According to Mark Callow (msc@sgi.com):

Benjamin Denckla (bdenckla@husc.harvard.edu) writes:

An important file format for the Mac which is only mentioned once in theFAQ is the Sound Designer II file format. There is also an older SoundDesigner I format. I have the SDII format in electronic form but I don't think I'm at liberty to distribute it. It can be obtained by applying to become a 3rd Party Developer for Digidesign. This process is simple(1-page application) and free. Call Digidesign at 415-688-0600 for information. The SDII file format is interesting in that all non-sampledata (sample rate, channels, etc.) is contained in the resource fork andthe data fork contains sample data only.

The NeXT/Sun audio file format

Here's the complete story on the file format, from the NeXT documentation. (Note that the "magic" number is ((int)0x2e736e64),which equals ".snd".) Also, at the end, I've added a litte document that someone posted to the net a couple of years ago, that describesthe format in a bit-by-bit fashion rather than from C.

I received this from Doug Keislar, NeXT Computer. This is also the Sun format, except that Sun doesn't recognize as many format codes. I added the numeric codes to the table of formats and sorted it.

SNDSoundStruct: How a NeXT Computer Represents Sound

The NeXT sound software defines the SNDSoundStruct structure to represent sound. This structure defines the soundfile and Mach-O sound segment formats and the sound pasteboard type. It's also used to describe sounds in Interface Builder. In addition, each instance of the Sound Kit's Sound class encapsulates a SNDSoundStruct and provides methods to access and modify its attributes.

Basic sound operations, such as playing, recording, and cut-and-paste editing, are most easily performed by a Sound object. In many cases, the Sound Kit obviates the need for in-depth understanding of the SNDSoundStruct architecture. For example, if you simply want to incorporate sound effects into an application, or to provide a simple graphic sound editor (such as the one in the Mail application), you needn't be aware of the details of the SNDSoundStruct. However, if you want to closely examine or manipulate sound data you should be familiar with this structure.

The SNDSoundStruct contains a header, information that describes the attributes of a sound, followed by the data (usually samples) that represents the sound. The structure is defined (in sound/soundstruct.h) as:

typedef struct {

int magic; /* magic number SND_MAGIC */

int dataLocation; /* offset or pointer to the data */

int dataSize; /* number of bytes of data */

int dataFormat; /* the data format code */

int samplingRate; /* the sampling rate */

int channelCount; /* the number of channels */

char info[4]; /* optional text information */

SNDSoundStruct Fields

magic

magic is a magic number that's used to identify the structure as a SNDSoundStruct. Keep in mind that the structure also defines the soundfile and Mach-O sound segment formats, so the magic number is also used to identify these entities as containing a sound.

dataLocation

It was mentioned above that the SNDSoundStruct contains a header followed by sound data. In reality, the structure only contains the header; the data itself is external to, although usually contiguous with, the structure. (Nonetheless, it's often useful to speak of the SNDSoundStruct as the header and the data.) dataLocation is used to point to the data. Usually, this value is an offset (in bytes) from the beginning of the SNDSoundStruct to the first byte of sound data.
The data, in this case, immediately follows the structure, so dataLocation can also be thought of as the size of the structure's header. The other use of dataLocation, as an address that locates data that isn't contiguous with the structure, is described in "Format Codes," below.

dataSize, dataFormat, samplingRate, and channelCount

These fields describe the sound data.

dataSize is its size in bytes (not including the size of the SNDSoundStruct).

dataFormat is a code that identifies the type of sound. For sampled sounds, this is the quantization format. However, the data can also be instructions for synthesizing a sound on the DSP. The codes are listed and explained in "Format Codes," below.

samplingRate is the sampling rate (if the data is samples). Three sampling rates, represented as integer constants, are supported by the hardware:

Constant	Sampling Rate (samples/sec)
SND_RATE_CODEC	8012.821 (CODEC input)
SND_RATE_LOW	22050.0 (low sampling rate output)
SND_RATE_HIGH	44100.0 (high sampling rate output)

channelCount is the number of channels of sampled sound.

info

info is a NULL-terminated string that you can supply to provide a textual description of the sound. The size of the info field is set when the structure is created and thereafter can't be enlarged. It's at least four bytes long (even if it's unused).

Format Codes

A sound's format is represented as a positive 32-bit integer. NeXT reserves the integers 0 through 255; you can define your own format and represent it with an integer greater than 255. Most of the formats defined by NeXT describe the amplitude quantization of sampled sound data:

