Archive for March, 2013

Media Server Odyssey Part 4: Autorip

March 27, 2013

If you have time on your hands, feel free to start at the beginning.

So now the thing plays music. I also want to be able to update the music supply painlessly. Specifically, I would like to be able to insert a CD into a drive attached to the headless Pi and have it rip the disk, with ID3 tags, and pop the disk without any further interaction.

This is where a flexible solution like a Raspberry Pi starts to come into its own – it doesn’t just play music, like the Streamium or Sonos, it’s also possible to extend it to do anything a Linux box can do. There are packaged devices that play and rip, but they are pretty expensive.

I guess here I’m demonstrating that I’m an ancient crusty person who still buys CDs. I could just buy the MP3s instead and copy them straight to the disk. Meh.

The hardware for CD ripping was easy to come by. I bought a cheap DVD drive on eBay. It’s also USB powered, so my Raspberry Pi media centre (aka giant pile of wires and USB devices) is still driven from a single power socket:


For the software, a tiny amount of googling will identify the best hands-off Linux ripping tool – abcde, which stands for A Better CD Encoder. There are many things I like about this tool:

  1. Command line driven
  2. Configurable, but also designed for use-cases like mine. Some highly configurable tools are very hard to get to do the simple things you want…
  3. Capable of ripping completely non-interactively (the -N switch)
  4. Based on standard tools like lame and cdparanoia
  5. Written in pure bash! In a single 4,500 line script! It’s some of the most transparent Linux software I’ve ever used because I love bash and wallow around in it all day at work. If I want to know how abcde does things, it’s extremely easy to open up the one source file that does the work and browse through it to find the answer.

I found a standard config file for MP3 ripping, which required minimal customisation.

I wanted to use the SD card as the wav file temp space since I thought it might be faster but there wasn’t enough space; possibly there is too much clutter in my install by now. In any case, I’m not actually that interested in how quickly (within reason) it can rip the CDs – I just want it to be easy. Since my media centre sits in my living room, I should be able to gently feed in CDs at my leisure.

The tougher part was getting abcde to launch on CD insert. As always with Linux, there are several hardware event toolkits which succeed each other and all look completely different. The latest in the chronology is udev, but I found that if I ran “udevadm monitor” and plugged in a CD I got no events 😦 Maybe I just didn’t understand the man page – it certainly wouldn’t be the first time.

So I tried halevt. This time, running the monitor command:

lshal -m

and then inserting an audio CD gave this:

Start monitoring devicelist:
21:19:30.866: storage_serial_HL_DT_ST_DVDRAM_GSA_T20L________________________________0_0 property storage.removable.media_available = true
21:19:30.991: storage_serial_HL_DT_ST_DVDRAM_GSA_T20L________________________________0_0 property storage.cdrom.write_speeds = {'4234', '2822', '1764', '706'}
21:19:31.361: volume_part_1_size_472217600 added

I also got useful information about the relevant device by examining the output from lshal, which dumps information about all your devices. There was still a bit of argy-bargy to get the halevt listener/handler configured properly. The first thing I had to do was remove all the default entries, which are all to do with automatically mounting USB drives, something that interfered with my existing mechanism for doing this.

The configuration documentation had some good information, but as usual examples are most useful and I just adapted what was in the default config file. One thing that confused me was that there looks like there is a halevt directory for scripts to be launched from halevt events (/usr/lib/hal/scripts/), but if you put “env > somefile.txt” (note you’ll need to use XML encoding for file redirection operators! It’s hard to put these in my main code examples because WordPress sucks) as your event script, you find that the $PATH is actually just /sbin:/usr/sbin:/bin:/usr/bin. That’s fine – abcde and all its tools are installed there anyway. This was my final config:

<?xml version="1.0" encoding="UTF-8"?>
<halevt:Configuration version="0.1" xmlns:halevt="">
<halevt:Device match=" = true">
<halevt:Property name="">
<halevt:Action value="true" exec="echo $USER > /home/pi/log/abcde.log ; sleep 10 ; abcde -N >> /home/pi/log/abcde.log 2>&1"/>

This has two crucial components – selecting the appropriate event (a combination of the Device match attributes and the Property name attributes) and the commands:

exec="echo $USER > /home/pi/log/abcde.log ; sleep 10 ; abcde -N >> /home/pi/log/abcde.log 2>&1"

This keeps track of what’s happening in /home/pi/log/abcde.log for debugging purposes. I think the $USER is actually root for halevt runs – I probably don’t need this part anymore. Note the sleep 10 – I found that it took some time after the event for the CD to settle and be available for abcde.

