[pulseaudio-discuss] [PATCH 5/5] man: sync_volume parameters to manual page

[David Fries]

This is what I came up with, take it or leave it.

>  <section name="Default Sync Volume Settings">
>
    <p>
    With the flat volume feature enabled, the highest volume input
    stream sets the HW volume and lower volume streams are reduced in
    SW according to the current HW volume setting.  When the volume of
    the highest volume input stream changes all other streams SW
    volumes must be recalculated for the new HW volume.  The problem
    is sink implementations don't support requesting a HW volume
    change at a specific sample causing the resulting sound to
    momentarily be too loud or soft.  Sink implementations that
    support <What's the feature?  Querying the HW delay?> can be
    approximated and further refined with the following options.
>
>    <option>
>      <p><opt>enable-sync-volume=</opt> Enable sync volume for the sinks that
>      support it. This feature is enabled by default.</p>

As above, what determines if a sink supports enable-sync-volume or
not?

>    </option>
>    <option>
>      <p><opt>sync-volume-safety-margin-usec=</opt> The unit of time by which
>      the HW volume increases are delayed and HW volume decreases are advanced.
>      Defaults to 8000 usec.</p>
I wrote a paragraph on this one before I realized I was confused and
didn't get what it was saying, or what was safe or unsafe about this
value.  So how about,
The amount of time the HW volume increases are delayed and HW volume
decreases are advanced to avoid playing a stream too loud between the
HW volume change is in effect and SW volume samples are played.
>    </option>
>    <option>
>      <p><opt>sync-volume-extra-delay-usec=</opt> The unit of time all HW
>      volume changes are delayed. Negative values are also allowed.
>      Defaults to 0.</p>
>    </option>
How about "sync-volume-hw-delay-usec=" ?  Then,
The unit of time all HW volume changes are delayed if the volume
changes are a constant time early. Negative values are also allowed.

On Fri, Oct 15, 2010 at 10:22:16AM +0200, Paul Menzel wrote:
> I am still thinking that a ???normal??? users does not have a clue on how to
> determine to what value these options should be set. So it should be
> marked as expert value or something or a hint should be given on how one
> can determine what values should be used.

A program could measure the hardware mixer latency by playing a square
wave on one stream and adjusting the volume of another stream playing
silence.  Then adjust the parameters so that the wave doesn't vary as
the volume changes.  Too bad sound cards don't have the internal
analog loopback control anymore, now you would need to externally loop
the audio back.

-- 
David Fries <david at fries.net>
http://fries.net/~david/ (PGP encryption key available)