E-mu disk images: share the audio of a sample between the zones which play it

[douglas-carmichael]

Converting from an E-mu library CD-ROM image runs out of memory on a normal Java heap, because reading the image creates a separate copy of the audio of a sample for every zone which plays it.

The presets of a bank map the same samples over and over: the first volume of the 'Emulator Standards' library plays 1480 samples from 25580 zones. Its 304 MB image therefore held 3.5 GB of audio while it was read, instead of the 192 MB it contains. With a Java heap smaller than that the run ends with Java heap space and no presets at all - and since the message is logged and the run then reports Finished., it reads like a successful conversion which found nothing:

Reading Emulator III bank 'Stereo Strings' with 13 preset(s) and 14 sample(s).
Java heap space
Finished.

The audio of a sample is now decoded once per channel selection - stereo, or the single channel which is left when a zone mutes one side - and shared by all zones which play it, whether or not they belong to the same preset. The zones of a chorus pair already shared their data this way, and the Emulator IV and Kurzweil detectors already keep their sample data per sample instead of per zone.

The second commit fixes the same image being read twice: the Emulator III and the EOS samplers share the file system and neither can read the banks of the other, so the generic ISO/IMG format tries both on the same image, and reading the files of an image reads all of their content. The files are now read once and offered to both formats.

Measured on Vol1_EmulatorStandards.iso (304 MB):

	before	after
audio held while reading	3521 MB	192 MB
distinct copies of audio	21903	1480
smallest heap which reads the image	over 512 MB, fails	512 MB
Analyse run, 4 GB heap	9.7 s	7.8 s

Verified against the unchanged version by digesting every zone of the image - SHA-256 of its audio plus key range, root key, velocity range, tuning, gain, panning and loops: all 25580 zones of its 1255 presets are identical, as is the full log of an Analyse run. An EOS CD-ROM image (812 presets) also reads identically and still needs the same heap, since only its number of reads changes.