Android MediaMetadataRetriever returns null values from most keys

I want to get information out of my media files (mp3 mostly) and I get only null from those values I want. I have tried all keys for extractMetadata(key). Am I skipping/missing something?

Code basis:

MediaMetadataRetriever f = new MediaMetadataRetriever();
f.setDataSource(item.getFilePath());

String title = f.extractMetadata(MediaMetadataRetriever.METADATA_KEY_TITLE);

I do get correct values with the duration key (MediaMetadataRetriever.METADATA_KEY_DURATION) and mimetype key (MediaMetadataRetriever.METADATA_KEY_MIMETYPE), which indicates that the datasource/filepath is working.

Poweramp (popular media player) is able to read metadata values, like title/author/composer etc. since it displays these extra values in the UI. Or perhaps Poweramp gets these values from some other source or method?

Any help is appreciated.