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Chris Boyle

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On the inability of smartphones to bilocate (a short review of recent purchases)[Jul. 4th, 2008|09:35 am]

I don't particularly approve of the apparent extinction of no-frills mobiles, but I'm one of those strange people who actually find smartphones (at least the ones that are at all smart) useful, simply because I'd otherwise carry a PDA and a phone. Unfortunately, on those occasions when I want to use both functions at once (e.g. a phone call involving looking at my calendar) until recently I found myself switching awkwardly between phone-to-ear and phone-in-front-of-me where I can see the screen. Obviously, having a headset solves this, but for most of my day I'm at my desk wearing headphones, listening to music, so to take those headphones off and, either at the start of the call or during it, put on different ones, is doubly inconvenient. Enter the A2DP device I mentioned previously, and some convenient headphones built into a lanyard.

Motorola S705

This device is supposed to solve the above problem by making up to two Bluetooth connections at once: one using the headset/handsfree profile for low-quality audio with a microphone, and one using Advanced Audio Distribution Profile (A2DP) for stereo audio; it will then switch from the A2DP source to the phone on ringing or an outbound call. This switching must take place even if the A2DP source is the phone itself (which my Treo can be, with Softick Audio Gateway), because A2DP doesn't carry a microphone signal. Music from the Treo is somewhat of a special case though: Softick disconnects the headset profile when I start listening to A2DP; when a call happens, any music player on the Treo will stop automatically, and the phone will reconnect to a Bluetooth headset if Bluetooth is on, meaning that the Treo handles the switch rather than the S705, and this works fairly reliably. There is a delay of a few seconds after the call before the music resumes.

Results connecting Ubuntu to it have so far been mixed (I haven't touched Windows Bluetooth stuff for years, so I've no idea how well that would work). The connection can be established from either the PC or the device (which has an LCD and a menu of paired devices) and establishing it from Ubuntu (by starting to play some audio to an appropriately-configured ALSA device) often seems to result in lagged and intermittent audio, which seems like it ought to be a fixable software bug. I'll file it, presumably against bluez-audio, when I've made a better attempt at nailing down exactly when it happens. Establishing it from the device works well, but one must then start playing audio before some sort of idle timeout (I don't know which end, but it's about 10 seconds) gives up and disconnects it again. This is somewhat fiddly.

Switching to a phone call can also be problematic when a PC is still playing music: I have at least once had a choppy, buzzy sound affecting the audio in both directions until I disconnected the PC. I'm guessing that there is still an A2DP stream connected when this happens, and the device wants to keep it connected so it can switch back to it after the call, but lacks either sufficient clock cycles or sufficiently clear Bluetooth spectrum (this was an office with at least 10 Bluetooth devices nearby) to succeed without affecting the call.

If you're going to use ALSA to drive a device like this, I can recommend PulseAudio: the set-up is described on, but I've changed the profile to "hifi". Using Pulse will allow you to play sound from multiple applications simultaneously, as dmix doesn't seem to play nicely with the ALSA bluetooth module.

One more feature I haven't mentioned yet: there's an FM radio, using the headphones as an antenna, which works reasonably well outdoors in Cambridge. When there isn't an A2DP connection, it can be turned on with one button; it can also be muted with the same button (I hate ads). Switching between FM and a phone call works perfectly. There's RDS to show the station name on the LCD, but it usually takes long enough to work that I've decided whether I like the station already from the audio.

Overall verdict: like most of the hardware I use, this has quirks (waily waily, why does nobody make hardware that Just Works™ anymore, etc.) but ones I'm happy to live with for the convenience factor: I can take calls at work with the headphones already in my ears, so during the call I can easily consult my PDA, or have both hands free.

Philips SHE9600

I bought these headphones because I wanted in-ear headphones, Philips had been recommended to me on that basis, and they are built into a lanyard, minimising cable faff when combined with the S705. Sound quality is very good; they're generally comfortable (much better than I was expecting) but I wouldn't recommend in-ear headphones when the insides of your ears are sore or otherwise sensitive. I find that they block out just the right amount of external noise, the usual example being salesmen shouting into their phones, in that if the music is quiet or paused, I can tell what someone a few desks away, speaking normally, is saying if I concentrate. The length of the lanyard is just about acceptable for use with a device containing a microphone, such as the S705; I can always hold the device closer to my mouth with one hand if I'm having trouble being heard.
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