Return-Path: Message-ID: <455CCAF4.8020007@silicom.fr> Date: Thu, 16 Nov 2006 21:32:52 +0100 From: Fabien Chevalier MIME-Version: 1.0 To: BlueZ development Content-Type: multipart/mixed; boundary="------------050409040509070603080106" Subject: [Bluez-devel] SCO on bluez : some architectural tips Reply-To: BlueZ development List-Id: BlueZ development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: bluez-devel-bounces@lists.sourceforge.net Errors-To: bluez-devel-bounces@lists.sourceforge.net This is a multi-part message in MIME format. --------------050409040509070603080106 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Marcel & Brad, I send you this e-mail to share some of the experience acquired while writing bluez-headset. There is much to share but i'll do it bits at a time, it will be more easy to digest than a 300 lines e-mail :-). So let's talk about SCO today. :-) SCO is designed for low quality (poor Hz rate). It's only application is telephony. However it requires *really* low latency. At first hand i tried the same approach as you did, which means route audio trough a daemon that could do all kind a of funny and interesting stuff in it. This would have been a very interesting approach. However result was really bad, for two reasons: * The unix socket between application and the daemon would queue some data, which would add unwanted delay. * And moreover, the fact to send the data trough a 3rd party unix process (the daemon), resulted in jitter due to scheduling behaviour. Do avoid hearing audio cuts in the headset, i had to add run daemon as root and decrease its nice value to unsane levels. Due to this, i had to fall back on having the SCO file descriptor available in application process space. However, due to the fact a2dp is not supposed to be used for delay sensitive streams, it is possible to use this architecture for a2dp. :-) Cheers, Fabien --------------050409040509070603080106 Content-Type: text/x-vcard; charset=utf-8; name="fchevalier.vcf" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="fchevalier.vcf" begin:vcard fn:Fabien CHEVALIER n:CHEVALIER;Fabien org:SILICOM adr:;;4 rue de Jouanet;RENNES ATALANTE;;35700;FRANCE email;internet:fchevalier@silicom.fr title:Software & Studies Engineer tel;work:+33 (0) 2 99 84 17 17 version:2.1 end:vcard --------------050409040509070603080106 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV --------------050409040509070603080106 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Bluez-devel mailing list Bluez-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bluez-devel --------------050409040509070603080106--