[mythtv] [mythtv-commits] Ticket #5900: AO: Generalise upmix and AC-3 encoding

John P Poet jppoet at gmail.com
Mon Nov 10 02:14:16 UTC 2008

On Sun, Nov 9, 2008 at 6:23 PM, foo bar <foobum at gmail.com> wrote:
> 2008/11/10 John P Poet <jppoet at gmail.com>
>> >  * Turn on resampler where sr != 48k ![1] [[BR]]
>> This is optional, right?!?!
>> I paid extra money for a soundcard that actually does 44.1KHz
>> correctly, so I could have "bit perfect" audio.
> At the moment it's not because recent versions of ALSA resample to 48k by
> default anyway.
> The SRC we use is *much* nicer than the linear interpolation that ALSA
> inflicts.
> Besides, many cards don't do 44.1k - ideally we'd know what the card
> supports before we open it,
> but it's a bit messy to implement and the SRC gives a SNR of 97dB at 97% bw
> anyway. I really didn't
> want to add any additional config, but happy to consider another way of
> doing it..

Modern ALSA will automatically resample to 48, but only for cards that
need it.  Mine does not.

How are you defining SNR?  There is no way you can resample a 44.1KHz
source into 48KHz and have it be "accurate".  To my ears, resampling
like that always results in a least some sibilance and tends to muddy
the hight frequencies.

Assuming this gets committed to myth trunk "as is", I hope you can
provide me with a patch to disable that "feature" .  I already compile
myth with my own patches added on, so that is not a problem for me.


A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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