Return-Path: Message-ID: <404274D0.7040005@superbug.demon.co.uk> Date: Sun, 29 Feb 2004 23:25:04 +0000 From: James Courtier-Dutton MIME-Version: 1.0 To: Marcel Holtmann CC: BlueZ Mailing List Subject: Re: [Bluez-devel] SCO. Some ideas. References: <40421024.20602@superbug.demon.co.uk> <1078074126.1942.31.camel@pegasus> <40423226.8050007@superbug.demon.co.uk> <1078087109.1942.54.camel@pegasus> <4042575B.20305@superbug.demon.co.uk> <1078092105.1942.93.camel@pegasus> In-Reply-To: <1078092105.1942.93.camel@pegasus> Content-Type: text/plain; charset=us-ascii; format=flowed List-ID: Marcel Holtmann wrote: > Hi James, > >>Some audio applications need this "pointer" feature, which is why alsa >>provides it. >>An example of this is playback of DVDs. >>Video output needs to be kept closely in sync with the audio, and this >>"pointer" and "trigger" feature allow the application to closely control >>exactly when the sound plays. "trigger" handles the "start the sound >>exactly now", and "pointer" provides feedback, saying that "sound sample >>xyz is currently playing, so display video frame xyz now". "pointer" >>also provides for "audio is playing 0.25 seconds ahead of video, adjust >>it to match". >>These are not hardware specific features, all sound hardware has these >>features, including bluetooth audio, and we just need some way for >>higher layers to get access to the values. >>Another example is Voice over IP. If using a headset, one might want to >>use it to make VoIP calls over the internet. One of the most important >>issues with VoIP is latency. The lower the latency, the more natural the >>conversation will be. Long latency produces conversations will long >>breaks in between and possible delayed echos. It is a lot more difficult >>to have a natually smooth conversation if the latency is high. These >>"pointer" and "trigger" and "period_time_elapsed" functions allow for >>applications to program minimum latancy that any particular hardware can >>handle. > > > You shouldn't think so much about it. Try to implement the ALSA driver > without it and we see how it goes. > > Regards > > Marcel > So you want me to implement it in such a way that would add 10-20ms of latency and have no audio/video syncronisation features? We might as well stay with the current alsa over network sockets which is what we have now. Cheers James