afGetFormatParams(3dm)afGetFormatParams(3dm)NAMEafGetFormatParams - get the audio data format in an AFfilehandle for a
specified audio track via dmParams
SYNOPSIS
#include <dmedia/dm_audio.h>
#include <dmedia/audiofile.h>
DMstatus afGetFormatParams(AFfilehandle file, int track,
DMparams *params)
PARAMETER
file is an AFfilehandle structure, previously created by a call to
afOpenFile(3dm) or afOpenFD(3dm).
track is an integer which identifies an audio track in handle.
Since all currently supported file formats contain only one
audio track, the value AF_DEFAULT_TRACK should used here for
now.
params a DMparams list, previously created by a call to
dmParamsCreate(3dm).
DESCRIPTIONafGetFormatParams() retrieves all parameters associated with the audio
data in an AFfilehandle structure for an audio track. It obsoletes the
individual routines afGetSampleFormat(3dm), afGetChannels(3dm),
afGetRate(3dm), afGetCompression(3dm), and afGetCompressionParams(3dm).
The following parameters are defined in dmedia/dm_audio.h and may be
retrieved from params:
DM_AUDIO_FORMAT Sample format. Will be DM_AUDIO_TWOS_COMPLEMENT,
DM_AUDIO_UNSIGNED, DM_AUDIO_FLOAT, or
DM_AUDIO_DOUBLE.
DM_AUDIO_WIDTH Sample width in bits. For integer sample formats,
it will be an integer value between 1 and 32. For
format DM_AUDIO_FLOAT it will be 32, and for
DM_AUDIO_DOUBLE it will be 64.
DM_AUDIO_CHANNELS Channel count.
DM_AUDIO_RATE Sampling rate.
DM_AUDIO_COMPRESSION Compression type. Will be DM_AUDIO_UNCOMPRESSED or
one of the supported compression parameter values.
In addition, any parameters associated with the
compression, such as DM_AUDIO_BITRATE, will also be
retrievable here (see afGetCompression(3dm) and
afGetCompressionParams(3dm)).
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afGetFormatParams(3dm)afGetFormatParams(3dm)
DM_AUDIO_PCM_MAP_SLOPE
DM_AUDIO_PCM_MAP_INTERCEPT
DM_AUDIO_PCM_MAP_MAXCLIP
DM_AUDIO_PCM_MAP_MINCLIP
Slope, intercept, minimum and maximum clipping
values for PCM mapping (see
afGetVirtualPCMMapping(3dm) for a detailed
explanation).
When a file is opened for reading via a call to afOpenFile(3dm), the
track will contain a full description of the audio data format, including
data type, sample width, number of channels, sample rate, compression and
any associated parameters, and PCM mapping information.
CAVEATS
Note that this library will continue to support new file formats and thus
other data formats than the ones described above. Since the Audio File
Library is a Dynamic Shared Object (DSO), it is possible for this call to
return parameter values not found in <dmedia/dm_audio.h> at the time of
programming. Programs should be written to at least reject files with
formats they are not written to handle.
SEE ALSOafOpenFile(3dm), afReadFrames(3dm), afWriteFrames(3dm),
afInitFormatParams(3dm), afSetVirtualFormatParams(3dm),
afGetConversionParams(3dm)
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