Avoid vorbis -quality below 0.250 ?

[ookzDVD]

I just noticed last night that after encoding vorbis
at quality 0.001 'til 0.200 I still got the "noise" effect,
but after I try the quality 0.250 the "noise" effect is gone.

It was from the "Insomnia" and "Murder by Numbers" .ac3 files,
use the BeSweet 1.4 & 1.5b2 and OggMachine 0.5 and 0.61 with
surround2 mode, Post Gain and Hybrid Gain, all the same result, "noise" effect at the quality below 0.250.

Anyone experience that problem ?

[JohnMK]

Everyone hears differently and by definition has different sensitivies. This is a very subjective assessment, but I personally never go below .200 unless the movie is extraordinarily noncompressible and I absolutely MUST have 1 CD. So far, that's only happened once.

I should add that IMO, .200 is easily approaching transparent to my ears for the kind of setting I'm in when I usually watch these encodes. .000 is radically less transparent. For only about 25kbit/s more, the added bitrate seems to really push the sound quality over that threshold for me, so it's almost never ever worth it to use .100 or .000, for my ears, and I suspect this holds true for most people, as my ears are pretty 'average.' So what's the price, 25kbit/s taken from video, added to audio? What's the quality difference? +40% for the audio, -2% for the video. So my position really does stand up to mathematical scrutiny, too . . . :)

[ookzDVD]

@JohnMK,

Sure, I will not go below the 0.250 again since last night :)
and since the XviD's B-Frame is in the state of stable and it
surely save more space for the audio.

[RadicalEd]

Generally when needed .200 is okay for me, but the sweet spot for vorbis really does seem to be 96 kbps/q.250

[JohnMK]

I would generally agree. I never go above -q3/.300 anymore, even for musicals (Amadeus, Sound Of Music, Moulin Rouge, etc.) and especially compressible movies (Panic Room, Evil Dead, etc). .300 is very, very good. It's certainly the equal, to my ears, of 160kbit/s mp3. There's just no point in going above .300 for most people, but yes, if you have particularly good hearing (most people do not), and you watch your own material, then I suppose maybe you need .300 as a minimum and .400 as typical. Part of the reason ogg vorbis does so remarkably well at these low bitrates is because of its amazingly low stereo overhead. Mp3 uses a very bit-intensive method of keeping the stereo field, whereas ogg vorbis uses point stereo, a far more bitrate efficient method. At higher bitrates, it uses a less aggressive form of point stereo that preserves the stereo field almost perfectly, and at even higher bitrates (-q6 + I believe) it turns off point stereo completely, but at low bitrates, such as -q0 to -q3, there will be a small but noticeable reduction in stereo field separation.

[Sven Bent]

i woulde never go below -q4 (~128kbits) unless it was for series as it mostly contains voice. I use -q3 (~96kbits) for that