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Subject: Re: Unlocking the full features of the MAS chip (long, sorry)
From: Brent Geery (fasttimes_at_mochamail.com)
Date: 2003-04-29


On Tue, 29 Apr 2003 01:18:41 +0200, Linus Nielsen Feltzing
<linus_at_haxx.se> wrote:

> Brent Geery wrote:
> > After taking another look at the MAS datasheet, I've noted several
> > features that have not yet been implemented as user configurable
> > options.
>
> Maybe I'm just old and cranky, but I don't take this kind of "why
> haven't you done all this yet" comment all too well. My available time
> for this project is limited. I have worked hard to get the recording
> stable before adding detailed features. I have intended to add moe
> control over the recordings, I just haven't come to that yet.

No, you're just getting old an cranky, and maybe a bit paranoid. ;)
All I said was, well... what I wrote. I read the datasheet and
noticed some neat capabilities that haven't yet been implemented, and
I wrote to ask if they were missing because of a limitation of the
Archos' implementation of the MAS chip, no interest, or they just
haven't been addressed yet.

Before I posted a message, I took the time to read every single
message of the list archives (all 10,000+.) I try to keep my
suggestions to things that can be accomplished, and (hopefully,) on
the simple end of the programming scale.

I understand the hard work that has gone into producing Rockbox, and
very much appreciate it (really.) I tried to learn programming four
times (C++) but I just can't seem to get the hang of it. Same for me,
trying to learn a second language. You guys have my respect for your
abilities.

In short, don't confuse my enthusiasm, for impatience, or being
unappreciative.

> > Add ability to disable/enable CRC protection -
>
> Please explain to me what you intend to gain by not using the CRC. Two
> extra bytes for data? Sure, we can add a CRC option, I just didn't think
> anyone would mind it being enabled.

Some (older only?) hardware players have had problems playing MP3s
with CRCs. Many players (soft and hard) just ignore CRC anyway.

> > Add ability to switch between MS and Intensity Stereo encoding modes
>
> Sure. If you want lower quality, go ahead and file a request.

OK, I'll file it.

> > Is timecode insertion enabled or disabled? -
>
> Of course the timecode is disabled. Do you really want an option for that?

No, I was just asking *how* it's configured in Rockbox. The timecode
is basically useless.

> > BTW, the Bit Reservoir setting (the "independent frames" setting in
> > the menus) isn't held through a power cycle.
>
> A bug indeed. This is fixed now.

Thanks!

> > Also, isn't the built-in mic mono? In this case, selecting mic as
> > the audio source, should always enable mono recording, regardless of
> > the user setting. Why lower the quality with stereo encoding?!
>
> Earlier in this letter you wanted more options, now you want less.
> Explanation: It was easier writing the recording code when all options
> were selectable regardless of source. But sure, mono is the best choice
> for mic recordings.

Well, options that have a reason or purpose. Now that I think about
it more, I've read of some hardware players that have problems playing
mono files (play double speed, ect.), so there might be a valid reason
for wanting to encode the mono mic in stereo mode. But, that's about
the only logical reason for wanting to do that, I can see.

> > Oh, one other thing. I think I remember this being reported already,
> > but I thought I mention it again, just to be complete.-- I notice
> > that if you set the mic gain all the way down to 21.1 dB, you get no
> > sound!
>
> Yes, that's the way the MAS works. Don't ask me why.

Strange! Is there any reason then for allowing the setting? I
suppose it is currently acting as a sort of mic mute control.

> > Ok, that is for the recording features. I also noted lots of
> > playback features missing/limited so far.:
>
> Sure, sure, sure.
>
> And other people complain that there are too many options/settings.

To a gadget freak, there's never too many options, knobs, buttons, or
adjustments. :) If I can ever find that darn 8MB memory chip, I'll
be doing that upgrade as well.
 
> > Increase setting precision of Bass/Treble/Loudness controls -
> > 1/8 dB (.125 dB) steps can be done for Bass and Treble,
> > and 1/4 dB (.25 dB) for Loudness.
>
> If I add better precision for this, other people will complain about
> them being too fine.

The traditional way of dealing with that situation, is having two
speed steps. Hold the button down, and it steps in (the current) 1dB
increments. Click the button, and it steps in the finer resolution.
Everyone happy. This applies to any control with a wide settings
range.

> > Expand balance control to full dB range - Could we have the balance
> > controls expanded out to the full +/-127 dB range that the MAS can do
> > (1 db steps)? How about calibrating to dB's,
>
> Maybe I haven't used that much audio equipment, but I haven't seen any
> device so far with a balance control with dB as a unit. Do you feel that
> the balance control is inadequate?

My Kenwood receiver, for example, has balance calibrated to dB. It is
uncommon on consumer potables, but not home gear or pro stuff.

Regardless the scale used, a more precise settings would be helpful.
My left ear has some damage, so I really do use the balance control to
compensate. In the current config, I would need a setting somewhere
about 1/3 between 10% and 20% to get the stereo image correctly
centered.

> > Add the 20ms setting to Automatic Volume Correction control -
>
> Yes, we have left that option out, since it is useless for music
> listening. We reset the volume for every track change anyway.

I thought 20ms might have some use when playing back speech based
tracks.

> > Add full user control of Dynamic Bass controls! - Currently, we can
> > only adjust Strength, leaving the settings for Harmonics, Center
> > Frequency, or Shape out of our ability to change. It would be nice to
> > be able to "tune" Dynamic Base to fit our own particular headphones.
>
> This is planned.

Yeah! Very happy to hear that.

-- 
BRENT - The Usenet typo king. :)

Fast Times At Ridgemont High Info http://www.FastTimesAtRidgemontHigh.org Voted #87 - American Film Institute's Top 100 Funniest American Films



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