Datasheet

VS1053b Datasheet

8 SUPPORTED AUDIO DECODER FORMATS

8.5 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

complexity 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

and R

IPD/OPD synthesis and 34 frequency bands resolution are implemented. The downsampled

synthesis mode (core coder rates > 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 10.11 : "Extra parameters".

If enabled, the internal clock (CLKI) is automatically increased if AAC decoding needs a higher

clock. PS and SBR operation is automatically switched off if the internal clock is too slow for

correct decoding. Generally HE-AAC v2 ﬁles need 4.5× clock to decode both SBR and PS

content. This is why 3.5× + 1.0× clock is the recommended default.

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 10.5.4).

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

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