Notice : this aricle is my 2nd arcticle on mp3 tech and appeared on 31-5-7 on multiply site . The main reason writing that article is that many people are using low level MP3 compressions (as 192 adn 256 ) that i do not think are so necessary since per my measurements 128 kbps are more than enough. To my year wma's of the level of 48 kbps have neatly the same level .
--------- Given that many users on Multiply rip or covert their music in quite big files of over 7.5 MB fr a 4 minute song ,i decided to write this article to explain why it is not necessary to use very high sampling rates.
At same time I will notice to you why I use the WMA format in 48 kbps to include mass material into a small MP3 player as shown in my previous reviews
It is important to advise you that I was in the audio technology and HiFi's since 1980 , including also the MP3 tech form ca 1997 and my first ever MP3 player was with CD on 2000.Also i used several professional equipment the older days and I know very much about it.
| This is a abridged version of my blog in http://zlgr.multiply.com/journal/item/41 with a little more explanation in the pictorials If someone is still very boring to read this whole message ,please check the flies on the http://zlgr.multiply.com/journal/item/55 for his personal evaluation , though it is very worth of reading |
1.Make a file with white noise . This noise is used primarily for testing purposes in audio laboratories. it can be used to measure the linearity of audio systems including the audio part of radio transmitters. The easiest way to make this white noise is with the Cooledit program.
For best measurements i made a file of 60 secs making a file of 10M336B [10336 Kb]I also deliberately use the linear frequency response in order to find more easily the cutoff frequencies than with the standard logarithmic freq response
|This is our original WAV file's frequency response , designed from a white noise of 0 db level. As you may notice it is a totally linear, and will be used as reference to the results from various compressions shown later|
2.Convert the files toMP3 and /or WMA in the most popular conversions . I choose the MP3 format on 128 [standard]192 [broadcast mode ] and 256kb [store mode] while for WMA the 44 [FM] ,. 48[I say just CD] 64 [default near CD ]and 96 [CD ] kb.
I always used the Musicmatch Jukebox in its 6th version which is very light comparing to the newest versions and has very good results especially if converting from CDs and MPs to WMAs . And though Cooledit has MP3 save option
3.View the resulted files back to Coledit's frequency analysis screen
AS Cooledit cannot open WMA files , i used first a third party program to convert the WMA files iinto WAV and then opened with Cooledit , and here are the results :
Furthermore these are the results with the over mentioned program . I mean , using a different program to convert files gives a different result
AS for example Cooleditwith its MP3 plugin ca offer linear response to the maximum of the bandwidth.
At another example i was also using the ACE mult iformat converter . The results once opened or converted to WAV (for WMA) have made several interesting results . Please see the picture below, it is an animation!
From the above results , it is clear that ACE can technically offer better audio than MMJB on the MP3 format , but worse than MMJB in te WMA format