It’s not a bug, it’s a deliberate design decision. The first spectrogram frame takes N samples of audio data to compute; where should we say that the spectrogram frame is centered, on sample 0 or in the middle at sample N/2? It was decided that Raven would center the spectrogram frames on the center of the time window which comprises them, that is, at N/2. The width of a spectrogram frame is given by the hop size, so the only time the gap will not appear is when the hop size is equal to N (0% overlap).
Dean From: bounce-118726705-10098...@list.cornell.edu [mailto:bounce-118726705-10098...@list.cornell.edu] On Behalf Of Bill Evans Sent: Thursday, January 22, 2015 7:40 AM To: NFC-L Subject: [nfc-l] missing first few milliseconds of spectrograms made in Raven When I open a short night flight call wav file in Raven, the waveform window begins at 0 sec but the accompanying spectrogram window doesn't begin at zero -- it begins after a few milliseconds. See attached example. It’s not something that one would note unless they are working with very short sound files, and perhaps wish to use such a short spectrogram in a publication. Anyone else notice this possible bug in Raven? Bill Evans -- NFC-L List Info: Welcome and Basics<http://www.northeastbirding.com/NFC_WELCOME> Rules and Information<http://www.northeastbirding.com/NFC_RULES> Subscribe, Configuration and Leave<http://www.northeastbirding.com/NFC-L_SubscribeConfigurationLeave.htm> Archives: The Mail Archive<http://www.mail-archive.com/nfc-l@cornell.edu/maillist.html> Surfbirds<http://www.surfbirds.com/birdingmail/Group/NFC-L> BirdingOnThe.Net<http://birdingonthe.net/mailinglists/NFCL.html> Please submit your observations to eBird<http://ebird.org/content/ebird/>! -- -- NFC-L List Info: http://www.NortheastBirding.com/NFC_WELCOME http://www.NortheastBirding.com/NFC_RULES http://www.NortheastBirding.com/NFC-L_SubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/nfc-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/NFC-L 3) http://birdingonthe.net/mailinglists/NFCL.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
