afGetFrameCount, AFgetframecnt, afGetTrackBytes, afGetDataOffset - get
the total sample frame count / data bytes / data offset for a specified
audio track from an AFfilehandle structure
AFframecount afGetFrameCount(AFfilehandle file, int track)
AFfileoffset afGetTrackBytes(AFfilehandle file, int track)
int afGetDataOffset(AFfilehandle file, int track)
file is an AFfilehandle structure, previously created by a call to
track is an integer which identifies an audio track in file.
Since all currently supported file formats contain exactly one
audio track per file, the constant AF_DEFAULT_TRACK should always
be used here.
afGetFrameCount() returns the total number of sample frames in track.
afGetTrackBytes() returns the total number of bytes of audio data in
track. afGetDataOffset() returns the offset in bytes to the beginning of
the audio data in track.
In case of error, -1 is returned by all of these routines.
afGetFrameCount(3dm) returns the current total number of sample frames in
an audio track in the file represented by the AFfilehandle argument.
In general, each sample frame in a given track consists of n samples,
where n is the value returned by afGetChannels(3dm) for track. For
monaural data, a sample frame consists of a single audio sample. For
stereo data, a sample frame consists of a <left, right> stereo sample
afGetTrackBytes() returns the total number of bytes of raw audio data
(i.e., prior to decompression) in track. This is useful for determining
raw file seek points, etc.
The return types AFframecount and AFfileoffset are large enough to hold
the maximum possible frame count value and maximum possible byte size,
respectively, for the current file system.
This routine may not function correctly if the user changes the file
position on the file descriptor for the AFfilehandle being manipulated.
See the section CAVEATS FOR USING THE HANDLE'S FILE DESCRIPTOR in
afIntro(3dm) for some important information about how to deal with this
afOpenFile(3dm), afWriteFrames(3dm), afReadFrames(3dm),
afGetChannels(3dm). afGetVirtualChannels(3dm), afSetVirtualChannels(3dm)
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