Is it possible? If we have a mp3 file that doesn't use a reservoir, then is it possible to cut it perfectly on the frame boundaries, remove some part and then join it again?
Just a simple answer would be fine
Thanks.
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It depends on what "perfect" means. You'll get some uncancelled aliasing due to the MP3 filterbank. But it's fairly safe to assume that this will be less annoying than a possible click you get if you just cut out a block with your favorite wave editor.

Other than that it works. So, I'd say: YES.

Cheers,
SG

SebastianG, thank you for your replay.
Sorry for my delay, I was too busy these days.
So, going further with assumptions, if we have such (no bit reservoir) mp3 file, it should be possible to
- cut it in, say, three parts
- take the middle one and decode it to wav
- edit with appropriate wav editor
- convert it back to mp3
- stick together the three parts
Is it doable?
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It's still possible but more complicated than that. This is due to the mp3 filterbank. You should decode your full MP3, edit the result, encode it again and just replace some frames of the original MP3 by frames of the new one. This will work if...

• the bitreservoir isn't activated
• you don't alter the length (insert stuff or cut something out)
• you're using the same encoder and the decoder is compatible to the encoder in terms of encoder/decoder delay

Cheers,
SG