Speex dev - Aug 2004 - Higher Bandwidth at lower quality settings

Hi Jean-Marc,
        I thought at quality 3 (wideband) - wb_submode1 that the 4-8k band was
not
using a codebook table.  From the code I can see that some sort of
"lsp"
encoding is performed.  What exactly does this encode?  (I assume lsp means
line-spectral pairs)
        The reason I am asking is I'm comparing the "effective"
spectral bandwidth
of Speex against the AMR-WB (G.722.2) codec.  (Available from 3GPP.org)
Speex performs very comparably to AMR-WB until the quality setting drops
below around quality 5.  At approximately equivalent bitrates AMR-WB
maintains the spectral bandwidth better, whereas Speex doesn't seeem to
match above 3.5kHz.  I was wondering if it would be possible to tweak Speex
to drop the narrowband quality at the expense of increasing the bandwidth?

Thanks,
Trevor

<p>-----Original Message-----
From: owner-speex-dev@xiph.org [mailto:owner-speex-dev@xiph.org]On
Behalf Of Jean-Marc Valin
Sent: Thursday, February 27, 2003 12:22 AM
To: speex
Cc: Trevor Yensen
Subject: Re: [speex-dev] Higher Bandwidth at lower quality settings

<p>> 	I was wondering if anyone has experimented with Speex's
wideband (16kHz)
> mode at lower quality settings.  In particular I have been using quality
3,
> and with wideband input files the resultant frequency spectrum is limited
to
> about an upper end around 3.5kHz (almost telephony quality bandwidth).
Has
> anyone tried increasing the spectral bandwidth at the expense of lowering
> the narrowband quality (ie using two very low bitrate codebooks, one for
> narrowband and one for the 4-8kHz band - to match the same bitrate at
> quality 3)? If you have can you comment on the quality?  (Looking through
> the Speex code, I noticed that at lower quality settings wideband mode
> basically reverts to narrowband.)
I'm really not sure what you mean. In wideband mode, both the low-band
(0-4 kHz) and the high-band (4-8 kHz) are encoded even at low bit-rates.
When encoding below a certain bit-rate, the high-band becomes a rough
approximation, but it's still there.

        Jean-Marc


--
Jean-Marc Valin, M.Sc.A.
LABORIUS (http://www.gel.usherb.ca/laborius)
Université de Sherbrooke, Québec, Canada

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Hi,
        I was wondering if anyone has experimented with Speex's wideband
(16kHz)
mode at lower quality settings.  In particular I have been using quality 3,
and with wideband input files the resultant frequency spectrum is limited to
about an upper end around 3.5kHz (almost telephony quality bandwidth).  Has
anyone tried increasing the spectral bandwidth at the expense of lowering
the narrowband quality (ie using two very low bitrate codebooks, one for
narrowband and one for the 4-8kHz band - to match the same bitrate at
quality 3)? If you have can you comment on the quality?  (Looking through
the Speex code, I noticed that at lower quality settings wideband mode
basically reverts to narrowband.)
        Anyway, this is an experiment I plan on trying, but I was wondering if
anyone had any tips.

Cheers,
Trevor

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> 	I was wondering if anyone has experimented with Speex's wideband
(16kHz)
> mode at lower quality settings.  In particular I have been using quality 3,
> and with wideband input files the resultant frequency spectrum is limited
to
> about an upper end around 3.5kHz (almost telephony quality bandwidth).  Has
> anyone tried increasing the spectral bandwidth at the expense of lowering
> the narrowband quality (ie using two very low bitrate codebooks, one for
> narrowband and one for the 4-8kHz band - to match the same bitrate at
> quality 3)? If you have can you comment on the quality?  (Looking through
> the Speex code, I noticed that at lower quality settings wideband mode
> basically reverts to narrowband.)
I'm really not sure what you mean. In wideband mode, both the low-band
(0-4 kHz) and the high-band (4-8 kHz) are encoded even at low bit-rates.
When encoding below a certain bit-rate, the high-band becomes a rough
approximation, but it's still there.

        Jean-Marc


-- 
Jean-Marc Valin, M.Sc.A.
LABORIUS (http://www.gel.usherb.ca/laborius)
Université de Sherbrooke, Québec, Canada

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Hi! I just stumbled onto your project (Speex) and it seems perfect for
archiving a radio show I record every night. The thing is, I would like to
encode in real-time, rather than having to record the wav and then use the
speex encoder to encode it. The radio show runs 5 hours, so a PCM wav would
be big to store first and then process with speex (not bad though, except 
the machine only has a 2GB harddrive).
Currently I am archiving my radio show using the Fraunhofer MP3 codec with 
some software
called AudioGrabber. I just have Audiograbber to record from the line-in on
my soundcard. I set it to use Fraunhofer to record directly as MP3 mono,
16kbps, 11kHz. I believe speex could produce better quality/smaller file
size. The problem I have is not being able to choose the speex codec in
Audiograbber instead of Fraunhofer MP3. Just wondering if there's a way to
make speex a selectable encoding codec. I'd like to use speex in real-time
to record/encode the radio show as it airs. Anything you could tell me
about this sort of functionality with speex would be appreciated. Thanks!

Ben

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