TMBG Day 4

Back to work on the TMBG answering machine. The clock is ticking down. John and John are going to be on the show on Tuesday, so it’s now or never.
I’m going to post my work notes, in case there’s some interest. I’ll turn them into an article for The Screen Savers web site that might be a little more readable. I imagine most of you will want to skip along to the next post, however.

I have borrowed a “voice modem” from Roger. It’s a Zoom Model 3049 – PC V.92 56K external modem with voice capabilities. I have no idea if vgetty will work with this thing at all, but I’m willing to give it a try.

I’ve modified /etc/inittab as indicated in the (sparse) vgetty documentation to start vgetty on boot. I’m kind of guessing here but this seems to work:

S1:S3:respawn:/usr/local/sbin/vgetty modem

Checking the vgetty log file (/var/log/vgetty.modem – which is very helpful and complete) I see that indeed something is happening. Vgetty seems to be starting (amazing) and can even communicate with the modem. But I also see that I’ve put voice.conf, the vgetty configuration file, in the wrong spot. I’m moving it to the correct locale: /usr/local/sbin/mgetty+vgetty/.

Still not seeing voice.conf. I’m chmod’ing it to 666 to give world r+w privileges. That worked.

Now a new error message. There’s no group “modem”. So I’ll create one. I’ll make the root a member of modem. I think the system will always run as root anyway since there’s no net access and no way to hack it. Done. Error message is gone.

The log also tells me that the modem is a “generic Rockwell” voice modem. That’s very encouraging, since vgetty supports the Rockwell chipset. The log says it’s seeing the modem on /dev/modem and the config strings are going through. I’m getting an error however when vgetty tries to initialize the voice modem functions. Uh oh. Sure enough, the modem will not answer the phone. It sees it ringing – the AA light comes on – but it doesn’t pick up. I’m thinking it has a proprietary voice interface. Wish I had a ZyXel lying around.

While I’m pondering that problem, I’ll start working on the scripts to convert the MP3s on the CD into the answering machine message.

First I have to convert a TMBG MP3 into a form the voice modem understands (rmd) using the following programs, SoX, wavtopvf, and pvftormd. The last two come with vgetty, but I have to guess which rmd format to convert to. Probably Rockwell 8-bit, right?


# convert to 16-bit wav at 11,025 bps (that's all wavtopvf understands)
sox happy.mp3 -w -r 11025 happy.wav

# converts to pvf, an intermediate format
wavtopvf happy.wav happy.pvf

# final conversion to modem audio format
pvftormd -Rockwell 8 happy.pvf standard.rmd

This all seems to work, but there’s no way to verify it until I can get a voice modem that works with vgetty. I’m so close, but… that’s enough for today. Time to trick or treat.

13 Replies to “TMBG Day 4”

  1. > Sounds like great publicity for MS. Now you know why ‘regular’ people will never use Linux…
    As I always like to say… If you think Linux is hard to use, wait until you’ve seen Windows…

  2. It always amazes me that people are so quick to put down open source and linux. A number of componets in window’s are borrowed either from linux or open source.
    Example, tcp/ip stack in win 2000, xp, 2003 is the FreeBSD tcp/ip stack.
    The ie browser was borrowed from an open source browser called Mosaic. I suspect that microsoft implementation of some protocols( ex. smtp ) is also based on open source.

  3. “Sounds like great publicity for MS”
    Umm… How many “regular” people are trying to hack together a headless sit-in-the-corner music server answering machine?
    This isn’t a project for “regular” people. I imagine it could be done with Windows, but I also imagine there’d be as much weirdness going on, if not different weirdness.

  4. If you have problems with the modem, Leo, I have an old P1 233 with a Sound Blaster 16 and a Modem Blaster ISA 56K voicemodem (I think it’s a voice modem. Let me find the box) that I can send to you. All it needs is a HD and one ribbon cable to hook the CD-ROM back up.

  5. The majority of Americans are sufficiently overweight as to dramatically increase their risk of all sorts of diseases. Too many Americans invest in loaded mutual funds when academic research and pratical experience shows there is no economic benefit to use loaded funds when no-loads are actually better (lower cost). It goes on and on.
    Folks do not necessarily act in their own economic self interest (i.e. using open source). This illogical and even moronic behavior confounds economists, but its human nature.
    Just because open source is cheaper to impliment, substantially more secure, does not mean the majority will ever adopt it. If we believe the premise that it takes slightly more skill, committment, dedication or brains to use open source versus commercialware, then this is another reason why open source will never replace commercial software.
    Microsoft is to software and security what Mcdonalds is to food and good health.
    L8tr

  6. Make sure there aren’t any “regular” getty’s running on the serial port associated with the modem, too. (check /etc/inittab)

  7. I’ve only built one mod in my life. it was some kind of an electronics tester the details of which have long since gone off the radar. I remember what a thrill it was when it finally worked. I’m sure it wasn’t original but the fact that I made it work was all that mattered.
    Have you noticed Apple dropped the price of the emac with a superdrive to 1099? The emac also has a 99 dollar final cut express option not offered on any other model. I’m on my way!

Comments are closed.