VS1053B Datasheet, PDF (28/79 Pages) List of Unclassifed Manufacturers – Ogg Vorbis/MP3/AAC/WMA/MIDI AUDIO CODEC

VLSI
Solution ^y
VS1053b preliminary
VS1053B
8. FUNCTIONAL DESCRIPTION
8.2.5 Supported AAC (ISO/IEC 13818-7 and ISO/IEC 14496-3) Formats
VS1053b decodes MPEG2-AAC-LC-2.0.0.0 and MPEG4-AAC-LC-2.0.0.0 streams, i.e. the low com-
plexity profile with maximum of two channels can be decoded. If a stream contains more than one
element and/or element type, you can select which one to decode from the 16 single-channel, 16 channel-
pair, and 16 low-frequency elements. The default is to select the first one that appears in the stream.
Dynamic range control (DRC) is supported and can be controlled by the user to limit or enhance the
dynamic range of the material that contains DRC information.
Both Sine window and Kaiser-Bessel-derived window are supported.
For MPEG4 pseudo-random noise substitution (PNS) is supported. Short frames (120 and 960 samples)
are not supported.
Spectral Band Replication (SBR) level 3, and Parametric Stereo (PS) level 3 are supported (HE-AAC v2).
Level 3 means that maximum of 2 channels, samplerates upto and including 48 kHz without and with
SBR (with or without PS) are supported. Also, both mixing modes (R_a and R_b), IPD/OPD synthesis
and 34 frequency bands resolution are implemented. The downsampled synthesis mode (core coder
samplerates > 24 kHz and <= 48 kHz with SBR) is implemented.
SBR and PS decoding can also be disabled. Also different operating modes can be selected. See
config1 and sbrAndPsStatus in section 9.11 : ”Extra parameters”.
If enabled, the internal clock (CLKI) is automatically increased if AAC decoding needs a higher clock.
PS and SBR operation can also be automatically switched off if the internal clock is too slow for correct
decoding.
For AAC the streaming ADTS format is recommended. This format allows easy rewind and fast forward
because resynchronization is easily possible.
In addition to ADTS (.aac), MPEG2 ADIF (.aac) and MPEG4 AUDIO (.mp4 / .m4a) files are played,
but these formats are less suitable for rewind and fast forward operations. You can still implement these
features by using the safe jump points table, or using slightly less robust but much easier automatic
resync mechanism (see Section 9.5.4).
Because 3GPP (.3gp) and 3GPPv2 (.3g2) files are just MPEG4 files, those that contain only HE-AAC or
HE-AACv2 content are played.
Note: To be able to play the .3gp, .3g2, .mp4 and .m4a files, the mdat atom must be the last atom in
the MP4 file. Because VS1053b receives all data as a stream, all metadata must be available before the
music data is received. Several MP4 file formatters do not satisfy this requirement and some kind of
conversion is required. This is also why the streamable ADTS format is recommended.
Programs exist that optimize the .mp4 and .m4a into so-called streamable format that has the mdat atom
last in the file, and thus suitable for web servers’ audio streaming. You can use this kind of tool to process
files for VS1053b too. For example mp4creator -optimize file.mp4.
Version 0.5, 2007-12-03
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