It works beautifully – put in a CD and the Pi rips it to the target directory and pops the disk. You just need to wait a little while for the encoding to finish and then update the mpd database from one of the clients – you can do this with mpdroid.

One potential problem was that the disk pops after it has finished ripping the wav files, not the whole process. This means you can rotate the disk straight away and the poor old Pi will have to rip this one while still encoding the last. However, I found it coped perfectly well with this; the Pi can rip one track, encode two others and play MP3s through mpd at the same time. The system load goes up to 5-7, but the Pi soldiers on with no obvious problems. Impressive.

Media Centre Odyssey 3: Architecture Revision

March 26, 2013

Hello, weary traveller. You might want to start at the beginning.

My original architecture used a uPnP Android device with Bubble uPnP and connected to my Bluetooth speaker. It seemed to work fine, but occasionally it would drop out for up to a minute at a time. Now, the problem of debugging this. It could be:

  1. The Pi not supplying the file fast enough
  2. The Wifi not supplying the file fast enough
  3. An encoding bottleneck on the tablet
  4. A Bluetooth problem communicating with the speaker

I could hardly believe the supply of a small MP3 file could cause the problem, but on the other hand local files on an Android device played over the Bluetooth without problems. This was also a frustratingly intermittent problem – sometimes it would play for over an hour with no blips.

I also tried changing the architecture slightly by installing mpd on the Pi and using mpdroid on the Android device. I used the mpd http stream support to play the music on the device and pipe through Bluetooth onto the speaker. In this scheme, the Pi is acting as both storage and decoder, with the tablet as controller but also a conduit from the Pi to the speaker. This architecture is the most complicated yet, and even more intermittent. I heard from the Bubble uPnP developer that http streaming on older Android devices like my HTC Desire was buggy and I should upgrade.

But this seemed like hard work and I thought the number of moving parts in this solution was bound to have problems. I also still didn’t like the dependency on a conduit Android device that was subject to battery life (or, for example, the person with the phone wanting to leave the house). Time for a rethink.

Although the http streaming didn’t work, I really liked mpd, which has server-side playlist you can control from multiple client devices. The mpdroid control is a fully fledged smart-phone remote controller with the ability to edit the upcoming tracks and search for the music you want to play. Also, the search is fast; my 10,000 track collection usually returns from a search in under a second. You can also use a software volume control that you can, again, access from the remote if you uncomment this line in the /etc/mpd.conf

mixer_type "software"

It was time to relax one of my previous constraints, that the Pi should be sited anywhere. If I sited the Pi next to the speaker I could connect them with a robust and easy to debug technology – a wire into the 3.5mm audio jack. Multiple Android devices, each with an mpdroid install, could control the playlist. Having connected all this together, I was very pleased – it all seemed to work! The remote was easy enough that I could install it on my wife’s Android phone and she actually felt able to use it!

Unfortunately, the solution was still not perfect. I found that when the volume was turned down too low, the sound quality became very poor. I spent ages trying to change drivers and tune ALSA (which is bloody awful, by the way) on the Pi. I’d even gone as far as assuming my Pi was broken and ordering another when I found out the answer. The Pi is not meant to have high quality audio through the audio jack. Of course.

