Re: [Advocate Play Ogg] Two thoughts: automated conversion, and radio4all.net.

[Pandu E Poluan]

Unfortunately, no. One have to listen to an *audio* track to determine if it sucks or not.

You can have some prominent warning though, to the tune of:

" Converting from MP3 to a lower-bitrate Ogg Vorbis *might* degrade your audio track. Conversion between lossy formats, even to a higher-bitrate one, *will*not* increase the quality of your audio track. If your MP3 track sucks to begin with, then the Ogg Vorbis track will also suck. "

Some guidelines for conversion:

1. Refrain from going down more than 2 levels of quality. 

http://wiki.hydrogenaudio.org/index.php?title=Recommended_Ogg_Vorbis
 provides a table relating Vorbis' level of quality ( -q ) to approximate bitrate.

For example, if the source MP3 is encoded at 128 kbps (CBR or averaged VBR), that corresponds to Ogg Vorbis -q 4. Do not go lower than -q 2.

2. Stay away from the negative levels of quality.

-q levels lower than 0 *will* sound sucky if played in a PC. On PDAs, played in a noisy environment (e.g. in a bus, on a park/road), -q -1 may sound acceptable.

A final thought: Why web-based conversion? Good MP3 files are multi-megabytes in size, and so will the Ogg Vorbis file. Better to use freely (gratis) available converters.

{p}

On 5/29/07, Karl Fogel <address@hidden> wrote:

"Pandu E Poluan" <address@hidden> writes:
> Transcoding from one lossy format onto another will always degrade
> quality. See http://wiki.hydrogenaudio.org/index.php?title=Transcoding
> for a description and illustration.
>
> Assuming that the original MP3 is good (e.g. encoded using LAME),
> transcoding to a similar bitrate or slightly-lower bitrate should not
> degrade too much; that's my experience transcoding from 128 kbps MP3's
> to ~128 kbps (approx) Ogg Vorbis, or even to ~96 kbps (approx) Ogg
> Vorbis.
>
> Problem is if you have a sucky MP3, transcode to a too-low Ogg
> Vorbis... then people will complain that Ogg Vorbis destroys their
> song.

Can such suckiness be detected automatically?  Then the site could
refuse to do the conversion, or at least warn the user...

-Karl

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