[vorbis-dev] Audo quality problem

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Simeon Maxein wrote:
>>It might be helpful if you could determin the lowest quality setting where
>>the problem (for you) goes away.  Say, within .5 or so.
> 
> It stops exactly at -q 6,00. At 5,99 it's still there, I can make it out
> without the slightest problem, and then at 6,00 I don't hear it any more.
> There is also a small "bitrate jump" from 5,99 to 6,00, so I guess the
> encoder changes some settings there. What is exactly happening there? I
> would be glad if someone could tell me.

At quality settings >= 6, stereo channel coupling becomes lossless (that 
means, the stereo picture is complete in q6+; the audio itself stays 
lossy, of course.) The problem you describe is well-known and occurs on 
a few selected pieces of music (not every song is affected noticably). 
There are many anecdotes about this, and the last time this was 
discussed, Monty acknowledged it and said something along the line of 
"thank you, we know of it, we have many examples but no hard data that 
show WHY this actually happens."

That was quite a while ago, and I believe I've heard that meanwhile the 
problem has been identified and will be fixed in Vorbis 1.1. However, 
please don't quote me on that, I am really not sure about it ... maybe 
someone else knows more details about the current development status of 
Vorbis.

You might also want to make sure that you're using Vorbis 1.0.1 - it has 
some quality improvements at low bitrates.

<p>Moritz
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