STA310 datasheet(19/90 Pages) STMICROELECTRONICS

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STA310

- Custom A (also named custom 0 in Dolby specifications),

- Custom D (also named custom 1 in Dolby specifications),

- Line mode,

- RF mode.

These modes refer to different implementation of the dialog normalization and dynamic range control features.

The mode is selected by programming the register COMP_MOD to the appropriate value.

Line Mode

In Line Mode (COMP_MOD = 2), the dialog normalization is always enabled. It is done by the decoder itself and

the dialog is reproduced at a constant level.

The dynamic range control variable encoded in the bitstream is used and can be scaled by the two scaling reg-

isters HDR (for high-level cut compression) and LDR (for low-level boost compression). In case of 2/0 downmix,

the high-level cut compression is not scalable.

RF Mode

In RF Mode (COMP_MOD=3), the dialog normalization is always performed by the decoder. The dialog is re-

produced at a constant level.

The dynamic range control and heavy compression variables encoded in the bitstream are used, but the com-

pression scaling is not allowed. This means that the HDR and LDR registers can not be used in this mode. A

+11dB gain shift is applied on the output channels.

Custom A Mode

In Custom A mode (COMP_MOD=0), the dialog normalization is not performed by the decoder and must be

done by another circuit externally.

The dynamic range control variable encoded in the bitstream is used and can be scaled by the two scaling reg-

isters HDR (for high-level cut compression) and LDR (for low-level boost compression).

Custom D Mode

In Custom D mode (COMP_MOD=1), the dialog normalization is performed by the decoder. The dynamic range

control variable encoded in the bitstream is used and can be scaled by the two scaling registers HDR (for high-

level cut compression) and LDR (for low-level boost compression).

4.6.1.2 Karaoke mode

The AC-3 decoder is karaoke aware and capable.

A karaoke bitstream can be composed of 5 channels: L for Left, R for Right, M for guide Melody, V1 for vocal

track 1 and V2 for Vocal track 2.

- When in karaoke aware mode, the channels L,R and M are reproduced, and the channels V1 and V2

are reproduced at a level fixed by the bitstream.

- When in karaoke capable mode, it is possible to choose to reproduce one, two or none of the two

incoming vocal tracks, V1 and V2.

The karaoke decoder is activated by the use of KARAMODE register, which specifies the downmix for the dif-

ferent modes. This register replaces DOWNMIX register. It is however possible to consider the incoming

karaoke channels as any other multichannel stream and output it with a downmix specified in DOWNMIX reg-

ister. For details, refer to the Digital Audio Compression AC-3 ATSC standard, annex C.

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