Sherwood McGowan wrote: > I listened to all the demos you showed. > > My ear discerns a little muffling and minor "slushiness" in the GSM files > you sent, along with a much more narrow bandwidth, mainly on the high end > side, and Allison either has a mild whistling s or slushy s sound in her > voice or the producer didn't properly compress it to "de-ess" the recording. > Or, I could just be rather tired.
I don't think so. Everybody else I've played them for has made similar observations. > Either way, your best bet is to have the system use WAV files but also make > available GSM and ulaw versions of the same files. This is so that the > system can pick (and it does this automatically) the best format that > requires the least amount of CPU power for transcoding. If I remember > correctly, FXO/FXS cards can use straight PCM files. > > What I do to prepare a file is this: > > I record in 48Khz 32 bit mode (32 bit is just higher resolution so > processing has more to work with, 16 bit is fine since it's the end result), > then I compress with de-essing and pop removal (maximizes volume, removes > slushy or whistling s's and popping p's), then run through an FFT (Fast > Fourier Transform) to bring the frequency response within the natural range > of a telephone (if I remember correctly it's within the 300 - 4K range, I > can check if need be). How do you "de-ess" and remove pops? What filters do you use? > Then I reduce the file to a 8Khz, 16 bit mono file. Then I check the audio > again, and normalize (like compression but only raises the whole file to > where the highest peak of audio reaches the level requested, instead of > raising or lowering the level on a dynamic basis by using readahead of a > couple milliseconds). I usually normalize to around -3db. > > The end result is a WAV file that sounds good over the phone. I then put the > file on the asterisk server (or another server with sox installed) and > convert to gsm, ulaw, and alaw (using the original WAV, not using converted > gsm or whatever). > > Hope this was helpful, and I wish you luck. If nothing else, for like $50 or > so (depending on how many files there are) I would be willing to take a > series of WAV files from you and perform the filtering and whatnot for you, > and supply gsm, wav, ulaw, and alaw. > > I'm also going to just try and get a series of recordings together through > my partner's studio in Phoenix AZ, make the files available to the > community, and take up donations for the studio and processing time. > > Talk to you soon. I'm going to cc the asterisk-users list for this, so that > the community can benefit from the information. Thank you, Sherwood - you've been extremely helpful! I am going to try those steps you suggested (once I learn how to 'de-ess' and remove pops) but I may just take you up on the filtering and processing offer. -Stephen- _______________________________________________ --Bandwidth and Colocation sponsored by Easynews.com -- Asterisk-Users mailing list [email protected] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
