Filburt
Headphoneus Supremus
- Joined
- Jun 23, 2005
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Quote:
If you understand what I tried to explain to you, it would follow that the graphs alone do not give you an idea of how it sounds. Psychoacoustics is much more complex than this, and a solid analysis will require more than what information is presented in these graphs.
Quote:
Is this in response to my post? My criticism of his graphs and conclusions was scientific. If anything, the conclusions being made here about codecs based on their respective graphs are the sort of undersupported conjecturing and pseudo-science you seem to be criticising. You have to ABX codecs in order to get relevant data with which to judge lossy codecs. They're based on psychoacoustics, which inherently reduces to a perceptual domain. However, psychoacoustics is a scientific field, based on data and theories resting upon it and after data collection you can make analysis and develop scientific models and theories, along with make predictions based off of them. In order to do so, though, you still need that initial data.
Furthermore, psy models are primarily tuned for _real music_; not test tones that are unlikely to mirror a realistic scenario, created to try to trick the psy model. Those tests are useful when trying to isolate a problem, or improve performance after having solved problems with actual music, but the failure of a psy model on something highly synthetic is hardly dispositive of the global performance of the model. HE-AAC, for example, uses SBR which can actually work fairly well with many songs, especially when taking into account a low target bitrate, but it is unlikely to perform well in some circumstances, such as probably those of this type. Another thing to consider is that what shows as visible loss in some areas may not necessarily indicate poor performance. The fact of the matter is, as per the very foundations of psychoacoustics, you cannot hear all which is available in the source data, and it's the job of the psy model to figure out what you can and cannot hear. A graph that may show some visible loss may indicate the psy model was able to better figure out what was inaudible than that of another codec, and so was able to dedicate more bandwidth to that which is audible in the source.
I'll reiterate my earlier point. Lossy compression's focus is maximisation of quantitative loss with minimisation of qualitative loss. These graphs are unlikely to be sufficient for the purposes of making a well-reasoned, defensible analysis of the qualitative performance of a codec, especially without a working background in psychoacoustic theory and analysis.
Originally Posted by Sir Nobax /img/forum/go_quote.gif however it gives an IDEA how it sounds. |
If you understand what I tried to explain to you, it would follow that the graphs alone do not give you an idea of how it sounds. Psychoacoustics is much more complex than this, and a solid analysis will require more than what information is presented in these graphs.
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Originally Posted by audiomagnate /img/forum/go_quote.gif Get used to it. Anything remotely based on real science around here gets flamed. You have to understand that accurate sound reproduction is more of a religion than a science to most of these people, and you're an atheist who's telling them there is no god. You should have started a thread about how changing the power cord on your CD player made the most amazing improvement in sound you've ever heard through your KSC-75s. Then you'ld be feeling the love right now. I think the complexity of the test wave form, combined with how easy it is to see aberrations, is a great idea. I think it's excellent, well thought out stuff. Keep up the good work! |
Is this in response to my post? My criticism of his graphs and conclusions was scientific. If anything, the conclusions being made here about codecs based on their respective graphs are the sort of undersupported conjecturing and pseudo-science you seem to be criticising. You have to ABX codecs in order to get relevant data with which to judge lossy codecs. They're based on psychoacoustics, which inherently reduces to a perceptual domain. However, psychoacoustics is a scientific field, based on data and theories resting upon it and after data collection you can make analysis and develop scientific models and theories, along with make predictions based off of them. In order to do so, though, you still need that initial data.
Furthermore, psy models are primarily tuned for _real music_; not test tones that are unlikely to mirror a realistic scenario, created to try to trick the psy model. Those tests are useful when trying to isolate a problem, or improve performance after having solved problems with actual music, but the failure of a psy model on something highly synthetic is hardly dispositive of the global performance of the model. HE-AAC, for example, uses SBR which can actually work fairly well with many songs, especially when taking into account a low target bitrate, but it is unlikely to perform well in some circumstances, such as probably those of this type. Another thing to consider is that what shows as visible loss in some areas may not necessarily indicate poor performance. The fact of the matter is, as per the very foundations of psychoacoustics, you cannot hear all which is available in the source data, and it's the job of the psy model to figure out what you can and cannot hear. A graph that may show some visible loss may indicate the psy model was able to better figure out what was inaudible than that of another codec, and so was able to dedicate more bandwidth to that which is audible in the source.
I'll reiterate my earlier point. Lossy compression's focus is maximisation of quantitative loss with minimisation of qualitative loss. These graphs are unlikely to be sufficient for the purposes of making a well-reasoned, defensible analysis of the qualitative performance of a codec, especially without a working background in psychoacoustic theory and analysis.