[vorbis] Best quality setting for mp3 transcoded old radio shows

[Kenneth Arnold]

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 at arnoldnet.net>
- "Know thyself."


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