Ad Terras Per Aspera

How to send audio between two Linux computers using netcat

Apparently there is no dead simple way to send audio from one computer to another in a low(er) latency way.

Can’t beat this, works for any ALSA app that you can change the output for (or just change your default in .asoundrc).

On source computer:
modprobe snd-aloop
arecord -f cd -D hw:Loopback,1,0 | netcat dest 1234
mplayer -ao alsa:device=hw=Loopback.0.0 something.mp3

On destination computer:
netcat -k -l -p 1234 | aplay

Update: Oh, and apparently you can do this in Windows, too.

Linux layer 2 bridging can’t do Firewire

Well, it seems and the Linux kernel can’t bridge dissimilar network types, which means I can’t bridge Ethernet and Firewire (workaround until I replace my NIC in my desktop because it fried, having my laptop route for my desktop).

My laptop’s IP is 192.168.2.4
My desktop’s IP is 192.168.2.2
My router’s IP is 192.168.2.1

So, the work around seems to be this…

On the laptop, with eth0 already up:
ifconfig firewire0 up 192.168.2.4
route del -net 192.168.2.0 netmask 255.255.255.0 dev firewire0
route add -host 192.168.2.2 dev firewire0
iptables -F
iptables -P FORWARD ACCEPT
echo 1 > /proc/sys/net/ipv4/conf/all/forwarding


On the desktop:
ifconfig firewire0 up 192.168.2.2
route add default gw 192.168.2.1

To make this permanent, you would edit /etc/networking/interfaces like this…

On the laptop:
auto eth0
iface eth0 inet static
address 192.168.2.4
netmask 255.255.255.0
broadcast 192.168.2.255
gateway 192.168.2.1
post-up ifconfig firewire0 down
post-up ifconfig firewire0 up 192.168.2.4
post-up route del -net 192.168.2.0 netmask 255.255.255.0 dev firewire0
post-up route add -host 192.168.2.2 dev firewire0
post-up iptables -F
post-up iptables -P FORWARD ACCEPT
post-up echo 1 > /proc/sys/net/ipv4/conf/all/forwarding

On the desktop:
auto eth0
iface firewire0 inet static
address 192.168.2.2
netmask 255.255.255.0
broadcast 192.168.2.255
gateway 192.168.2.1


USB 3.0 works under Linux

I decided that I needed a real backup solution, even though I have a RAID 5 for file storage in my workstation; maintaining a backup of a 2TB array is a pain in the ass if all you have is blank DVDs.

So, I purchased a Vantec NexStar 3 SuperSpeed (NST-380S3) enclosure, a Samsung EcoGreen F3EG 2TB 5400rpm (HD203WI) drive, and a USB 3 PCI-E controller.

It seems the only shipping USB host controllers the moment all use NEC’s USB 3.0 chip, and almost all the PCI-E boards look alike. They all seem to run in the $25-45 range. The great part is Linux supports NEC’s controller as of 2.6.31. The controller worked with no configuration soon as I put the card in.

I chose that specific Samsung drive because it seems to be the only sane 5400 rpm 2TB drive out there. The only other choices were Seagate’s new 5900 rpm drives (which, according to independent reviews on Newegg and enthusiast forums have an unacceptably high failure rate, very unusual of Seagate), and Western Digital’s Caviar Greens (which are 5400 rpm, but suffer from obsessive head parking which is apparently leading to premature drive failure).

Several reviews peg the HD203WI at an average of 90mb/sec writes for sequential writing, or about 2-3x the speed of USB 2.0.

mkfs.ext4 took 7:44 minutes to create the file system (while iotop confirmed it was doing in excess of 100mb/sec writes for much of the process), and hdparm -t /dev/sdx also indicates the drive in this enclosure can push 100mb/sec.

After writing to the drive for an hour straight, the enclosure is warm but not hot, and after removing the drive from the enclosure, the drive itself is warm; this is compared to the Seagate 7200.12s in my RAID 5 array which could burn you at this point.

Many drives fail in enclosures because they overheat; I don’t think this will happen due to Vantec’s thick aluminum design in the NexStar series enclosures, and the fact that the HW203WI has low power usage.

After formatting with ext4, the file system uses 29GB out of 1.82TB total. Its kind of funny when I’ve owned drives smaller than the space consumed by an empty file system.

I’m rather happy with my purchases overall.

Approximate Youtube Bitrates

I’ve been wondering what bitrates Youtube produces on files, but they don’t upfront say.

New videos are encoded in eight formats. However, due to bug in Youtube, some 24 fps videos (such as those from film sources) will have duplicate frames inserted to make them 30 fps, causing a very noticeable jitter approximately twice a second.

Note: This does not include WebM videos yet as the support is still experimental, and Youtube is not yet encoding videos in 1080p, only 720p (format 45) and 480p (format 43).

Now lets see how a couple high quality videos fair on Youtube.

With these 3 popular HD videos, its easy to tell what sort of bitrate Youtube tries to hit.

SLF4J and making JUL shut up

I’ve decided to switch to the Simple Logging Facade for Java (SLF4J) plus Logback to bridge java.util.logging (JUL), Log4J, and Apache Commons Logging all into one log output.

Problem is, JUL won’t shut up. Frameworks that log to JUL output the log to the console, and then SLF4J repeats it right after. However, putting this code in before running SLF4BridgeHandler.install() seems to fix it:

java.util.logging.Logger root_logger = java.util.logging.LogManager.getLogManager().getLogger("");

java.util.logging.Handler[] root_handlers = root_logger.getHandlers();

rootLogger.removeHandler(root_handlers[0]);

Now I get one single log output alone.