[mythtv] No per-individual line-level adjust: bug or missing feature?

Daniel Kristjansson danielk at cuymedia.net
Sun Jan 15 15:16:56 UTC 2006

On Sat, 2006-01-14 at 22:45 -0500, f-myth-users at media.mit.edu wrote:
> Should I open a ticket on this [*], or will it be closed as "feature
> request without attached patch"?
It will be closed...

>   If I hear nothing (or encouragement),
> I'll do the former; if I hear the latter, I'll add it to the wishlist
> at the new wiki.
Right place.

> In short, it seems buggy to me that Myth assumes that all capture
> cards will agree on their audio level when capturing.  Apparently
This doesn't seem like a big problem on my machines. There is a slight
difference between the PVR-500 & PVR-250, but at a few dB it is hardly

> My suggestion is to put a per-card slider into mythtv-setup's screen
> for each capture card (where this is supported by the card; some might
> not).  This slider is used in addition to the master capture slider set
> in whichever recording profile is active.  [And see [+] for a further
> suggestion.]  The value should get stored in some appropriate table, 
> consulted when a capture commences, and be multiplied together with
> the master capture mixer when initing the card.  (A more user-friendly
> approach would be to be able to adjust this in real time, instead of
> via repeated trips to mythtv-setup, but that seems like a lot more work.)
> Presumably the slider should be an attenuator, like the rest of them
> in the UI, so 100% is unity & everything else is quieter, and should
> default to 100%.
Sounds like a good idea, it could be adjusted while recording just like
the recording picture attributes 'G'. I don't think 100% should be the
default though, you tend to get clipping if you go above 70% on any amp.

> split setups where the STB drives something else as well); and also
> that some individual channels run -very- hot---my own cable feed has
> mismatches of ~9dB across certain channels I watch, and this mismatch
> has been consistent across -years-.  If I could stop constantly
They are probably just using range compression on the loud station, this
is a technique used by pop bands and advertisers to sound louder without
actually increasing the peak volume (what you set with the volume knob.)
I'd love to have an audio filter that detected restricted range in the
audio and undid the damage as best it could (and reduced the loudness).
But using the volume control on these loud stations would work...

-- Daniel

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