Converting mp2 to wav with Graphedit

[Pojken Purken]

I've converted an mpa-stream to wav with Graphedit. When I do a frequency analysis on the wav I find these spikes every 1500Hz after 16.5kHz and up (se picture).

http://www.algonet.se/~mwe/spikes.gif

I don't know if they are present in the original audio or if they are artifacts of the conversion. I've used the following default DirectShow-filters in Windows 2000:

MPEG-I Stream Splitter
MPEG Audio Decoder (Microsoft version 2.0)

If the spikes are artifacts, are there any suggestions of other filters that will do a better job converting the mpa-stream?

Regards
PP

[DSPguru]

i have no clue of where those high frequencies came from, but why won't you pass your signal thru a low-pass filter ?

[Pojken Purken]

Exactly what I've been doing so far... but if it's the filters that are causing them it would be better to remove the source. Isn't it common when you're resampling a signal that you end up with some digital noise? Could it be the same phenomenon here?
/PP

[Neo Neko]

CDeX will convert MPEG1 and 2 streams to WAV or other formats. It does so outside of directshow as far as I know. So it might be able to help.

[Pojken Purken]

I'll see if I can find it and give it a try.

BTW I replaced the Microsoft filter with Cyberlink's but the results were exactly the same.

/PP

[Pojken Purken]

Found CDeX and voila - no spikes! Now, if someone can explain this for me... :-P

/PP

[DSPguru]

better decoding engine.

btw,
BeSweet also capable of decoding mp2.