From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Losi Subject: Re: Event Based time synchronization with ALSA Date: Tue, 18 Jan 2005 12:47:11 +0100 Message-ID: <41ECF73F.7070404@hypersonic.it> References: <41EB9874.4060407@hypersonic.it> <41EBEB8F.9030009@gardena.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <41EBEB8F.9030009@gardena.net> Sender: alsa-devel-admin@lists.sourceforge.net Errors-To: alsa-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: Benno Senoner Cc: alsa-devel@lists.sf.net List-Id: alsa-devel@alsa-project.org Hi Benno, thank you very much for you response. Benno Senoner wrote: > The above routine has the advantage that you can use any kind of > periodsize (fragment size) in ALSA > and the send_rtp packet() always gets 20msec worth of data. > But you must ensure that the ALSA period size must be <20msec , > otherwise too much jitter is introduced. I see your point.... but I would have two objections: - I don't want/can't use threads - I get too much jitter If I make poll timeout every 20ms in the main loop, I'm sure I get 20ms worth of data so I can busy loop to reading (in blocking mode) all samples (If I would want to enforced that period is power of two, I could choose the max power of two number of samples that is divider of the required number of samples) That would be 8000HZ sampling for 20ms => 160 sample per packet => 5 32samples reads But I'd rather tell ALSA: "please wake up poll as soon as you have 160 samples available". Is that feaseble? Can I expect to be always woken up? How snd_pcm_sw_params_set_avail_min snd_pcm_sw_params_set_sleep_min snd_pcm_sw_params_set_start_threshold relates to my problem? I tried to read the API doc but, since I've no experience with audio programming, I didn't get all the points... Can anyone point to a good poll based read example? thanks again benno! Paolo ------------------------------------------------------- The SF.Net email is sponsored by: Beat the post-holiday blues Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt