Sunday, July 14, 2013

Internet Radio Podcast, the Raspberry Pi Edition

I recently bought a Raspberry Pi*, the small-and-cheap-but-powerful computer taking the geek world by storm. The hope is that someday I can use this little board or its successor to teach my baby daughter more about my own interests. But given my current time constraints, I figured I should get one now to ensure I've done at least one significant project with it by the time she's old enough to grok what this thing is.

That's right; I think I can do one useful project with my Pi in the next ten years.

People go crazy with their Pis: rigging up their microwaves to cook food according to the bar code on ittaking pictures from very very high in the sky, and building souped-up irrigation systems that would be the envy of pot farmers everywhere.

I do have ambitious goals in mind, but I wanted to start with something a little simpler. Some of you may remember my Rube-Goldberg-esque "Radio Broadcast Podcast." An obvious failing of my original setup was that it required me to leave my MacBook running. Predictably, this has turned out to add enough friction that the recordings don't get made.

At the time, commenters offered suggestions to fix that obstacle. One was to set up an EC2 server that could run all the time. A good idea, and I'm certainly comfortable with EC2, but I never got around to it. Between launching a big game and having a baby, the priority on the whole endeavor kept dropping. Still another suggestion was to just buy a server for the home. A very good idea, but we didn't have space for it even before we had a baby.

Enter the Raspberry Pi. Since it's just a normal computer that runs Linux, it can also be a server. Not a super-powerful one, but I don't need a super-powerful server for my house. And it's hard to argue with the physical footprint: the Pi and its case are roughly the same size as two or three stacked decks of cards. I just tucked it into a small space behind our TV.

I decided to start from scratch on my radio-to-podcast scripts, mostly because I wanted to fix some problematic and error-prone behaviors from version 1. It ended up being a few independent parts:

  1. A Python script runs every five minutes as a cron job and uses a config file to determine if it should be capturing streaming audio. If yes, and streamripper isn't running, it starts the program, figuring out a file name based on parameters in the config file (including adding numbers if a file of that name already exists.)
  2. Another cron job looks in the download directory for any mp3 files that haven't been touched in 5 minutes, uploads any it finds to S3 via s3cmd, and then deletes them.
  3. Yet another cron job creates a podcast-compliant XML file by getting a listing of items on S3, running them through an awk script that generates the necessary XML, and then taking that output and uploading it to S3.
This may still seem Rube-Goldbergian, but it's designed to be more resilient than its previous incarnation. If streamripper crashes or the network goes out, my script will ensure that the music starts recording at the next opportunity and it won't overwrite the first part. If the Pi can't get to S3 for some reason, the files will stay in place until needed. There's no cleverness around updating the podcast xml file; it's created from scratch every time. (Note that doing a bucket listing on S3 very much exposes you to eventual consistency issues, but even a day's worth of latency is probably fine for my purposes.) 

The onus is still on me to clear old files from S3, but that's something I can do every few months. And once I do, the XML file will reflect that within an hour.

The next step is to run an HTTP server on the Pi so that I can log in and make configuration changes from any of the devices on the network instead of sshing in and modifying the config file directly. And after that? I'm tempted to add AirPlay capability so that if I happen to be home and awake, I can send the current download to the living room speakers.

Overall, I'm pretty impressed with the Pi's capabilities. I doubt I can pile too much onto it, but I'm curious to see what its actual limits are as a household server. Future projects involve using its ability to talk to other electronic components, which is one area where the Pi shines.

* I bought the Maker Shed Starter Kit. It comes with a good book and most of the stuff you'll need to get going and do the book's exercises.

Tuesday, July 9, 2013

Screen Time

This is a bit of a tangent for a programming blog, but I figure this is a relevant topic for many people reading this blog.

The TL;DR review: If you're interested in kids and how they interact with media, buy this book.

I love technology. Probably more than most non-technology people really understand. I love its potential, the changes it makes to the world, and the ideas that drive it forward. And I look forward to sharing that love with my baby daughter. Some dads can't wait until their kid can go to a baseball game; I can't wait until she is able to grasp that technology is a thing within her ability to control and mold. And the day she expresses an interest in controlling that technology herself? They'll be able to see me smiling from the International Space Station.

That's not always a popular view here in Hippyville, USA, otherwise known as Berkeley. Paradoxically, a casual drive from some of the biggest tech companies on the planet, there is a pervasive notion that mixing technology and kids is bad. One extreme -- Waldorf schools -- came up in conversation with my wife. Here's an excerpt from

"Waldorf teachers are concerned that electronic media hampers the development of the child's imagination. They are concerned about the physical effects of the medium on the developing child as well as the content of much of the programming."

