afWriteFrames(3dm) afWriteFrames(3dm)
afWriteFrames - write audio sample frames to a specified track in an
audio file
#include <dmedia/audiofile.h>
int afWriteFrames(const AFfilehandle file, int track,
void *samples, const int count)
file expects the AFfilehandle structure for the audio file to which
audio sample data will be written. This structure is usually
the returned value of a call to afOpenFile(3dm).
track is an integer which identifies the audio track (chunk) in the
file to be accessed. Since all currently supported file
formats allow at most one audio track per file, the value
AF_DEFAULT_TRACK should always be used for this argument for
now.
samples is a pointer to a buffer containing samples to be written to
the audio file.
count expects the number of sample frames you want to write to the
audio track. For a stereo track, a sample frame would consist
of a <left, right> sample pair. For a monaural track, a sample
frame would be a single sample.
afWriteFrames() returns the number of sample frames written to the
internal track. The return value normally is greater than or equal to 0.
In the event of an error, afWriteFrames() will return -1, and the error
value can be retrieved via oserror(3C).
afWriteFrames() writes data to the specified track of an audio file from
the samples buffer.
afWriteFrames() attempts to write count sample frames from the samples
buffer to the track, starting at the current location of the file write
pointer within the track. samples should be of type signed char*,
unsigned char*, short*, int*, unsigned int*, float*, or double* depending
on the width and format of the samples in the audio track as set using
afInitSampleFormat(3dm).
When an audio file is opened with write access by afOpenFile(3dm) or
afOpenFD(3dm), the logical write pointer for the audio data is
initialized to point to the location of the first sample frame in the
track.
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afWriteFrames(3dm) afWriteFrames(3dm)
Before returning, afWriteFrames() automatically updates the logical write
pointer for track so that it points to the location of the sample frame
following the last one written to the file.
The samples buffer is interpreted differently depending on the current
configuration of the audio track. In particular, the sampwidth parameter
may or may not be meaningful, depending on what the sampfmt parameter is.
See afGetSampleFormat(3dm) for a full explanation of sample
representations.
afWriteFrames() automatically compresses data for audio tracks which are
encoded using the CCITT G.722, CCITT G.711, MPEG, and Aware
MultiRate/Lossless algorithms. The data is passed to afWriteFrames()
from an application program in the standard two's complement linear PCM
format, but this is by no means guaranteed for later compression types
(see afGetCompression(3dm) for more information about this). You select
a compression scheme for an audio track by calling
afInitCompression(3dm). To achieve real-time G.722 compression, the
application process may require non-degrading scheduling priority (see
schedctl(2) or npri(1))
If an audio track contains data for more than a single audio channel, the
data placed in the samples buffer should be interleaved. Sample data to
be written to a stereo file should be buffered as a sequence of
left/right pairs (sample "frames"). Interleave conventions for files
containing multichannel audio data are described in the AIFF-C
specification.
Example: to write 10000 stereo 16-bit sample pairs to a stereo AIFF-C
file, place 20000 individual samples (i.e., 10000 <left, right> sample
pairs) into a short[] buffer, and pass the buffer to afWriteFrames() with
count set to 10000.
This routine will 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
situation.
afOpenFile(3dm), afSeekFrame(3dm), afInitSampleFormat(3dm)
afWriteFrames(3dm) afWriteFrames(3dm)
afWriteFrames - write audio sample frames to a specified track in an
audio file
#include <dmedia/audiofile.h>
int afWriteFrames(const AFfilehandle file, int track,
void *samples, const int count)
file expects the AFfilehandle structure for the audio file to which
audio sample data will be written. This structure is usually
the returned value of a call to afOpenFile(3dm).
track is an integer which identifies the audio track (chunk) in the
file to be accessed. Since all currently supported file
formats allow at most one audio track per file, the value
AF_DEFAULT_TRACK should always be used for this argument for
now.
samples is a pointer to a buffer containing samples to be written to
the audio file.
count expects the number of sample frames you want to write to the
audio track. For a stereo track, a sample frame would consist
of a <left, right> sample pair. For a monaural track, a sample
frame would be a single sample.
afWriteFrames() returns the number of sample frames written to the
internal track. The return value normally is greater than or equal to 0.
In the event of an error, afWriteFrames() will return -1, and the error
value can be retrieved via oserror(3C).
afWriteFrames() writes data to the specified track of an audio file from
the samples buffer.
afWriteFrames() attempts to write count sample frames from the samples
buffer to the track, starting at the current location of the file write
pointer within the track. samples should be of type signed char*,
unsigned char*, short*, int*, unsigned int*, float*, or double* depending
on the width and format of the samples in the audio track as set using
afInitSampleFormat(3dm).
When an audio file is opened with write access by afOpenFile(3dm) or
afOpenFD(3dm), the logical write pointer for the audio data is
initialized to point to the location of the first sample frame in the
track.
Page 1
afWriteFrames(3dm) afWriteFrames(3dm)
Before returning, afWriteFrames() automatically updates the logical write
pointer for track so that it points to the location of the sample frame
following the last one written to the file.
The samples buffer is interpreted differently depending on the current
configuration of the audio track. In particular, the sampwidth parameter
may or may not be meaningful, depending on what the sampfmt parameter is.
See afGetSampleFormat(3dm) for a full explanation of sample
representations.
afWriteFrames() automatically compresses data for audio tracks which are
encoded using the CCITT G.722, CCITT G.711, MPEG, and Aware
MultiRate/Lossless algorithms. The data is passed to afWriteFrames()
from an application program in the standard two's complement linear PCM
format, but this is by no means guaranteed for later compression types
(see afGetCompression(3dm) for more information about this). You select
a compression scheme for an audio track by calling
afInitCompression(3dm). To achieve real-time G.722 compression, the
application process may require non-degrading scheduling priority (see
schedctl(2) or npri(1))
If an audio track contains data for more than a single audio channel, the
data placed in the samples buffer should be interleaved. Sample data to
be written to a stereo file should be buffered as a sequence of
left/right pairs (sample "frames"). Interleave conventions for files
containing multichannel audio data are described in the AIFF-C
specification.
Example: to write 10000 stereo 16-bit sample pairs to a stereo AIFF-C
file, place 20000 individual samples (i.e., 10000 <left, right> sample
pairs) into a short[] buffer, and pass the buffer to afWriteFrames() with
count set to 10000.
This routine will 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
situation.
afOpenFile(3dm), afSeekFrame(3dm), afInitSampleFormat(3dm)
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