789:57:13

Saturday, 7. November 2009

I recently had several tracks stop playing in iTunes and they all had one thing in common, a duration of 789:57:13. The recommended solution for this problem is to re-rip or re-download the track. That wasn’t an option for some of these tracks because I purchased them through iTunes and the official Apple stance is that you are only allowed to download a purchased track once and I didn’t want to re-purchase the tracks. Restoring from backup also wasn’t an option for some of the tracks because they were munged in even my oldest backups.

The solution I found was faad and faac – Freeware Advanced Audio Decoder/Coder. It will decode unencrypted AAC/MP4 files and will happily ignore and correct the munged frame duration in the MP4 wrapper. I recovered a damaged track like this:

faad "09 This Devil's Workday.m4a" -o "09 This Devil's Workday.wav"

mv "09 This Devil's Workday.m4a" "09 This Devil's Workday.m4a.bad"

faac -w --artist "Modest Mouse" --title "This Devil's Workday" --album "Good News for People Who Love Bad News" --track 9 --disc 1 --year 2004 "09 This Devil's Workday.wav"

As faad was decoding the original track it showed that the MP4 wrapper’s duration was, but it corrected as it decoded it.

MP4 seems to have incorrect frame duration, using values from AAC data.
Decoding 09 This Devil's Workday.m4a took: 1.62 sec. 85.94x real-time.

When faad/faac were done I was able to re-import the track into iTunes and play it successfully.

Caveats

I lost some of the iTunes metadata from the original track, mainly the cover art. iTunes automatically added the cover art when I re-imported it, but that only works for music in the iTunes library. In those cases, faac has an option to import cover art from an external image file. You can do the same thing with iTunes as well.

If you have a lot of tracks to repair, adding the metadata manually on the command line is tedious. However, it could be automated with a simple script that captures and processes the output of faad since it displays all the track metadata as it is processing.


Cross-posted on deanfranklin.net.

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Ubuntu 9.04 (Jaunty Jackalope) Problems Fixed

Saturday, 2. May 2009

No Terminal

I put a band-aid over this problem by adding /dev/pty to /etc/fstab. After revisiting this bug report I found that the source of the problem was that I was missing a symlink in /etc/rcS.d. If you are having the same problem first check that
/etc/init.d/mountdevsubfs.sh exists and then run the following commands:

cd /etc/rcS.d/

sudo ln -s ../init.d/mountdevsubfs.sh S11mountdevsubfs.sh

However, there is no explanation for why this symlink was missing in the first place.

No RAID

This turned out to be an extremely easy problem to fix. While fixing the symlink problem above I noticed that init scripts weren't ordered correctly. The init scripts for disk mounting were happening too early, before the mdadm module and services had fully loaded. That's why my RAID volume wasn't mounting on startup but I could mount it manually after logging in. I corrected the order of the init scripts and now the RAID volume auto-mounts when booting.

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Ubuntu 9.04 (Jaunty Jackalope) Sound Problem Fixed

Friday, 24. April 2009

I found someone else reporting the same problem here. The problem turned out to be that the PCM volume in the ALSA mixer had gotten muted. I'm not sure if the upgrade to 9.04 caused that or something else did. Whatever the case, the sound is working great and there's no more crackling.

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Ubuntu 9.04 (Jaunty Jackalope) Upgrade Notes

Friday, 24. April 2009

I upgraded from Ubuntu 8.10 (Intrepid Ibix) to Ubuntu 9.04 (Jaunty Jackalope). It went fairly well but after the upgrade I found three major problems.

No Terminal

When I tried to launch GNOME Terminal from the menu I got this message:

There was an error creating the child process for this terminal

Not good. The first thing I tried was to start Update Manager and apply any patches. Update Manager showed me a list of patches but when I tried to install the updates it failed with the message:

Error failed to fork pty

At this point I wasn't getting warm, fuzzy feelings. Googling for the error messages turned up several Ubuntu bug reports for both problems. Many commenters reported that adding devpts to the fstab resolved the problem for them. So I tried their suggestion and it solved the problem for me as well. To apply this fix you need to add the following line to /etc/fstab:

devpts /dev/pts devpts rw,noexec,nosuid,gid=5,mode=620 0 0

To edit /etc/fstab press ALT+F2 to bring up the Run Application dialog. Then type in either”

gksudo gedit /etc/fstab

or:

gksudo gedit /etc/fstab

After adding the entry for devpts you need to mount it. You can either reboot or you press CTRL+ALT+F1 to temporarily switch to console mode. Once in console mode, login as root and run:

mount -a

exit

After exiting console mode you should now be able to successfully launch GNOME Terminal from the menu. It worked for me anyway.

NOTE: After rebooting, GNOME Terminal would not work again. After running mount -a from console mode it started working. So the problem is only partially solved if I have to manually mount the device after each boot.

No RAID

After the upgrade my RAID volume would not mount. When I tried to mount it I got this error message:

mount: special device /dev/md0 does not exist

I ran sudo mdadm --detail --scan and it showed the RAID array, but it didn't match the entries in either /etc/mdadm/mdadm.conf or /etc/fstab. It turned out that the RAID device had changed from /dev/md0 to /dev/md/d0 in the upgrade. Fixing the problem required two steps:

  • Replace the ARRAY entry in /etc/mdadm/mdadm.conf with the output from sudo mdadm --detail --scan.

    NOTE: If the output contains the phrase metadata=00.90, then delete that phrase. mdadm doesn't like metadata format 00.90 and gave me an error message:

    mdadm: metadata format 00.90 unknown, ignored.

  • Change the entry in /etc/fstab to the new device, i.e. from /dev/md0 to /dev/md/d0.

NOTE: The RAID volume does not auto-mount after rebooting. So this problem is also only partially solved.

No Sound

When anything tries to play sound I just get a crackling sound from the speakers. I'm still working on this problem…


Update: Sound problem fixed.


Final Update: All problems fixed.

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Running vsftpd Behind a NAT Firewall

Saturday, 14. March 2009

I needed to set up a vsftpd server recently but I needed it running behind a NAT firewall. I set up port 21 in the port forwarding table. And it didn’t work. That’s because on Ubuntu 8.10 Intrepid Ibix the vsftpd config defaults to passive mode. I tried changing it to active mode but could not get that to work either. Since passive mode is recommended for vsftpd I went back to trying to make passive mode work. I needed to change vsftpd.conf to set the value of pasv_address to my public static IP address. Then in addition to forwarding port 21 I also needed to forward all of the ports in the range between pasv_min_port and pasv_max_port (inclusive) as defined in vsftpd.conf. In my case that was ports 32000-32127.

vsftpd_passive_ports

After adding that range to the port forwarding table in the NAT firewall it works great. You can increase or decrease the range of the passive ports and you can move it around in the port numbering space to suit your needs.

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