afGetFrameSize(3dm)afGetFrameSize(3dm)NAME
afGetFrameSize, afGetVirtualFrameSize - get the track / virtual frame
size in bytes for a specified audio track from an AFfilehandle structure
SYNOPSIS
#include <dmedia/audiofile.h>
int afGetFrameSize(AFfilehandle file, int track, int extend3to4)
int afGetVirtualFrameSize(AFfilehandle file, int track, int extend3to4)
PARAMETER
file is an AFfilehandle structure, previously created by a call
to afOpenFile(3dm).
track is an integer which identifies an audio track in file.
extend3to4 is a integer boolean value (i.e., 0 or 1) indicating whether
the routine should extend the value of the frame size for
24-bit uncompressed data out to 32 bits.
Since all currently supported file formats contain exactly
one audio track per file, the constant AF_DEFAULT_TRACK
should always be used here for now.
RETURN VALUEafGetFrameSize() returns the size in bytes of a sample frame in the file
referenced by track. afGetVirtualFrameSize() returns size in bytes of a
sample frame in the audio buffer as specified by the current virtual
format. See afIntro(3dm) for an explanation of virtual format.
In case of error, -1 is returned.
DESCRIPTIONafGetFrameSize() returns the size of a sample frame in an audio track in
the file represented by the AFfilehandle argument.
afGetVirtualFrameSize() does the same for the virtual format for the
given track, as set by any combination of calls to
afSetVirtualSampleFormat(3dm) and afSetVirtualChannels(3dm).
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
pair.
The extend3to4 allows the application to choose, in the case where 24-bit
uncompressed data is present in the file associated with track, whether
to return the actual size in bytes of a frame of data in that track (3 *
number_of_channels) or the size of the frames which will be presented to
the user (since this will always be 4-byte sign-extended integer). The
former is useful for informational purposes, but the latter is necessary
for determining the size of the audio buffer to be handed to
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afGetFrameSize(3dm)afGetFrameSize(3dm)afReadFrames(3dm). Note that extend3to4 only applies to 24-bit sample
width. It is ignored in all other cases.
SEE ALSOafWriteFrames(3dm), afReadFrames(3dm), afGetChannels(3dm),
afGetVirtualChannels(3dm), afSetVirtualSampleFormat(3dm)
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