The solution, apparently, is to buy a USB sound card. So I tried this one, reported by lsub as:

C-Media Electronics, Inc. Audio Adapter (Planet UP-100, Genius G-Talk)

It kind of worked, but was fuzzy. I tried a lot of hints I found online, including this and some of this but it was still fuzzy. Then I bought this only to find it contained identical hardware. Argh! Then I tried this (notice how I’m gradually getting more expensive), but when it arrived it reported as this:

C-Media Electronics, Inc. Audio Adapter

Argh again! It looks the same! However, this one works without fuzziness. I only had to buy three sound-cards to get there. I also had to do this in /etc/modprobe.d/alsa-base.conf:

options snd-usb-audio index=0

and this in /etc/mpd.conf:

audio_output {
type "alsa"
name "USB Audio"
device "hw:0,0"

So now, we have a completely working high-quality audio jukebox, controlled from multiple remotes that are easy enough my wife can use them. Of course, this might now seem moot since you can get a canned Raspberry Pi distribution that does this. But I’m not done yet!

Media Centre Odyssey Part 2: The Hardware

March 25, 2013

If you’ve arrived in the middle and want to read the whole story, you can start at the beginning.

The core of my media centre is the Raspberry Pi that stores and supplies the music files. Although the Pi is cheap, it comes utterly bare. You can think of it like buying a motherboard, memory, procesor and graphics card: it is the core of what you need, but is quite a way from being a full computer.

Alongside the Pi, I also need:

  1. A Power supply. To start with, I used the power supply from my HTC Desire but later used a powered USB hub – see below.
  2. An SD card for the operating system. I have one 4GB and one 8GB and the 4GB is a bit on the pokey side. I recommend 8GB.
  3. A hard drive for the music. I started with one with an external power supply, but I really wanted the Pi to run on a single power socket. There are plenty of cheap-ish USB drives now that are powered from USB only, although you will need a powered USB hub. I have a 750GB drive.
  4. A wifi dongle. I tried a few that might have worked in theory but after several evenings fruitless module bashing were not working. I ended up with a “Mini Nano 802.11n” (very generic name) which was cheap and worked out of the box. It reports itself (lsusb) as “Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN Adapter”. They can also be powered by a Raspberry Pi without a powered hub, which will be useful for satellite players.
  5. Depending on what came with your other peripherals, you will also probably need a fistful of cables of all shapes and sizes (HDMI, USB, audio…)

Also useful:

  1. A screen, for the first time you boot the Pi to get ssh setup. Possibly, you can get a Raspbian image that will just boot with ssh switched on so you can go headless from the get-go.
  2. A keyboard. I bought a weird floppy thing (and a keyboard, snigger) which is really horrible to type with but folds up small for storage (so does the keyboard, snigger again. OK, enough sniggering).
  3. A case for the Pi, if I don’t want the bare board sitting around. I bought one of these snazzy plastic things. Ths is nice, but if you have a USB hub and a hard drive, you still have a really messy pile of components so the case on the Pi itself doesn’t really help much.

As well as all the core stuff, you also need a USB hub. The Pi has 2 USB ports, which is enough for Wifi and a USB hard drive, but it can only power very low-power peripherals, so as soon as you ask it to run a few USB devices you need a powered USB hub. Luckily, you can also power the Pi itself from the USB hub. The Pi is a sensitive beast, and with the wrong power supply or an unreliable connection, it will crash often especially if you wiggle the cables by moving the Pi while it’s on.

The hub is the thing I had the most problems getting right. I started by buying an anonymous piece of crap on eBay and the Pi crashed all the time. Then I bought a recommended device, which worked for a while until I couldn’t find the power supply for it, plugged in the wrong one. Then there was a nasty smell and instead of a USB hub I had a smouldering little plastic brick. I bought another one, but even then either the Pi or the hard drive plugged into it kept giving up. Also, the later stages of my project used more and more USB ports and it didn’t have enough. Finally, and I don’t want to get precious about this, but it felt really cheap and nasty. So I bought a bigger one on eBay. This thing has more ports, is cheaper and even feels nicer than the one on ModMyPi, so I recommend it.

This is where you see that the Raspberry Pi project can become a bit of a non stop buy-a-thon. I’ve already spent more just on USB hubs than I have on the Pi itself. On the other hand, all the bits and pieces are fairly cheap on their own and if you move slowly and you’re happy to piss away £10 a month on a tinkering project I guess you can probably justify it. At least I’m not pimping my car or anything.

