VS1053B Datasheet, PDF(59/79 Page) List of Unclassifed Manufacturers

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VS1053B Datasheet, PDF (59/79 Pages) List of Unclassifed Manufacturers – Ogg Vorbis/MP3/AAC/WMA/MIDI AUDIO CODEC

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VLSI

Solution y

VS1053b preliminary

VS1053B

9. OPERATION

positionMsec is a ï¬eld that gives the current play position in a ï¬le in milliseconds, regardless of

rewind and fast forward operations. The value is only available in codecs that can determine the play

position from the stream itself. Currently WMA and Ogg Vorbis provide this information. If the position

is unknown, this ï¬eld contains -1.

resync ï¬eld is used to force a resynchronization to the stream for WMA and AAC (ADIF, .mp4 / .m4a)

instead of ending the decode at ï¬rst error. This ï¬eld can be used to implement almost perfect fast forward

and rewind for WMA and AAC (ADIF, .mp4 / .m4a). The user should set this ï¬eld before performing

data seeks if they are not in packet or data block boundaries. The ï¬eld value tells how many tries are

allowed before giving up. The value 32767 gives inï¬nite tries.

The resync ï¬eld is set to 32767 after a reset to make resynchronization the default action, but it can be

cleared after reset to restore the old action. When resync is set, every ï¬le decode should always end as

described in Chapter 9.5.1.

Seek ï¬elds no longer exist. When resync is required, WMA and AAC codecs now enter broadcast/stream

mode where ï¬le size information is ignored. Also, the ï¬le size and sample size information of WAV

ï¬les are ignored when resync is non-zero. The user must use SM CANCEL or software reset to end

decoding.

Note: WAV, WMA, ADIF, and .mp4 / .m4a ï¬les begin with a metadata or header section, which must be

fully processed before any fast forward or rewind operation. SS DO NOT JUMP (in SCI STATUS) is

clear when the header information has been processed and jumps are allowed.

9.11.2 WMA

Parameter Address Usage

curPacketSize 0x1e2a/2b The size of the packet being processed

packetSize 0x1e2c/2d The packet size in ASF header

The ASF header packet size is available in packetSize. With this information and a packet start offset

from jumpPoints you can parse the packet headers and skip packets in ASF ï¬les.

WMA decoder can also increase the internal clock automatically when it detects that a ï¬le can not be de-

coded correctly with the current clock. The maximum allowed clock is conï¬gured with the SCI CLOCKF

Version 0.5, 2007-12-03

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