Thanks.
I know about the Nokia's forum. The forum hasn't informations about  conversions between archives.
For example; I know that the Nokia PC Suite has a MP4 converter, but it is used only to convert heavy videos to the MP4 format, much more light format possible to be sent via MMS. The quality is condemnable. Mono sound, high and low frequencies cutted...Very bad!
The Nokia's phone support, confirmed it and the    
attendant explained that the 3GP is the appropriate configuration to have high quality videos on the mobile phones but heavy to be sent via MMS. This is the reason of the MP4 converter of Nokia PC Suite.
As I informed, using SUPER to convert  flv videos to 3GP (Sony Ericson and Nokia), with no trouble to configurate the audio CODEC , the result to Nokia 5200  was awesome.
Using these same videos in the 5310, the quality of video is excelent too, but the sound  is mono.
The SUPER has many configurations of AUDIO. Using the CODEC that presents 2 channels option,the sampling frequency must be higher or lower to the stereo be detected? The bit rate (kbps ) must be selected to higher or lower?
May be that some member of this forum may have already done similar tests, with    
success and, my intention is change some ideas about it.
Thank you for attention.

cescoe