>From the CDEX manual...worth a read I think...
Settings for Lame MP3/Blade DLL/Internal MP3 encoder:
This paragraph describes the options for the encoder mentioned above.
However, not all options might be available for certain encoders.
Bitrate (default value 128 Kbits/s):
Determines the number of bits per second.
Mode (default value Stereo):
With the LAME encoder, you can specify how the file is encoded. The default
stereo option is recommended, but at lower bit-rates, the Joint-stereo or
Forced stereo can yield better sound quality.
Stereo: In this mode, the encoder makes no use of potential similarity
between the two input channels. It can, however, negotiate the bit demand
between both channels, i.e. give one channel more bits if the other contains
silence.
Joint stereo: In this mode, the encoder will make use of a correlation
between both channels. The signal will be matrixed into a sum ("mid") and
difference ("side") signal. For quasi-mono signals, this will give a
significant gain in encoding quality. This mode does not destroy phase
information like IS stereo that may be used by other encoders. This setting
can be used to encode DOLBY ProLogic surround signals.
force joint stereo: This mode will force MS joint stereo on all frames.
It's faster and it uses some special mid and side masking threshold.
Mono: This option will forcibly generate a mono file; if the input file is
a stereo file, the input stream will be read as a mono by averaging the left
and right channels.
Quality (default value Normal):
With the LAME encoder, you can specify the output quality; thus you can
trade off encoding time against sound quality. The default (normal) is
recommended for the lower bitrates (<160 kbps), high quality for bitrates
>160 kbps. The voice quality is more or less optimized to generate the best
quality for voice. Details of the R3Mix quality option can be found at
http://www.r3mix.net.
MPEG-I/II setting (default value MPEG-I):
The difference between MPEG-I and MPEG-II are the sample frequencies of the
input file. MPEG-I can handle input streams (WAV files) with a sample
frequency of 48000, 44100 and 32000 Hz. MPEG-II on the other hand will
support stream for 24000, 22050 160000 Hz. Basically, use MPEG-II when you
want to encode with low bit rates (e.g. for voice files, or if you need
small MP3 files with reduced quality). As you can see, the lowest bit-rate
for MPEG-II is 8 Kbits/sec while for MPEG-I the lowest bit rate is 32
Kbits/s.
VBR Method Setting
The VBR method setting allows you the change the VBR algorithm which is used
for the encoding (detailed information can be found in the LAME user
documentation - see http://www.sulaco.org/mp3/doc/html/index.html). The
following selections are available
Disabled: Don't use VBR; instead encodie with a Constant Bit Rate (CBR)
VBR-Default: Use the default VBR method (currently set to VBR-MTRH)
VBR-Old: LAME's first functional approach, based on masking, bisection in
the bit domain.
VBR-New: LAME's second approach, based on masking and direct noise
allocation.
VBR-MTRH: a combination of old and new (VBR) routines
VBR-ABR: The Average Bit Rate (ABR) setting, the encoding principle is
similar to what AAC uses as VBR encoding, it is based on perceptual
entropy, but more like CBR than VBR. When you select the ABR option in the
VBR Settings box, the ABR edit box will be enabled. In this edit box you
can specify the target average bit rate. Of course, a larger bit rate will
yield generally better-sounding (but larger) MP3 files.
ABR Settings
VBR Quality Setting
This option allows you to set the Variable bit-rate option. Variable
bit-rate encoding will enable dynamically determined bit-rates that depend
on the music content of the current frame. This improves the overall quality
of the encoded file without increasing the file size. This option sets the
criteria used to determine when to increase the bit-rate for a frame. The
lower the number, the lower the criteria will be. Thus VBR_0 will yield the
best quality (but the largest file size) while VBR_9 will have less sound
quality but the file size will be the smallest. The recommended variable
bit-rate option is VBR_4. If you don't want VBR encoding, set this option to
None.
Private
When enabled, it will set the private flag in the MP3 stream.
Original
When enabled, it will set the original flag in the MP3 stream.
Copyright
When enabled, it will set the copyright flag in the MP3 stream.
Checksum
When enabled, it will add a cyclic redundancy check (CRC) code in each
frame, allowing [the decoding software] to detect transmission errors that
could occur on the MP3 stream. However, it takes 16 bits per frame that
would otherwise be used for encoding, and therefore will slightly (probably
imperceptibly) reduce the sound quality.
