nov 28, 2011 5:28 PM in response to HawaiianHippie

Whew!?

I would've thought the Console log would've shown this, but are you getting any increasing logs in...

/Users/YourUserName/Library/Logs/

/Library/Logs/

private/var/log/

Some Apps have their own place like...

/Applications/DigiPosts v2.0/logs/

Nov 28, 2011 5:55 PM in response to BDAqua

megaSeg makes a daily log, but it's just a playlist, used for reporting to music magazines, record labels, and rights organizations. I'm not seeing the private/var/log/ directory anywhere, but the others you listed don't contain much.

BDAqua

Level 10

239,363 points

Nov 28, 2011 6:15 PM in response to HawaiianHippie

private is normally hidden but the biggest repository. It's the one you see in Console if you select all logs.

Show Hidden Files 1.0...

http://www.macupdate.com/app/mac/29096/show-hidden-files

Hidden Way is a toggle for hidden files view in Finder...

http://www.macupdate.com/app/mac/25716/hidden-way

Show hidden files in OSX Finder

Open the Terminal and type or copy/paste:

defaults write com.apple.finder AppleShowAllFiles -bool true

Reverting to the default of NOT showing hidden files:

defaults write com.apple.finder AppleShowAllFiles -bool false

*Restart or Force Quit Finder required to take effect.*

http://www.apple.com/downloads/dashboard/developer/hiddenfiles.html

http://www.burobjorn.nl/blog/?p=96

Finder Force Quit, or restart required to take effect.

japamac

Level 7

24,400 points

Nov 29, 2011 3:14 AM in response to HawaiianHippie

The pauses don't correspond with any jump in processor load or network activity. There is some correlation with a write activity, but that particular activity is a smaller spike than other activities which do not correspond with the hiccup at all.

I didn't say, but the one thing that makes me feel the issue is tied to the G-Safe controller is the fact that the drive is a RAID 1; there is a write to the mirror for every write to the primary- logs included.

Is there a G-Safe entry (or IO/Controller/PCI related kext) in the logs around the time of the pause/delay?

Nov 29, 2011 3:10 PM in response to japamac

No, the logs and Console remain stubbornly empty while this happens.

Nov 29, 2011 3:13 PM in response to HawaiianHippie

BREAKING NEWS!

It's related to file types.

I was working on an email to the developer, and morbidly watching my stopwatch, and it missed a hiccup. Then it missed another. Then a 3rd. Then a new song started, and the behavior resumed.

Curious, I looked at the last song, and discovered it to be a .mp3. This differs from the majority of the songs in my iTunes library, which are .m4a. I loaded up a playlist of .mp3 tunes, and it played flawlessly.

So, it's an even more specific combination than I originally posted: MegaSeg + G-SAFE + .m4a

BDAqua

Level 10

239,363 points

Nov 29, 2011 4:39 PM in response to HawaiianHippie

Wow, great work! 😀

Are those .m4a files Advanced Audio Coding (AAC) codec or the Apple Lossless Audio Codec (ALAC)?

Have you tried converting some to something else for a test?

It now sounds like the G-Safe drivers & decompression method are vying for some CPU resource, maybe Altivec?

Nov 29, 2011 6:35 PM in response to BDAqua

They were imported through iTunes using the AAC encoder set to "iTunes Plus."

Although I should mention that I only recently enabled error correction, maybe the most recent 3,000 songs or so.

I'll try doing a few conversions tomorrow and see what results I get. I must say, though, the thought of having to convert the entire library (over 10,000 songs) seems... unweildy.

[EDIT]

I searched for Altivec in the list of processes. I don't see it there.

BDAqua

Level 10

239,363 points

Nov 29, 2011 6:42 PM in response to HawaiianHippie

I don't know how much you trust my psychic ability, but there is Velocity Engine... which is Altivec! 😉

I wonder if you could convert a whole folder with this method, ( a duplicated folder of course...

http://osxdaily.com/2010/05/01/convert-songs-to-mp3-aac-m4a-or-other-formats-in- itunes-9-1/

Nov 30, 2011 7:05 PM in response to BDAqua

Today, I picked a nice long song (Yes "Starship Troopers" One of my all-time favorites.) I imported it into iTunes 5 times, once each as .wav, .m4a (AAC), .m4a (Apple Lossless), .aiff, and ,mp3. Then I sat and listened to each in its entirety, stopwatch in hand. The results:

.wav, .aiff, .mp3: no hiccups.

.m4a (AAC), .m4a (Apple Lossless): hiccups every 2:03

I also searched the Activity Monitor for the Velocity Engine. Couldn't find that either.

BDAqua

Level 10

239,363 points

Nov 30, 2011 7:45 PM in response to HawaiianHippie

You won't see Altivec or Velocity Engine ever show in AM.

BDAqua

Level 10

239,363 points

Nov 30, 2011 10:30 PM in response to HawaiianHippie

Didn't mean to br cryptic, but in your AAC pic above, it is using Altivec/Velocity engine, I suspect .wav, .aiff, .mp3 probably do not use it, or at least so much.

Nov 30, 2011 11:10 PM in response to BDAqua

So, how does this help me?

Moving forward, I can certainly use another encoder. But for the 10,049 songs currently encoded in .m4a, I have a problem.

iTunes would let me transcode them, that part is easy enough. What isn't easy is that MegaSeg lets you assign additional data to each music file. Additional categories, notes, cross referenced artists... the list is long. And a large percentage of those 10,049 song files have additional data attached to them. Additional data that does not move if the file gets renamed from "song.m4a" to "song.aiff". We're talking, literally, about 6 weeks of daily effort, 3-4 hours each day. I'm not willing to entertain the idea of going back through all those songs and manually re-entering the additional data.

What's the next step towards finding an actual solution?

Rhythmic hiccup when playing music from G-Safe raid via MegaSeg