Value	Code	Format
0	SND_FORMAT_UNSPECIFIED	unspecified format
1	SND_FORMAT_MULAW_8	8-bit mu-law samples
2	SND_FORMAT_LINEAR_8	8-bit linear samples
3	SND_FORMAT_LINEAR_16	16-bit linear samples
4	SND_FORMAT_LINEAR_24	24-bit linear samples
5	SND_FORMAT_LINEAR_32	32-bit linear samples
6	SND_FORMAT_FLOAT	floating-point samples
7	SND_FORMAT_DOUBLE	double-precision float samples
8	SND_FORMAT_INDIRECT	fragmented sampled data
9	SND_FORMAT_NESTED	?
10	SND_FORMAT_DSP_CORE	DSP program
11	SND_FORMAT_DSP_DATA_8	8-bit fixed-point samples
12	SND_FORMAT_DSP_DATA_16	16-bit fixed-point samples
13	SND_FORMAT_DSP_DATA_24	24-bit fixed-point samples
14	SND_FORMAT_DSP_DATA_32	32-bit fixed-point samples
15	?
16	SND_FORMAT_DISPLAY	non-audio display data
17	SND_FORMAT_MULAW_SQUELCH	?
18	SND_FORMAT_EMPHASIZED	16-bit linear with emphasis
19	SND_FORMAT_COMPRESSED	16-bit linear with compression
20	SND_FORMAT_COMPRESSED_EMPHASIZED	A combination of the two above
21	SND_FORMAT_DSP_COMMANDS	Music Kit DSP commands
22	SND_FORMAT_DSP_COMMANDS_SAMPLES	?

[Some new ones supported by Sun. This is all I currently know. --GvR]

23	SND_FORMAT_ADPCM_G721
24	SND_FORMAT_ADPCM_G722
25	SND_FORMAT_ADPCM_G723_3
26	SND_FORMAT_ADPCM_G723_5
27	SND_FORMAT_ALAW_8

Most formats identify different sizes and types of sampled data.
Some deserve special note:

-- SND_FORMAT_DSP_CORE format contains data that represents a loadable DSP core program. Sounds in this format are required by the SNDBootDSP() and SNDRunDSP() functions. You create a SND_FORMAT_DSP_CORE sound by reading a DSP load file (extension ".lod") with the SNDReadDSPfile() function.

-- SND_FORMAT_DSP_COMMANDS is used to distinguish sounds that contain DSP commands created by the Music Kit. Sounds in this format can only be created through the Music Kit's Orchestra class, but can be played back through the SNDStartPlaying() function.

-- SND_FORMAT_DISPLAY format is used by the Sound Kit's SoundView class. Such sounds can't be played.

-- SND_FORMAT_INDIRECT indicates data that has become fragmented, as described in a separate section, below.

-- SND_FORMAT_UNSPECIFIED is used for unrecognized formats.

Fragmented Sound Data

Sound data is usually stored in a contiguous block of memory. However, when sampled sound data is edited (such that a portion of the sound is deleted or a portion inserted), the data may become discontiguous, or fragmented. Each fragment of data is given its own SNDSoundStruct header; thus, each fragment becomes a separate SNDSoundStruct structure. The addresses of these new structures are collected into a contiguous, NULL-terminated block; the dataLocation field of the original SNDSoundStruct is set to the address of this block, while the original format, sampling rate, and channel count are copied into the new SNDSoundStructs.

Fragmentation serves one purpose: It avoids the high cost of moving data when the sound is edited. Playback of a fragmented sound is transparent-you never need to know whether the sound is fragmented before playing it. However, playback of a heavily fragmented sound is less efficient than that of a contiguous sound. The SNDCompactSamples() C function can be used to compact fragmented sound data.

Sampled sound data is naturally unfragmented. A sound that's freshly recorded or retrieved from a soundfile, the Mach-O segment, or the pasteboard won't be fragmented. Keep in mind that only sampled data can become fragmented.

_________________________
From mentor.cc.purdue.edu!purdue!decwrl!ucbvax!ziploc!eps Wed Apr 4 23:56:23 EST 1990
Article 5779 of comp.sys.next:
Path: mentor.cc.purdue.edu!purdue!decwrl!ucbvax!ziploc!eps
From: eps@toaster.SFSU.EDU (Eric P. Scott)
Newsgroups: comp.sys.next
Subject: Re: Format of NeXT sndfile headers?
Message-ID: <445@toaster.SFSU.EDU>
Date: 31 Mar 90 21:36:17 GMT
References:14978@phoenix.Princeton.EDU
Reply-To: eps@cs.SFSU.EDU (Eric P. Scott)
Organization: San Francisco State University
Lines: 42


In article 14978@phoenix.Princeton.EDU

bskendig@phoenix.Princeton.EDU (Brian Kendig) writes:

I'd like to take a program I have that converts Macintosh sound files to NeXT sndfiles and polish it up a bit to go the other direction aswell.

Two people have already submitted programs that do this(Christopher Lane and Robert Hood); check the variousNeXT archive sites.

Could someone please give me the format of a NeXT sndfileheader?

 
"big-endian" 
        0       1       2       3 
        +-------+-------+-------+-------+ 
0       | 0x2e  | 0x73  | 0x6e  | 0x64  |       "magic" number 
        +-------+-------+-------+-------+ 
4       |                               |       data location 
        +-------+-------+-------+-------+ 
8       |                               |       data size 
        +-------+-------+-------+-------+ 
12      |                               |       data format (enum) 
        +-------+-------+-------+-------+ 
16      |                               |       sampling rate (int) 
        +-------+-------+-------+-------+ 
20      |                               |       channel count 
        +-------+-------+-------+-------+ 
24      |       |       |       |       |       (optional) info string 
 

28 = minimum value for data location

data format values can be found in /usr/include/sound/soundstruct.h

Most common combinations:

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