dpawson@oracle.com (03/27/91)
Hey folks,
Sorry - I'm sure this has been covered before, but I never was particularly
interested in the past. Does anybody have any experience playing Mac sampled
sounds on a Sparc? If so, please drop me a note telling me what I am missing.
I sampled at 7.4 khz on the Mac, then transferred to a Sparc using binary mode
ftp. When I play back, my sounds are *very* loud, and while the true message
is barely audible in the background, it sounds remarkably like a vacuum
cleaner.
Thanks in advance,
Dave Pawson
dpawson@oracle.combruner@sp15.csrd.uiuc.edu (John Bruner) (03/27/91)
For some time I've been tempted to write a program to convert Mac 'snd ' resources into SPARC audio files. However, I never seem to assemble all of the necessary documentation (Mac + Sun) in one place at the same time. The Sun audio files are sampled at 8kHz and are stored in an encoded format. The Sun documentation refers to this as ISDN "mu-law" encoding, which I'm sure is a standard encoding but to which I have no reference. According to the Sun audio_ulaw2linear(3) manual page "The u-law transfer function results in a nearly linear relationship to PCM [Pulse Code Modulated] at low amplitudes and a logarithmic relationship at high amplitudes. Another wrinkle is that the audio is stored in one's complement sign-magnitude format on the Sun. Sun's documentation indicates that the format of its audio files is a subset of the format on the NeXT. I've heard that there is a program that converts Mac <-> NeXT audio formats, but I haven't tracked it down yet. If you just FTP'd the sound in binary, then the Sun "play" program probably assumed some default format for the data, most likely 8-bit mu-law encoding sampled at 8kHz. I suspect this accounts for the "vacuum cleaner" you're hearing. -- John Bruner Center for Supercomputing R&D, University of Illinois bruner@csrd.uiuc.edu (217) 244-4476
russotto@eng.umd.edu (Matthew T. Russotto) (03/28/91)
In article <1991Mar27.015629.9536@oracle.com> dpawson@oracle.com () writes: >Hey folks, > Sorry - I'm sure this has been covered before, but I never was particularly >interested in the past. Does anybody have any experience playing Mac sampled >sounds on a Sparc? If so, please drop me a note telling me what I am missing. >I sampled at 7.4 khz on the Mac, then transferred to a Sparc using binary mode >ftp. When I play back, my sounds are *very* loud, and while the true message >is barely audible in the background, it sounds remarkably like a vacuum >cleaner. A guess: Mac sounds are in 'offset binary'-- the position of the speaker changes continuously as you move from 0 to 255. Sparc sounds are probably in two's complement, which would mean that the speaker position would change continuously from 0 to 127, with a discontinuity at 128 (-128), and then move continuously from 128 (-128) to 255 (-1). Try subtracting 128 from each byte in the mac file. -- Matthew T. Russotto russotto@eng.umd.edu russotto@wam.umd.edu .sig under construction, like the rest of this campus.
daveh@ccwf.cc.utexas.edu (David H. Huang) (03/28/91)
In article <BRUNER.91Mar27085814@sp15.csrd.uiuc.edu> bruner@sp15.csrd.uiuc.edu (John Bruner) writes: >For some time I've been tempted to write a program to convert Mac 'snd ' >resources into SPARC audio files. However, I never seem to assemble >all of the necessary documentation (Mac + Sun) in one place at the >same time. There's already a program that you can run on the Sun end to convert Mac format to Sun audio format. The source for mac2sun is available for FTP from emx.utexas.edu in the /pub/mnt/source/sun/ss-audio directory. >-- >John Bruner Center for Supercomputing R&D, University of Illinois > bruner@csrd.uiuc.edu (217) 244-4476 -- David Huang | "Calzoni Pizza: Internet: daveh@ccwf.cc.utexas.edu | Delivery in six UUCP: ..!ut-emx!ccwf.cc.utexas.edu!daveh | hours, or else your America Online: DrWho29 | pizza is cold."