[mythtv] ReplayGain support for MythMusic
adeffs.mythtv at gmail.com
Tue Feb 26 18:35:15 UTC 2008
On Tue, Feb 26, 2008 at 11:54 AM, Chris Hamilton <chamilton at cs.dal.ca> wrote:
> > Just remember that some of us use S/PDIF and the soundcard's "volume"
> > doesn't actually do anything! (ie I'd much prefer it does it in
> > 'software' like most other apps do).
> Good point. So, the software approach is the only one, really. I
> should have a modified AudioOutputBase supporting software
> pre-amplification by the end of the week.
> > so Chris has it right in my mind (and how I use replygain). What is
> > being played should be looked at to determine the correct one to use.
> > I would say default to track gain "unless" a whole album is being
> > played which hopefully can be determined by looking at what the
> > playing play list contains and if it matches say >80% of the tracks in
> > that album as determined by the db. It would probably also be good to
> > have an override ability. A small icon displaying the current replay
> > gain status (a "T" or an "A" or blank) would probably also be helpful
> > and fairly non-intrusive.
> My thoughts on this was to do the following simple test:
> If the 'next' or 'previous' track (as defined by the current playlist
> ordering) belongs to the same album, then play the present song using
> the album gain if defined. Otherwise, use the track gain if defined.
the only thing I see wrong with this, and its something I don't do but
I've seen my friends do, is that they will put like 2 or 3 tracks from
an album on a playlist which would cause your test to use the album
gain as opposed to track gain which would be more appropriate. I'd say
if it were possible to do a % of total tracks check that it may work
better. Though checking whether shuffle mode is on may make this
scenario a moot point.
> Finally, a global setting might be useful, selecting between
> no replaygain / track gain only / album gain only / smart album gain
> > also, don't forget that replaygain *can* cause clipping if a gain
> > value is too great. I believe it will tell you both the suggested gain
> > to reach the target and the greatest gain that will not cause
> > clipping.
> > I'd highly suggest using the greatest non-clipping gain, or if made an
> > option using that as the default.
> While it doesn't explicitly tell you the maximum gain, most (all?)
> ReplayGain calculators also store peak information. From that, you can
> calculate the maximum possible gain before clipping will occur. So
> amplifying to a maximum gain before clipping occurs is reasonable.
> I've also got a few tracks that MP3 gain doesn't like for some reason,
> and has calculated ridiculous gains of like +53 dB. It might also be
> useful to have a configurable minimum and maximum gain.
> Finally, one last idea. The idea of ReplayGain is to make all tracks
> have the same perceived loudness. For some tracks, it may be that some
> amplification is needed, resulting in clipping if we truly amplify to 89
> dB SPL. Maybe we could have a configurable output level, and choose
> this such that *no* songs in the database will be clipped when amplified
> to this level?
well, unless we want to store two values a clipped and a non-clipped
value I think we should either just go with the non-clipping value or
somehow allow the user to decide. I personally would never want to
clip my tracks, but I can see how for a DJ a little clipping would not
be a big deal compared to a large change in perceived volume.
More information about the mythtv-dev