Posts Tagged ‘OSS’

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Radio station across town

2010-10-01

Recently, I’ve been heavily involved with the transition involved with moving the radio station out of its downtown office and into the new office known as Burnt Mill. Here are a few things I’ve done lately:

– Wrote a console peak meter.
It’s desirable to avoid running an X11 server, and imperative to never put any critical server processes on top of it. The GUI is a nice tool that has its place, but for a system to boot quickly, it must only perform the necessary tasks to revive critical services (in this case, audio streaming). On a similar note, my systems should probably migrate from ext2 to ext3, since journaling will mitigate time lost to running filesystem check (fsck) every twenty-third boot.

I first did a prototype using #!/bin/bash but was unsatisfied by the load placed on the processor. As it turns out, if you use C you don’t have to open and close the device four times every second. You can open it once at runtime and then just use ioclts to get info from the device. My approach was then to take the existing code base of OSS 4.x (Open Sound System — the acronym is ambiguous since it also refers to Open Source Software), modify ossmix.c in place and recompile. By trimming all methods related to write operations, and all unnecessary constants related to objects other than VUMETER, I was able to easily port the shell scrpit’s echo commands which were written using ANSI for colors and some box-drawing Unicode glyphs. I have yet to develop a method to detect whether the shell supports Unicode, but I have gotten some funky results using Putty’s default translation settings (ISO-8859-1). ASCII art using apostrophes, full stops, and hyphens should be sufficient for most.

– Increased latency on the Delta 1010 connected to the on-air system
We’re using a combination of FMPEG and VideoLAN Client to transmit audio from point to point and have had a lot of “audio output is starving” messages. At first, it was packets being dropped. After notifying our provider, they did some investigating, and I haven’t seen any UDP checksum errors since. However, the drivers must communicate effectively with the applications, and must be scheduled accordingly. By changing the /usr/lib/oss/conf/oss_envy24.conf to have envy24_nfrags to a lower number, I reduced the number of messages logged about starving by an order of magnitude.

– Found out that Shoutcast is now being heavily claimed by AOL
Apparently they want royalties for licensing the official Fraunhofer MP3 encoder in order to use their software, and they don’t want VideoLAN to have Shoutcast capability due to licensing conflicts. I could go ahead and use the old version of the software that has been running for over five years on an older machine, or I could move to Icecast which is open sourced.

OSS has its advantages, such as troubleshooting USB drivers. We have a Behringer UCA-202 that we’re trying to use as an audio input to the streaming server. Of course I’d be much happier if it just worked, but OSS has just recently gone open source [again], so I’m prepared to contribute when necessary. By taking the suggestion to modify the src/kernel/drv/oss_usb/ossudb_audio.c file’s write_control_value function to return 1; things started to work (somewhat). Unfortunately the sound card is locked to 48000 sample rate, and my version of Shoutcast expects 44100/16/2. There remains work to be done.

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Recent development

2009-03-25

Lately I’ve been learning new languages, Prolog being one of them. The problem with blogs is they need to be updated every now and then, and I don’t intend to do so in the most timely manner, but I will from time to time dump stuff here that seems important.

Current projects include:

  • Traffic on Demand (TOD)
    • Primary technical consultant
    • Network / Database administrator
    • Software developer
    • System engineer
  • UNCW
    • Grade student project and attend lab on Friday
    • Work with Eddie (the sysadmin)
      • FOG Server
        • Hoping to deploy before the summer’s up onto a decent server with the blessing of campus IT division which controls DHCP
      • Sysprep
        • Get it working for multiple hardware
  • Personal synthesizer project (dnbMedia)
    • Hardware
      • Desktop
        • Windows XP 32bit – 2.4 GHz – 2GB RAM
        • Presonus Firepod
        • Fostex 5″ stereo set and 8″ sub
        • Balanced cables
      • Laptop
        • MacBook – 2.4 GHz – 2GB RAM
      • M-Audio Keystation 88es
      • Behringer BCR-2000 rotary controller
    • Software
      • PortAudio
      • RtMidi
      • wxWidgets
      • libsamplerate (SRC)
    • Next steps:
      • Incorporate a filtering library
      • Needs more foundational structure
  • Software Engineering project
    • Reengineer UML diagrams from written code for TOD
  • Symbolic Artificial Intelligence project
    • Russian Language translation
  • Systems Simulation project
    • Simulate before and after computerization of operations for TOD
  • Carolina Christian Radio
    • Keep audio programming up to date
    • Server manager

I’d like to contribute more to the open source software community, but the problems I’ve encountered have been the typical “I can’t get it to work on my computer” issues that plague much of software development in general, or a complete lack of communication from some authors.

I was at an engineering conference not too long ago, and met some very interesting people. I have not studied under the engineer track, but I have known many engineers in my day, and have learned from them how things are to be done. I consider myself an engineer to some degree, given my level of involvement and background with technology, and the broad level of support that I offer my clients.

My phone is an LG Dare, which I selected for its simplicity and touch-screen usability. It offers audio and video playback and some other decent features, but it disappoints me in that I cannot develop software that will run on it. I could hack it to run some flash, but honestly I have no desire to relearn flash since it wouldn’t be very rewarding. It has an Alarm-only mode, which is my favorite element; no waking me up these days! The “waking me up” tier of support is not currently offered but can be made available for an additional fee.