[MPlayer-users] Audio sync issues with -udp-master/slave

jon jon at jonshouse.co.uk
Sun Feb 2 14:43:07 CET 2014

On Sun, 2014-02-02 at 10:14 +0100, Oliver Seitz wrote:
> > for a recent project I have to play three different audio files
> > synchronized to each other on three devices (each Raspberry Pi),
> > connected by wireless LAN.
> The udp-sync-feature is not meant to syncronize audio.
> The typical usage is a master which plays audio and video, and one or 
> more slaves wich play video only.
> Keeping sync on audio files is a whole different story than video. If a 
> video frame is 10 milliseconds early or late, noone will ever notice. If 
> audio samples are 10 *microseconds* early or late, that can make a real 
> noticeable difference. With audio, you cannot speed up or slow down the 
> playback speed unnoticed, and you also cannot drop or fill in extra 
> samples. All of that could be audible.
It *could* be but its not.....  

I program real time audio on embedded systems, I often have to double up
or drop a single sample to stay in sync, at 22Khz or better this is not
audible.   Dropping a sample (replacing it with 0) is audible as this
damages the average DC level of the audio and causes a click on the
amplifier, but doubling up (an extra identical sample inserted) or (with
slightly more care how its done) dropping a sample is not a problem.


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