| Author |
Message |
BoBo
Staff
Joined: 29 Jul 2003
Posts: 5233
Location: Split
|
 Posted: Fri Jul 23, 2004 1:23 pm Post subject: Escape from lossyness (mp3 detection guide) |
 |
|
Moved to http://www.maiden-world.com/live/MP3_Detection_Guide
#################### UNDER CONSTRUCTION ####################
1) Forget about mp3 detection programs. They are useless because they use same technic as you with your eyes. There is no way they can detect more accurately. They can only create confusion. Checking for compression artifacts inside wave form is different story, but those programs do not exist.
2) Forget about spectral analysis. It's useless, because freq. analysis is much more accurate. You can't see dynamic changes with spectral analysis and that's the most important part in detecting mp3s. It's easy to see typical cut at 16 kHz, but everything else is not that easy.
3) Use only freq. analysis and your eyes.
#################### UNDER CONSTRUCTION ####################
Last edited by BoBo on Thu Oct 07, 2004 12:06 pm; edited 4 times in total |
|
| Back to top |
|
 |
BoBo
Staff
Joined: 29 Jul 2003
Posts: 5233
Location: Split
|
| Posted: Sat Jul 24, 2004 8:27 pm Post subject: |
|
|
Typical mp3 (128 kbps CBR). It has cut at 16 kHz.
 |
|
| Back to top |
|
|
BoBo
Staff
Joined: 29 Jul 2003
Posts: 5233
Location: Split
|
| Posted: Sat Jul 24, 2004 8:28 pm Post subject: |
|
|
96 kbps CBR mp3 has cut at 12 kHz and 40 kbps CBR at 6 kHz.
  |
|
| Back to top |
|
|
BoBo
Staff
Joined: 29 Jul 2003
Posts: 5233
Location: Split
|
| Posted: Sat Jul 24, 2004 8:29 pm Post subject: |
|
|
mp3s with a bitrate > 128 kbps CBR still have cut at 16 kHz, but encoder includes frequencies above 16 kHz too, as you can see on this four pictures. Cut is still detectable, but you have to watch freq. analysis while track is playing.
 
  |
|
| Back to top |
|
|
BoBo
Staff
Joined: 29 Jul 2003
Posts: 5233
Location: Split
|
| Posted: Sat Jul 24, 2004 8:30 pm Post subject: |
|
|
128 kbps VBR mp3 has cut at 15.5 kHz, but frequencies bellow 15.5 kHz have similar behaviour as frequencies above 16 kHz in previous cases.
  |
|
| Back to top |
|
|
BoBo
Staff
Joined: 29 Jul 2003
Posts: 5233
Location: Split
|
| Posted: Sat Jul 24, 2004 8:51 pm Post subject: |
|
|
Here is example of ATRAC compression used while recoding with minidisc (Sony MZ-N710, ATRAC3) in SP mode
 
 
Last edited by BoBo on Sun Jul 25, 2004 3:47 pm; edited 1 time in total |
|
| Back to top |
|
|
BoBo
Staff
Joined: 29 Jul 2003
Posts: 5233
Location: Split
|
| Posted: Sun Jul 25, 2004 3:27 pm Post subject: |
|
|
Here is example of ATRAC compression used while recoding with minidisc (Sony MZ-N710, ATRAC3) in LP2 mode
 
 
Last edited by BoBo on Sun Jul 25, 2004 3:47 pm; edited 1 time in total |
|
| Back to top |
|
|
BoBo
Staff
Joined: 29 Jul 2003
Posts: 5233
Location: Split
|
| Posted: Sun Jul 25, 2004 3:31 pm Post subject: |
|
|
Here is example of ATRAC compression used while recoding with minidisc (Sony MZ-N710, ATRAC3) in LP4 mode
 
  |
|
| Back to top |
|
|
|
