Return-Path: Message-ID: <42B99440.3030501@xmission.com> From: Brad Midgley MIME-Version: 1.0 To: bluez-devel@lists.sourceforge.net Subject: Re: [Bluez-devel] Advanced Audio Distribution Profile (A2DP) References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Sender: bluez-devel-admin@lists.sourceforge.net Errors-To: bluez-devel-admin@lists.sourceforge.net Reply-To: bluez-devel@lists.sourceforge.net List-Unsubscribe: , List-Id: BlueZ development List-Post: List-Help: List-Subscribe: , List-Archive: Date: Wed, 22 Jun 2005 10:39:28 -0600 Victor, I am going to have a whack at adding fixed point tables and making the decoder optionally use fixed point. I will let you know. Brad Victor Shcherbatyuk wrote: > Hello all, > > Today I was playing with the timeout. None of the values I've tried > gives good results for HP headphones. Bigger values as I undestand lead > to a buffer underrun in the headphones (same sound as I get with fp > emulation on), while smaller values lead to frame(sample?) drops on the > headphone side (it kind of sounds faster, but I thing it just drops the > samples)? The only thing that is stable are breaks in the music I have > now and then. From another side, with Bluewalker, with the magic "87" it > sounds almost the same as with HP headphones (so still break now and > then), but if I reduce timeout by changing e.g. 87 -> 40 it becomes good > and there is no difference from the PC. That makes me think that there > is something to do with the buffering model used for these headphones. I > still want to chek it. > > The next step is the fixed point. As I understood Brad is already > looking in to it? Cause I also wanted to look into it somewhere in short > time... > > Regards, > Victor. > > -----Original Message----- > From: bluez-devel-admin@lists.sourceforge.net > [mailto:bluez-devel-admin@lists.sourceforge.net] On Behalf Of Brad > Midgley > Sent: Tuesday, June 21, 2005 20:03 PM > To: bluez-devel@lists.sourceforge.net > Subject: Re: [Bluez-devel] Advanced Audio Distribution Profile (A2DP) > > i was hoping to get the timing problem hammered by using setitimer. > unfortunately, there still seems to be some dependency on the cpu speed > which is surprising to me. there's a place in the code where the time > period reported by libsbc is multiplied by 87/100. that 87 has to be > tweaked for different cpus :( > > i came by the 87 by using my 1.4ghz pentium-M with the hp headset. > > the iphono and itech headsets are very forgiving with timing. they also > seem to have the worst problems with audio delay. > > >>>1) Is there anyone buse with sbc fixed point convertion? >> >>We need an integer only implementation of SBC. I may repeat myself, >>but I am not going to code this. This must be done by someone else. > > > i started trying to do this with a library (gnu mp). the library is > really meant for arbitrary-sized numbers, and not so great with short > floats. if i had a reference implementation of soft floating point in C, > i could dig into this again. i might try it without but i would have to > reinvent the normalizing floats after multiply/divides. > > >>>2) Is there anyone with similar problems (out-of-synch sound) and >>>knows how to solve it (or is it just about tuning the timer?)? > > > yes, we found out pretty soon that the hp headset insists on that "87" > to be tuned for different cpus. maybe there is something wrong with how > i did the timer or maybe itimer is not a great route to go. > > i also have an arm board that i am trying to use with this stuff. it can > *receive* audio if the encoder settings are turned way down but can't > transmit a2dp. see > > http://bluetooth-alsa.sourceforge.net/embed.html > > >>You need to encode the SBC frames in advance and then use a timer for >>sending them. I am working on a ALSA plugin that will do exactly this, > > >>but I think that won't help you on your embedded platform. > > > i'm very excited to see this part. go, Marcel! and hopefully you can let > us see what this work looks like soon :) > > Brad > > > ------------------------------------------------------- > SF.Net email is sponsored by: Discover Easy Linux Migration Strategies > from IBM. Find simple to follow Roadmaps, straightforward articles, > informative Webcasts and more! Get everything you need to get up to > speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click > _______________________________________________ > Bluez-devel mailing list > Bluez-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bluez-devel > > > This e-mail message contains information which is confidential and may be privileged. It is intended for use by the addressee only. 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