If I cost up the stuff I really needed for this part of the project it looks roughly like this, including postage:

  • Pi: £35
  • SD Card: £8
  • Hard Drive: I blagged one from somewhere else, but you can get one for about £50
  • USB hub: £5
  • mini-USB power cable: £2
  • Wifi dongle: £5

So that’s £105. If I add the keyboard, case and extra cables it’s maybe another £20-25. If I add all the stupid other crap I bought and it didn’t work, about another £40. So more expensive than buying an AppleTV, then. Sigh. But more “fun”! Sigh again.

Anyway, wiring up all this lot, what you get is a bit of a mess, but it does work:

Pi Media Centre: v1Pi Media Centre: v1

So from top to bottom, there is a single plug; the USB hub, the USB-powered hard drive and the Pi itself in a snazzy case. You can see the Pi is plugged into the hub twice, once to provide the Pi with power and the second time to connect the Pi to the other devices plugged into the hub. You might also be able to see the tiny wifi adapter, plugged into the bottom left slot on the hub. These things are very small, which is both good and bad, I guess. I once lost one when it was stuck in one of the holes on the case.

This is a bit of a mess, but with the current architecture I only need wifi and power so I can site this anywhere it can reach a socket. It can be in the bottom of a draw and I never have to look at it. Unfortunately, as I will explain in the next installment, that architecture needs to be modified so that I need way more devices, way more wires and to site it somewhere specific.

Media Server Odyssey Part 1: The Architecture

March 24, 2013

This is part of my Media Server Project (odyssey!). You might want to start at the beginning.

It was only after I started thinking about this problem that I realised how complicated it could be. A media player actually has four separate components:

  1. The Storage, which holds the encoded music.
  2. The Decoder, to translate the stored music.
  3. The Renderer, which actually makes the noises. I guess a purist might separate this into amplifier and speakers.
  4. The Controller, which allows the user to choose the music. This usually includes a visual display and some buttons to press.

As an example, in an old-fashioned integrated CD player, the storage is a CD; the decoder is inside the device somewhere and it’s rendered through and internal amplifier and the speakers; the controller is probably an infra-red remote control but you also have some crappy LCD display telling you what track is playing and so-forth.

An iPod is actually pretty much the same – everything is contained in the fancy unit you buy from Apple. The only difference is that there is a degree of faffing to get your music (from CDs or the web) and then upload it onto the hard drive of the iPod. Also the controller part involves less manual changing of media (storage) than a CD player.

It’s only when you start to put one of these things together for yourself that you realise you are responsible not only for each component, but also for the linkage between components. In your integrated player this is all invisible inside the device but building your own means worrying about wires or wireless protocols connecting each piece and all the potential problems there can be at each stage.

At the storage stage, a digital media centre (thing) is probably based on a hard drive (or maybe SD card or SSD? That’s probably too small/expensive though). That’s great – now you need to plug the drive into something and serve it. In my case I’m going to use a Raspberry Pi running Linux of some kind, but I still need to export the files. I could do this with a Samba share but then I’ll need something that can mount that – probably another PC-grade device like another Pi. A better choice might be to export the files with uPnP or the more advanced/less general DLNA and then another device can consume those files. The auxiliary benefit of this is that I also serve media other than music, of which more later. Of course, there are then many choices of uPnP/DLNA servers that run on Linux.

Quite a few devices can consume music from uPnP, including a smart phone (I have a crappy old HTC Desire), tablet or even a fancy TV. Or, of course, another Pi – they only cost £30 after all. So I could serve the music and play it on my phone using a uPnP client like Bubble uPnP (which is a cool app by the way, although the search is a bit slow. Maybe that’s a server-side problem). Bubble uPnP has an interface to search, queue up and play music, so this use of uPnP has the phone doing the decoding and the controlling. Then I guess I could plug my phone into my old CD player. This would work, but if I’m going to have a device tethered to a CD player I might as well just use an iPod.