E-mail: [EMAIL PROTECTED]
MSN: [EMAIL PROTECTED]
----- Original Message -----
From: "Dane Trethowan" <[EMAIL PROTECTED]>
To: "PC audio discussion list. " <[EMAIL PROTECTED]>
Sent: Thursday, September 02, 2004 8:00 AM
Subject: Re: VARIABLE BIT RATES WITH LAME, SOME NOTES
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Ok! well I have a comment to make on this subject.
>
> What you said below seems very general, I mean their are different things
> that people may want to encode, (music and speech for example) and (from
> what I understand) ABR will not work too well with music (VBR is supposed
> to work better) so you can see my concern when a manual for a product
> recommends one form of encoding over another in this way, if the manual
> actually provides some background information as to why the recommendation
> is made then fare enough.
>
> Secondly, without casting any doubts or making any criticisms towards
CDEX,
> I ask the question, just how old is the manual we're referring to. Its
> over 18 months since I've used CDEX and allot has changed in that period
of
> time with LAME, allot of work has gone into improving the whole LAME
> software so what the manual says about LAME may not be accurate any
longer,
> of course (me having not used CDEX for such a long time, I've lost touch
> and (for all I know) their may ahve been subsequent update releases of
CDEX
> too!).
>
> Now ABR and VBR, 2 very different systems. ABR works out the average bit
> rate of a file and encodes it that way where as VBR works on each frame of
> the file and encodes each frame to the best bit rate appropriate to that
> frame, if you have silence then encoding drops down to the minimum set (by
> default this is 32KBPS).
>
> The settings I spoke of in my original message were designed to get
maximum
> compression and quality using VBR, if the quality setting is either too
> high or too low you either end up with a small file of lousy quality or a
> massive file of good quAlity audio, people are under the impression that
> (with the VBR method) the higher the quality number the better the quality
> encoding so I was just making the point that the quality setting doesn't
> work as simply as that.
>
> 01:55 AM 2/09/2004 -0400, you wrote:
> >Hi all. I hear in the CDex manual that abr is maybe better than vbr.
If
> >you use variable bit rate, you should use the average bit rate, or abr.
> >----- Original Message ----- From: "Dane Trethowan"
> ><[EMAIL PROTECTED]>
> >To: <[EMAIL PROTECTED]>
> >Sent: Wednesday, September 01, 2004 7:18 AM
> >Subject: VARIABLE BIT RATES WITH LAME, SOME NOTES
> >
> >
> >>
> >>-----BEGIN PGP SIGNED MESSAGE-----
> >>Hash: SHA1
> >>
> >>Greetings!
> >>
> >>Sorry! I'm all over the place with e-mail at the moment.
> >>
> >>Some time ago, someone on list asked about VBR quality with LAME, they
said
> >>that they were getting mixed results with a quality figure of 9.
> >>
> >>This will indeed be the case as (with the VBR encoding) 9 is the worst
> >>quality you can use. The quality for VBR encoding is slightly different
to
> >>that of Constant bit rate encoding, the quality setting for VBR
> >>encoding affects both the encoded audio nad the size of the file thus
the
> >>best quality figure is probably about 5, where you get maximum quality
and
> >>maximum compression.
> >>
> >>LAME boasts 2 VBR methods, "OLD" and "NEW", "NEW", is very fast but
doesn't
> >>produce as good a results as does "OLD", which is considerably
> >>slower. Naturally! this situation will change as time goes on.
> >>
> >>-----BEGIN PGP SIGNATURE-----
> >>Version: PGP 8.0.3
> >>Comment: Dane Trethowan, a client of TFT-BBS run by Gordon Smith
> >>
> >>iQA/AwUBQTWv/SlBPqY64aUBEQKe9wCgzRz2ovd02UaAewsN5eY0A4cVmsgAoOU7
> >>P+lBFteSR0VToI4YkfrZz8ae
> >>=Dv1v
> >>-----END PGP SIGNATURE-----
> >>
> >>
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> >
> >
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> -----BEGIN PGP SIGNATURE-----
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> Comment: Dane Trethowan, a client of TFT-BBS run by Gordon Smith
>
> iQA/AwUBQTbFEilBPqY64aUBEQKnYgCg8m+1HlZOdMXrJg+wMYvn5qqO1zwAnjlq
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> =FJ8D
> -----END PGP SIGNATURE-----
>
>
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