[pulseaudio-discuss] My attempt to reduce latency with pacat and tvtime

Steven Elliott selliott4 at austin.rr.com
Mon May 21 18:30:04 PDT 2012

On Mon, 2012-05-21 at 18:15 -0500, Pierre-Louis Bossart wrote:
> > 1) TVtime (that's what the original poster uses): doesn't handle audio
> > at all (but I was told that there is a fork that does), assumes that
> > there is a zero-latency analog wire coming from the TV tuner audio
> > output to the sound card's "TV" input. That's why the OP asks about
> > module-loopback and/or parec|pacat solution, as a replacement of the
> > said wire. Due to the now-invalid assumption about the wire, zero
> > latency is needed. Because the audio chain is external to tvtime,
> > there is no possibility for any A/V sync queries.
> Isn't the simplest solution to add a fixed delay for the video in 
> TVtime, and apply the same fixed delay in module-loopback? 

That's an interesting idea.  I suppose the audio frames would have to be
queued up and then rendered after the appropriate delay.  I'm not sure
if that would be simpler than my patch or not.  I'd have to know more
about how tvtime handles audio.

One concern is that tvtime has not had a release since 2005.  Also, are
there other programs that don't maintain A/V sync?  Perhaps it would
benefit them as well.

> Any attempts 
> to emulate the behavior of an zero-latency analog wire with PulseAudio 
> aren't very likely to succeed :-)

Fair enough.  My hope was just to keep it low enough.

|  Steven Elliott  |  http://selliott.org  |  selliott4 at austin.rr.com  |

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