[MPlayer-dev-eng] [PATCH] remove limits from af_equalizer

[Corey Hickey]

Reynaldo H. Verdejo Pinochet wrote:
>>It's not really a high priority of mine -- I just noticed that it could
>>be done and probably should. Here are the reasons:
>>
>>* It's possible to pass af_equalizer one or more suboptions of 12 that
>>causes it to clip with audio that is loud but still of fairly "usual"
>>volume. So, a maximum of 12 doesn't necessarily protect users from
>>themselves.
>>
>>* Conversely, values higher than 12 may not cause clipping with quieter
>>audio. In this case, 12 is an artificial restriction.
>>
>>* af_volume is an easy way to enforce clipping if necessary and can use
>>soft clipping, which may be desirable.
> 
> 
> All this leaves me the impresion youre measuring efectivity/usability
> of the filter by means of his ability to *clip* rather than his hability 
> to correctly filter/boost a given freq range.

Actually, af_equalizer doesn't clip on it's own. By the time I wrote my
last email I had gotten mixed up and thought it had. What I should have
said instead of "cause clipping" is "cause out-of-range values to be
sent to the sound card". Sorry about that.

To restate my point, I'll say that af_equalizer already is capable of
generating out-of-range values, so the current limits are not effective.
Moreover, those limits can be too restrictive with audio that is fairly
quiet.

> AFAIK eq filters are used mainly to work over a given dynamic range
> using cutoff freqs to (among other things) *avoid* clipping

I actually know very little about traditional audio equipment -- I'm
just approaching this from the standpoint of making the filter more
flexible.

>>* Suboptions with values much lower than 12 have hardly any effect.
>>While they aren't really useful, there's no danger in allowing them.
> 
> may a wider bost range be enough? not that Im against leaving it unrestricted
> but I wanna be sure why ;) especially on changes that can lead users
> to wrong / bad results.

Probably a wider range would be fine, but I consider it unnecessary. Any
value chosen would be arbitrary, and any value high enough to avoid
restricting the amplification of a quiet source would be high enough to
be damaging to a loud source.

The current limits encompass most of the useful values, and I noted that
in my patch to the man page. I've attached a new patch that describes
more accurately what happens with suboption values that are too high.

-Corey
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