While I think Waldorf has some good ideas, that first sentence sent me into a fury. You can't lump all electronic media together unless you're driving your philosophy through some misguided notion that "things were better in the old days." I'm not going to argue that Angry Birds or Robot Unicorn Attack is good for a kid's development, but I know of plenty of apps and "games" that are all about imagination. And I feel that the Waldorf view actually cuts off areas of exploration. (Let alone its effect on kids who, let's face it, are coming of age in a technology-driven society.)

But what do I know? Just what I feel in my gut. One article I read about kids and technology suggested a book called Screen Time, by Lisa Guernsey (the title seems to be messed up in the database), so I bought it.

In the end, she says, there's no easy answer. But she has a recurring theme she's derived from her research that she applies to her own children: What content is your child seeing, what context are they seeing it in, and where is your individual child in their development? Are you destroying your kids by letting them watch TV while you shower? No. Are there long-term downsides to media access if parents aren't careful? Yes.

The book focuses heavily on television time, which is less relevant to me since we rarely watch TV or even have it on. Her epilogue notes the emergence of the iPad and its potential, but there's precious little research about it so far (however, it does solve one problem with previous incarnations of interactive toys: the abstraction needed for "I press this thing on this thing way over here and the screen does something.") She does list links to sites that do thorough reviews of children's interactive media, however. My favorite is Children's Technology Review.

Still, the book is full of eye-opening explorations of the research that's out there, which she has extensively plumbed, as evidenced by her endnotes and massive bibliography. She divides the book into chapters that each address a prevailing question about kids and screens: What Exactly Is This Video Doing To My Baby's Brain, Could My Child Learn From Baby Videos, My Toddler Doesn't Seem to Notice When the TV is On - Or Does He? And so on.

Here were some of my key takeaways, in no particular order:

  • TV is not turning your kid into a zombie through passive engagement. She says that the research that argued that (heavily cited by another book on my queue, Waldorf-darling Endangered Minds) has been widely debunked. Kids engage heavily with what's on screen, trying to understand it.
  • The standard advice by the American Association of Pediatricians about no screens before two years old? Not really based on any research.
  • TV does reduce creative play time and time with parents.
  • TV in the background is a bad idea. It exposes kids to adult-themed content and makes it harder for them to develop language skills. Make it a foreground activity when it's on. (And only do short, controlled watching times. Most parents paying attention have a "you can watch this half-hour video and that's it." mentality)
  • Telling your toddler that something scary on TV or in a movie is "not real" is useless. They're toddlers; everything is real.
  • If your child has an interactive electronic thing, you will naturally steer towards saying, "Push that button now, or don't do that yet." Don't. Let the kids explore on their own. Also, most interactive media sucks: It imposes artificial constraints on what can and can't be done at any moment. There are plenty of apps that don't fall into that trap.
  • Dora the Explorer is awesome for kids. So is Sesame Street, Mister Rogers, some show called Dragon Tales, and, yes, even Barney.
  • Purveyors of products that purportedly improve your kid are rarely based on real research. But it is possible for kids to learn from DVDs and the like. Choose wisely.
  • Kids' brains are weird.
  • Products and shows often have very specific age ranges they're aimed at. Pay attention to those (but note that publishers will often advertise a wider audience to get more sales.)
  • Your involvement is important. Not just in a "Are you having fun" way but in a "what did you think of this or that?" Engage your kids about what they're seeing.
  • Moderation is important: Video entertainment is just one facet of experience (duh.)
I can't praise this book highly enough. The author has had the ability (helped along by various grants) to really dig in deep. She looks at academic research, talks to scores of parents and social workers, looks at her own kids, and tries to shape what little material is out there. 

It's possible that I highlighted more of this book than not.

Sunday, July 7, 2013

DSByte: Scala-based DSL for binary data structures

About a year ago, I wrote about a tool for creating binary structures more easily. It was inspired by Erlang's binary packing syntax, and was for a scenario where a server was creating small binary for a client that didn't speak Java (i.e., so simple serialization wasn't a possibility)

I recently decided to recreate it, but this new version is a whole new beast. It's still inspired by Erlang's syntax, but I'm enhancing that syntax, I rearchitected it, and I wrote it in Scala.

The very early version of DSByte, as I call it, can be found under my github account. It currently only supports packing from objects into binary, but I'll add unpacking from binary into objects soon.

One of the things I like about Scala is built-in support for simple DSLs, and this was a good opportunity to exercise that feature. While the parser combinator feature takes a bit of getting used to, it's quicker and friendlier than ANTLR, though it's also less powerful. But for my need, it fit the bill nicely.