VS1053B Datasheet, PDF (51/79 Pages) List of Unclassifed Manufacturers – Ogg Vorbis/MP3/AAC/WMA/MIDI AUDIO CODEC

VLSI
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VS1053b preliminary
VS1053B
9. OPERATION
Note: It is recommended that playback volume is decreased by e.g. 10 dB when fast forwarding/rewinding.
Note: Register DECODE TIME does not take jumps into account.
Note: Midi is not suitable for random-access. You can implement fast forward using the playSpeed
extra parameter to select 1-128× play speed. SCI DECODE TIME also speeds up. If necessary, rewind
can be implemented by restarting decoding of a MIDI file and fast playing to the appropriate place.
SCI DECODE TIME can be used to decide when the right place has been reached.
9.5.5 Maintaining Correct Decode Time
When fast forward and rewind operations are performed, there is no way to maintain correct decode time
for most files. However, WMA and Ogg Vorbis offer exact time information in the file. To use accurate
time information whenever possible, use the following algorithm:
1. Start sending an audio file to VS1053b.
2. Read extra parameter value pair positionMsec (Chapter 9.11).
3. If positionMsec is -1, show you estimation of decoding time using DECODE TIME (and your
estimate of file position if you have performed fast forward / rewind operations).
4. If positionMsec is not -1, use this time to show the exact position in the file.
Version 0.5, 2007-12-03
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