Return-Path: Subject: Re: [Bluez-devel] sco link help needed From: Marcel Holtmann To: James Courtier-Dutton Cc: Fred =?ISO-8859-1?Q?Sch=E4ttgen?= , BlueZ Mailing List , Simon Vogl In-Reply-To: <403916CB.3060205@superbug.demon.co.uk> References: <4034CA08.50500@soft.uni-linz.ac.at> <200402191629.38846.bluez-devel@schaettgen.de> <40376D2B.1060904@superbug.demon.co.uk> <1077452836.2716.42.camel@pegasus> <403916CB.3060205@superbug.demon.co.uk> Content-Type: text/plain Message-Id: <1077485446.2832.14.camel@pegasus> Mime-Version: 1.0 Sender: bluez-devel-admin@lists.sourceforge.net Errors-To: bluez-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: List-Post: List-Help: List-Subscribe: , List-Archive: Date: Sun, 22 Feb 2004 22:30:47 +0100 Hi James, > A agree that we need a clearly defined interface for the bluetooth SCO. > For SCO connections the interface will HAVE to be a callback based > interface. SCO is all about realtime data, and we must ensure minimal > latency, so that requires a callback interface. > I.E. We set up the SCO connection, and get it to callback after every X > frames received. The same for sending, callback saying I need X samples now! we already had this discussion and there is no need for such a callback stuff. If there is too much data, we simply have to drop some samples. > For alsa to work well with bluetooth, we will need some special handling > . The main use of alsa with bluetooth will be for headset communications > and therefore use the bluetooth headset profile. That is wrong. Also Handsfree, Cordless Telephony and Intercom needs a SCO to audio device mapping. With eSCO we will also have a data link and maybe more profiles in the future. > 1) Pairing. Provide a method to pair a bluetooth headset, so that if the > headset tried to open the connection. bluez will link to alsa only for > that paired device. So, we will need to be able to register alsa as a > pairing handler to bluez. Does the concept of a pairing handler even > exist yet in bluez? A headset will never set up the SCO channel. The AG does it. > 2) There is currently no method in alsa, for alsa to tell the > application "I am here now, listen to me!". So, if the headset initiates > the connection, there is currently no way to use alsa to inform the > application that the headset wishes to do such a thing. Maybe we could > implement this with an alsa mixer element that is present all the time > the pairing is present. And the application could poll the mixer > element, and if the mixer element changed state, we would open the PCM > to receive the audio. A sort of on/off hook indication. See above. And the userspace application must set up the audio device. Remember that we can't have a SCO link without an ACL link and this means that we need a control application which knows in detail when to create the audio device. > 3) The headset profile consists of a RFCOMM connection for setting > volume levels etc. and also a SCO connection for passing audio samples. > The alsa driver will implement the headset profile when working with > bluez. We might be able to expand that to the hands-free profile later. > The RFCOMM will therefore interface with the alsa mixer. the SCO > connection will interface with the alsa PCM. No. The Bluetooth ALSA driver is not in any way related to a profile. > 1) The alsa driver for bluetooth will be a kernel mode implementation of > the bluetooth headset profile. No profile implementation in the kernel. It is userspace stuff. > 2) A userspace tool will be used to configure the bluetooth pairing and > configure the alsa-bluez link. This has nothing to do with it. Pairing is independent from an ALSA driver. > 3) We will need to be able to implement bluetooth profiles in kernel > modules as well as user space applications. No. Profiles are userspace stuff. > 4) The bluez SCO interface should be changed to a callback interface. I don't see any need for it. Regards Marcel ------------------------------------------------------- SF.Net is sponsored by: Speed Start Your Linux Apps Now. Build and deploy apps & Web services for Linux with a free DVD software kit from IBM. Click Now! http://ads.osdn.com/?ad_id=1356&alloc_id=3438&op=click _______________________________________________ Bluez-devel mailing list Bluez-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bluez-devel