Newbie with VBR and ABR MP3's and choosing Bit Rates
Reply #10 – 2013-04-26 23:04:34
a) With your bitrate settings chance is very low that you are able to hear differences. That's why greynol asked for how you determined quality. b) The right way to check whether or not there is an audible difference to the original is by doing an ABX (blind listening) test. Probably the easiest way to do this is to use the ABX tool which comes with foobar2000. foobar is also a great tool for doing audio conversion and things like that, or to just listen to the music. c) Disabling bitreservoir is a bad idea. Bitreservoir always has a positive effect on quality. d) There is a widespread misconception about bitrate. In an mp3 file there are two kinds of bitrates. The most important bitrate is that of the audio data. But the audio data are packaged into frames (containers for the audio data) which have their own bitrates (which corresponds to the size of these containers). Bitreservoir allows audio data to spread over several frames. That's why there is only a loose relation between audio data bitrate and frame bitrate. When you demand Lame to keep bitrate at 256 kbps or above this is a specification for the frame bitrate, not the audio data bitrate. When you additionally disable bitreservoir you don't change audio data at all. You just use bigger containers for the same audio data. You have a lot of unused bits in your files. You can figure that out by using the mp3packer tool on your files. You'll get smaller files with exactly the same audio data (to ensure yourself that I'm not talking nonsense you can use foobar's bit-compare track tool). If you keep bitreservoir enabled this can have a positive quality effect when keeping (frame) bitrate at 256 kbps or above because this way the amount of data available in the bitreservoir will be a bit higher than when using the default settings. But you should use mp3packer afterwards to squeeze the many unused bits out of the file. And you should use 320 kbps as the general frame bitrate - when using mp3packer afterwards average bitrate won't increase. e) With very high bitrate settings as you use them audible deviation from the original is very rare but it can happen. The essential question is how to deal with this situation, and you will find two groups of people here which often can't understand the other group's attitude. The probably major group feels like 'I don't care about rare events when quality isn't great. Usually quality is perfect, and when it isn't it's usually not annoying.' These people usually use -V2 or similar according to their personal attitude and needs. Sometimes they are additionally proud of going this way because they use their bits very effeciently and think it's a misuse of a lossy encoder to make use of it in a less efficient way. Compared to this group the other group is a bit paranoid. Audible issues even when they are rare give them an uncomfortable feeling. They want to be very much on the safe side. Usually they still care about file size, but to a very minor extent especially as these days sufficient storage space usually is available or can be made available even on portable devices at low price. I personally belong to the paranoid group, and you sound very much like you do too. My advice: use lame3100i, a functional extension . lame3100i has a minimum audio data bitrate feature for instance, something that you obviously want to use but can't get with standard Lame which just allows for defining the mnimum frame bitrate.