Vorbis - Jul 2002 - Best quality setting for mp3 transcoded old radio shows

Hi,

I have a bunch of old radio programs (mystery/drama shows, not music) 
encoded at 32 kbit (and some 48kbit)  mp3 (mono).  I want to reencode 
them in ogg and make them available over gnutella.

My question is this.  What is the best quality level (-q) for 
transcoding them.  I want to preserve quality, but I want to be 
sensitive to the many modem based gnutella users.  I also want to to 
help introduce people to ogg in a positive way.  i.e. I want the best 
balance of size to quality for this use.  I am using mp32ogg, which by 
default uses quality 5 for these files which seems like overkill.  (It 
also adds a tag to identify the file as a transcoded mp3 to help 
preserve vorbis' reputation for quality.)

Thanks for any advice.

-Steve Bergman
steve@rueb.com

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Hi:

Well, MP3 files encoded that low are going to have some pretty serious
artifacts.  I've found that anything below -q 2 at rates other than
44.1khz
tend to produce significant pre-echo, though the original MP3 probably has
some of that too.  Honestly, you won't get a lot of improvement on file
size, if any, by transcoding that stuff.  I probably wouldn't bother if I
were you.  But if you're going to bother, encode and listen.

Geoff.

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On Mon, Jul 01, 2002 at 06:32:25PM -0500, Steve Bergman
wrote:
> Hi,
> 
> I have a bunch of old radio programs (mystery/drama shows, not music) 
> encoded at 32 kbit (and some 48kbit)  mp3 (mono).  I want to reencode 
> them in ogg and make them available over gnutella.
Keep in mind that these are likely mostly speech, and Vorbis is really
not designed for low-bitrate speech. A new codec, Speex (speex.sf.net)
is under development, which will be able to encode speech much
better. It is still in development, however, and end-user tools and
plugins are not yet available AFAIK, so I would not recommend sharing
files in that format yet.
> My question is this.  What is the best quality level (-q) for 
> transcoding them.  I want to preserve quality, but I want to be 
> sensitive to the many modem based gnutella users.  I also want to to 
> help introduce people to ogg in a positive way.  i.e. I want the best 
> balance of size to quality for this use.  I am using mp32ogg, which by 
> default uses quality 5 for these files which seems like overkill.  (It 
> also adds a tag to identify the file as a transcoded mp3 to help 
> preserve vorbis' reputation for quality.)
Of course we've all heard quite enough about why mp3->ogg is generally
a bad thing. Also, MP3 is presently more optimized for super-low
bitrates than Vorbis, but that will soon change (Vorbis already sounds
much better than MP3 at 64k). I suggest that you try to find some
processing method, with sox or some other sound-processing tool, that
can significantly improve the quality of the decoded MP3s. If you can
get something that sounds better all around than the original MP3,
more power to you, and encode the result to Ogg. Do note in the
comments, however, that it was transcoded from MP3 and
post-processed.

As far as quality, I'd agree that quality 5 is overkill for that sort
of source material (unless you get it to sound really good!). I'd go
with 2, but an extra .5 for good measure (so 2.5).

It's great that people like you have an interest in promoting Vorbis!


-- 
Kenneth Arnold <ken@arnoldnet.net>
- "Know thyself."


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Steve Bergman wrote:
> My question is this.  What is the best quality level (-q) for
> transcoding them.  I want to preserve quality, but I want to be
> sensitive to the many modem based gnutella users.  I also want to to
At those bitrates, MP3 has serious artifacts. Vorbis will try to
preserve them, waste a lot of bits on them and if you want the .ogg to
sound at least almost as "good" as the mp3, the .ogg will be bigger
than
the mp3. Don't reencode, just share those MP3s ... Vorbis RC3 can't make
good use of 22050 Hz samples anyways. This will plainly suck. If you
want to do this for the sake of sharing, find something that you can
directly encode to Vorbis, e.g. CD to .ogg.

<p>Moritz

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