stateVars
#include <Sound.h>
Ptr samplePtr; 4 0 if NIL then samples are in sampleArea
re presentation
unsigned char encode; 1 20 data structure used , stdSH,
extSH, or cmpSH
unsigned char baseFrequency; 1 21 baseFrequency value
extended AIFFSampleRate; 10 26 IEEE sample rate
Ptr markerChunk; 4 36 sync track Ptr futureUse1; 4 40 reserved by Apple Ptr futureUse2; 4 44 reserved by Apple between compression calls
unsigned short compressionID; 2 56 0 means no compression, non
zero means compressionID
unsigned short packetSize; 2 58 number of bits in compressed
sample packet
unsigned short snthID; 2 60 resource ID of
contains NRT C/E
unsigned short sampleSize; 2 62 number of bits in
non-compressed sample
char sampleArea[1]; 1 64 space for when samples follow
directly
typedef CmpSoundHeader *CmpSoundHeaderPtr;
Field descriptions
samplePtr Indicates the location of the compressed sound frames.
If samplePtr is NIL, then the frames are located in the
sampleArea field of the
compressed sound header. Otherwise, samplePtr
points to a buffer that contains the frames.
numChannels Indicates how many channels are in the sample.
sampleRate Indicates the sample rate at which the frames were
sampled before compression. The approximate sample
rates are shown in the Table "Sample Rates". under the
declared as a Fixed data type, but the most significant bit is not treated as a sign bit; instead, that bit is
interpreted as having the value 32,768.
loopStart Indicates the beginning of the loop points of the sound
before compression.
loopEnd Indicates the end of the loop points of the sound before
compression.
encode Indicates the method of encoding (if any) used to
generate the sampled sound data. For a
compressed sound header, you should specify the
constant cmpSH Encode option values in the ranges 0
through 63 and 128 to 255 are reserved for use by
Apple. You are free to use numbers in the range 64
through 127 for your own encode options.
baseFrequency Indicates the pitch of the original sampled sound. It is
not used by bufferCmd. If you wish to make use of
baseFrequency with a compressed sound, you must first
expand it and then play it with soundCmd and
numFrames Indicates the number of frames contained in the
compressed sound header. When you store multiple
channels of uncompressed sound, store them as
interleaved sample frames (as in AIFF). When you
store multiple channels of compressed sounds, store
them as interleaved packet frames.
AIFFSampleRate Indicates the sample rate at which the frames were
sampled before compression, as expressed in an
extended data type re presentation.
markerChunk Specifies synchronization information. The
markerChunk field is not presently used and should be
set to NIL.
futureUse1 Reserved.
futureUse2 The two futureUse fields are reserved for use by
Apple. To maintain compatibility with future releases
of system software, you should always set these fields
to 0.
stateVars Points to a state block record. The stateVars field is
used to store the state variables for a given algorithm
across consecutive calls.
leftOverSamples Points to a left over block record. You can use this
block to store samples that will be truncated across
algorithm invocations.
compressionID Identifies the compression algorithm used on the
samples in the compressed sound header. You can use a
constant to define the compression algorithm.
notCompressed noncompressed samples
threeToOne 3:1 compressed samples
sixToOne 6:1 compressed samples
Apple reserves the right to use compression IDs in the
range 0 through 511.
packetSize Indicates the size, specified in bits, of the smallest
element that a given expansion algorithm can work
with. You can use a constant to define the packet size.
sixToOnePacketSize size for 6:1
threeToOnePacketSize size for 3:1
snthID Indicates the resource ID number of the 'snth'
resource that was used to compress the packets
contained in the compressed sound header. A 3:1 'snd '
resource would have a snthID of 11, and a 6:1 'snd '
would have a snthID of 13. If a
compressed sound header contains samples that are not
compressed, you should set the snthID field to 0.
sampleSize Indicates the size of the sample before it was
only with 8-bit samples. The samples should be in
offset binary format; applications that read their data
from AIFF files must convert the samples from two's
complement format to the binary format. The samples
passed in the compressed sound header should always be
byte-aligned, and any padding done to achieve byte
alignment should be done from the left with zeros.
sampleArea Contains the sample frames, but only when the
samplePtr field is NULL. Otherwise, the sample frames
are in the location indicated by samplePtr.
an 'snd ' resource that contains compressed sound data.
This resource has the same general structure as the 'snd ' resource
illustrated in The Format 1 'snd ' Resource in the section entitled
header is replaced by the compressed sound header. This example resource
specifies a monophonic sound compressed by using the 3:1 compression
algorithm.