One alternative is to use XBMC, which is integrated media centre software that runs on Linux. There is even a Raspberry Pi XBMC distribution. It’s actually a very polished product and looks great, but as far as I could tell, it’s really not designed to run without a monitor (to do the “controller” part). You can download an XBMC remote control for Android and this thing confused me for a long time – it’s actually designed to operate a bit like a remote mouse to control what you can see on the XBMC interface. This makes perfect sense if you’re expecting the display to be on all the time, like if you’re XBMC device is supposed to be playing videos, but I would really like my Pi to be headless (no monitor), if possible. This is how you might expect a plastic-and-rubber remote control to work, but having a smart phone which has a screen and a keyboard work as just a cursor control seems to be missing an opportunity. Feel free to Email me and tell me I got it all wrong.

Anyway, my first design went like this:

  1. Raspberry Pi running Raspbian with a USB drive full of MP3s. There were some hardware complications with this, which I’ll come back to later.
  2. Minidlna to serve the files. I also tried MediaTomb, but I found it a bit slow and I thought the web interface was awful. I’m an old Linux nerd and I prefer text config and log files. The Pi with minidlna constitutes the storage.
  3. A reconditioned Galaxy Tab 2 Android tablet I got for £200 on eBay. I guess it must be one step behind the curve, because that seemed like a good price to me. I guess I’m just not sophisticated enough to know any better. This has Bubble uPnP installed on it, so it’s doing the decoding and controlling.
  4. A Creative ZiiSound D5x Bluetooth enabled speaker that was going cheap on Amazon. This is the renderer.

So as you can see, not only do we have quite a few technologies involved in the components, but we also have USB, WiFi and Bluetooth linking the components. Complicated. The good thing is that the whole thing is wireless, which is convenient. I can site the Pi wherever I want – in a cupboard or something – provided I can wire it into my home network, probably with wifi (more on that later). The only problem is that it’s not as flexible as I might like – if the tablet is reading and playing the music, it can’t be controlled unless you have the tablet. If the table runs out of batteries, it stops playing.

Did it work? Stay tuned.

Home Media Centre Project: The Odyssey Begins

March 22, 2013

I’ve always liked the idea of having lots of my music available at the same time, rather than listening to just one CD at a time. I owned a 3 CD changer and then a 5 CD changer 5cdchanger, one that made a noise like a car-crusher when it changed disks.

When I first saw an MP3 player advertised on Slashdot, I was very excited. It had a whole 6GB of storage! Imagine a shuffle on that!

When I finally got an iPod I was very excited about it and I was one of the sad bastards who had his name laser engraved on the back. It was a cool piece of kit, and it was great carrying your whole music around you. However, I was still missing a user-friendly living room music solution with a remote control and the ability to choose the music without being tethered to the speaker.

Time passed and eventually I had time to think about this in earnest. I felt sure that since portable MP3 technology was so well developed, there ought to be able to buy a cheap-ish solution for the home too. I wanted something with a central music store and the ability to fling music out to all my existing stereos, with central control and the ability to have different or shared music in different rooms.

There were solutions you could buy, but most of them were rather expensive and/or had proprietary components that tied you into a particular provider – things like the Streamium or later the Sonos. The other problem was that these devices often required a media server, and I wasn’t prepared to have a power-hungry buzzing server in the corner of my living room.

Of course, the really easy way to implement this would be to geneflect towards Cupertino and buy Apple. Just buy Apple TV, Airports, iTunes, an iPhone as a controller and use AirPlay. Job done. The trouble is, despite buying an iPod (in 2004, when I was young and naive) and owning a Mac, I don’t like Apple very much, especially iTunes. They want to own what you do and they tell you how to do it. There is a loss of control. Even though it would be much, much easier to go this route, I’m stubborn. Screw Apple.

I decided that if no decent system existed I would build one myself. I would use a low-cost low-power PC like a SheevaPlug, perhaps with satellite receivers of some sort and install Linux on goddamn everything. The full power of a flexible operating system at every node and full control everywhere.

Then the Raspberry Pi came out which was abso-blooding-lutely perfect for this kind of project. There was a bit of a wait before I could buy one, but then the project could begin in earnest.

From One Thing to Another

March 22, 2013

I stopped working in my old job and started working in a new one in commercial world. I stopped making posts because I wasn’t sure what I’d be able to say and also in this job I don’t have much spare time.

Anyway, this means I’m going to repurpose this blog to describe my hobby projects. It’s still Linux and hacky ranting, so it’s not much of a deviation anyway.