JEITA CP-3451
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5 Exif Audio File Specification
5.1 Outline of the Exif Audio File Specification
This chapter gives details of the audio file specification, covering the following items:
· Format version definition,
· Specifications relating to audio data,
· Basic structure of audio data,
· Chunks,
· File naming conventions.
5.2 Format Version
The version of the format specified here is recorded as 4 bytes (see section 0). The address bytes are recorded as
A1, A2, B1, B2, starting with the lowest number. A1 and A2 store the upper part of the standard version, with the
lower part stored in B1 and B2. When changes are made to the version number of this standard, the following rules
apply:
· When the changes are such that data readers can properly recognize conventional information and skip the
data that was recorded using newly added functions, the lower part of the version (B1, B2) is changed,
· When there is a possibility that a data reader implementing the old standard may operate incorrectly due to the
new specifications, the upper part of the version (A1, A2) is changed.
Players should be able to play back files of versions earlier than the supported standard.
5.3 Definition of Terms
Terms and notation are used as follows in this standard:
· Text enclosed in " " is a character string, and " "Z means a character string ending in NULL (00.H),
· ".H" appended to a numerical value means it is hexadecimal notation.
· Unless otherwise indicated, other numerical values are given in decimal notation.
5.4 Specifications Relating to Audio Data
5.4.1 Sampling Frequency
The sampling frequency shall be any of 8.000 kHz, 11.025 kHz, 22.050 kHz or 44.100 kHz. Only 8.000 kHz shall be
used for m
L AW PCM in accord with ITU-T G.711.
5.4.2 Bit Size
The bit size shall be 8 bits or 16 bits. Only 8 bits shall be used for m-LAW PCM in accord with ITU-T G.711; and
only 4 bits shall be used for IMA-ADPCM in accord with the IMA (Interoperability Multimedia Association)
specification.