Jim Lesurf wrote:
In article , DAB sounds worse
than FM wrote:
If you want to compare results with me then do the following:
Erm... what OS, etc, are you assuming I am using? :-)
* download Lame v3.90.3:
[snip]
You would need to direct me at a version that runs under RO on an
ARM-core CPU and which can be verified to act identically to the
one you use. However even if that were done and I had the time
to try it...
Okau, I'll just tell you the results I've had when I've done this in the
past. I recorded Radio 1 and Radio 3 off DTT and re-compressed
(transcoded) to VBR MP3 at a given quality and the classical music on R3
required a lower bit rate than R1.
Also, yesterday I encoded Morrissey's and Snow Patrol's most recent
albums, the latter because it's got quite a bit of the loud electric
guitars I mentioned, and the former because I've been playing about with
the new HE AAC codec recently and it suffers badly when starved of bits.
Both albums required a bit rate significantly higher than the norm for
that VBR quality setting.
It isn't clear to me what value the process you suggest would have
w.r.t the issues we were discussing in terms of the differences
between what the BBC do for R1/2 and R3.
If you had paid attention, I described a way of comparing difficulty of
encoding by comparing NMR (noise to mask ratio), and encoding using VBR
for a given quality setting will try to set the NMR to be relatively
constant -- MP3 encoders iteratively allocate bits to minimise the NMR
(or equivalently, maximise the mask to noise ratio).
If you wish to support your
argument for that then I'd assume you need to do so in terms of the
specifics of
the BBC signals and waveforms.
To prove this you don't need BBC signals or waveforms, you just have to
show that flatter spectra are more difficult to encode.
The snag being that to do so you
ideally may need access to the originals before they were level
compressed
and data reduced.
No, I wouldn't need access to the originals.
AIUI your point was based on argueing that the R1/R2 typical signals
have a more unform and flatter spectrum. My point was that it may
also depend on the number of spectral components, not just the
uniformity and range of those present.
A totally flat and very wide spectrum is bound to end up with more
frequency components post-masking than one that tails off far faster and
isn't as broad. It's an assumption, but a very, very good one. I'm sure
you've used far weaker assumptions before than the one I'm using.....
Without access to the BBC
original waveforms and their level compression, etc, how would
my attempting to use Lame establish this?
See above.
I'm going away for the weekend, so I won't be able to reply to any
further posts until I'm back.
--
Steve -
www.digitalradiotech.co.uk - Digital Radio News & Info
Find the cheapest Freeview, DAB & MP3 Player Prices:
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DAB R3 balance
Linear Mode
