Thank to you and your friend for this explanation; very useful. Amie
-----Original Message----- From: pc-audio-boun...@pc-audio.org [mailto:pc-audio-boun...@pc-audio.org] On Behalf Of Dane Trethowan Sent: 26 December 2009 22:05 To: PC Audio Discussion List Subject: Re: Pros and cons of varible bit rate Okay, I just consulted an audio engineer abut what you wrote about minimum bit rates for VBR encoding and here's his response, it also talks about setting VBR quality and I'll have a few words to say about this after his quotation which follows: > Well, basically it depends on what you're trying to do. There are several factors that contribute to VBR quality (apart from encoding quality settings of course). Most immediately noticeable is the over-all VBR quality setting, which `weights' the VBR result between the minimum and maximum you set. Imagine VBR as a set of scales swinging everywhere between min. and max. depending on what's going into the encode. VBR quality simply determines how the scales are weighted, either more towards minimum or maximum depending on what you set. The higher VBR Quality, the less the encoder will `throw away', and so the more it will weight the encode towards the higher end of the scale. If the quality is set high enough, you won't achieve *anything* by increasing the minimum; all you'll do is make your file larger for no benefit, since the encoder will waste a load of bandwidth encoding things (such as silence or low frequencies) that don't need it. Conversely, if your VBR Quality setting is too low, the encoder will throw away so much that everything will get pushed towards the lower end, and so the Minimum setting will make a great deal more difference. But even then, all it will do is make your file bigger, and probably it won't help the encode quality, since you shouldn't have set the quality so low in the first place. > > So, basically, for normal operation, it's a complete waste of time pushing up the minimum. The exception is if you have a hardware player that can't cope with very low bitrates (our Omni DVD players were hopeless with anything below 64KbPS), unless, _perhaps_ if the source is *very* noisy (an old dodgy cassette) where you don't want noise causing a load of artifacts, but you still want the file as small as possible. But under those circumstances, you'd be far better off processing the original source and removing as much noise as possible without damaging the audio _before_ encoding. > > The only other reason you might want to push up the minimum is if the encoder has a dodgy VBR algorithm that tends to push too much towards the bottom of the scale, even when the VBR Quality setting is high. LAME's `--vbr-old' algorithm is excellent, but `--vbr-New' still has problems. Unfortunately, other encoders (such as Fraunhofer) are a *hell* of a lot worse, so if you're forced to use them, it might be worth it. > > Anyway, hope this explains things; basically, unless you have a very specific need, don't play with Min/Max bitrates - you're likely only to get worse encodes and bigger files. Thank you kind Sir for your time and trouble <smile> so now to my additional notation about VBR quality and this can add to confusion. When setting VBR quality it works in the reverse as it looks, in other words the lower the number the higher the VBR quality, 3 or 4 may be a good setting for music, for mono audio or talking books, audio documentaries etc try say between 4 and 6. On 27/12/2009, at 6:38 AM, Kevin Lloyd wrote: > The only point I'd add to Dane's notes is that I have read advice around not setting your variable floor too low. I'd suggest for music that you set the floor to 128kbps rather than the suggestion below of 16kbps. > > Regards. > > Kevin > E-mail: kevin.llo...@sky.com > ----- Original Message ----- From: "Dane Trethowan" <grtd...@internode.on.net> > To: "PC Audio Discussion List" <pc-audio@pc-audio.org> > Sent: Saturday, December 26, 2009 7:33 PM > Subject: Re: Pros and cons of varible bit rate > > >> I suppose it comes down once again to personal preference, I've been using varriable bit rates for youears. >> >> As I understand it, encoding with a varriable bit rate takes a lot longer as the encoder looks at every sample of the song thus deciding what bit rate it should be encoded at, silence for example is encoded at a lower bit rate than a full sample of orchestra sound, minimum and maximum bit rates for variable encoding are set up with your encoding engine such as LAME so for the best and accurate results you're better off doing this sort of thing manually with a command line so use an app which supports this, Exact Audio Copy is an excellent choice here. >> >> Their are several methods of VBR encoding, "Old" and "new", "new" is quicker for those jobs you want out the door fast but quality isn't quite as good if you're picky, with today's flying processor speeds you may as well use "Old". >> >> Also note that some older players may not handle VBR playback though I haven't struck one that doesn't yet. >> >> Suggested minimum and maximum bit rates for VBR? Well just use the minimum and maximum rates available or if you're configuring from a command line or a piece of software that takes full advantage of the LAME-ENC.dll library then 16 bits for the minimum and 320KBPS for the maximum, there are 2 quality settings you have to be aware of here, one is VBR quality and you may wish to change this for certain audio material you're encoding, say music and talking books. The other quality setting leave at maximum, will take longer but far better results. >> >> >> On 27/12/2009, at 6:21 AM, Jamie Pauls wrote: >> >>> The subject is a question, not a statement. I have been uploading Main Menu archives as a 128KBPS MP3 file. I see that many people recommend 192KBPS, but there a parts of the show that really don't need that high a bit rate. In fact, I have also read that encoding at too high a bit rate can cause unwanted artifacts just as much as encoding at too low a bit rate. Variable bit rate seems a good choice for me to use, but I would like some thoughts from audio experts. Thanks. >>> >>> >>> Jamie Pauls >>> MSN: jamiepa...@hotmail.com >>> Skype: jamie.pauls >>> >>> To unsubscribe from this list, send a blank email to: >>> pc-audio-unsubscr...@pc-audio.org >> >> >> ****************************** >> >> Dane Trethowan >>> From Melton Victoria Australia >> mailto:"grtd...@internode.on.net >> Twitter: http://twitter.com/grtdane >> blog: http://www.grtdane.wordpress.com >> Phone United Kingdom >> 02032874641 >> Phone Australia >> 0390058589 >> Phone United States >> 8159261869 >> Fax: >> +61 3 9743 7954x >> MSN grtd...@dane-trethowan.net >> skype:grtdane12 >> >> ****************************** >> >> >> >> >> >> To unsubscribe from this list, send a blank email to: >> pc-audio-unsubscr...@pc-audio.org > > > To unsubscribe from this list, send a blank email to: > pc-audio-unsubscr...@pc-audio.org ****************************** Dane Trethowan >From Melton Victoria Australia mailto:"grtd...@internode.on.net Twitter: http://twitter.com/grtdane blog: http://www.grtdane.wordpress.com Phone United Kingdom 02032874641 Phone Australia 0390058589 Phone United States 8159261869 Fax: +61 3 9743 7954x MSN grtd...@dane-trethowan.net skype:grtdane12 ****************************** To unsubscribe from this list, send a blank email to: pc-audio-unsubscr...@pc-audio.org No virus found in this incoming message. 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