VS1033 Datasheet, PDF(49/70 Page) List of Unclassifed Manufacturers

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

VS1033 Datasheet, PDF (49/70 Pages) List of Unclassifed Manufacturers – MP3/AAC/WMA/MIDI AUDIO CODEC

◁

VLSI

Solution y

VS1033a PRELIMINARY

VS1033A

9. OPERATION

9.9 Fast Forward / Rewind

9.9.1 MP3

MPEG1.0 and MPEG2.0 layer 3 deï¬nes a stream format suitable for random-access. When you want to

skip forward or backwards in the ï¬le, ï¬rst send 2048 zeros, then continue sending the ï¬le from the new

location.

By sending zeros you make certain a partial frame does not cause loud artefacts in the sound. The normal

ï¬le type checking then ï¬nds a new MP3 header and continues decoding.

9.9.2 AAC - ADTS

MPEG2.0 Advanced Audio Coded (AAC) deï¬nes a stream format suitable for random-access (ADTS).

When you want to skip forward or backwards in the ï¬le, ï¬rst send 2048 zeros, then continue sending the

ï¬le from the new location.

By sending zeros you make certain a partial frame does not cause loud artefacts in the sound. The normal

ï¬le type checking then ï¬nds a new ADTS header and continues decoding.

9.9.3 AAC - ADIF, MP4

MPEG4.0 Advanced Audio Codec (AAC) speciï¬es a multimedia ï¬le format (.mp4 / .m4a) but does not

specify a stream format and MPEG2.0 AAC speciï¬es a ï¬le format (ADIF) in addition to the streamable

ADTS format. ADIF and .mp4 / .m4a are not suitable for random-access and it is recommended that

they are converted to ADTS format for playback.

However, it is also possible to implement fast forward and rewind for ADIF and .mp4 / .m4a ï¬les. The

easiest way is to use the resync ï¬eld (see section 9.8.1):

â¢ Write 8192 to resync

â Write 0x1969 to SCI WRAMADDR, Write 0x2000 to SCI WRAM

â¢ Send 2048 zeroes

â¢ Make a seek X in the ï¬le (X > 0 for forward seek)

â¢ Indicate the low part of the seek amount by writing to seek1

â Write 0x1967 to SCI WRAMADDR, Write (X â 2048)&1023 to SCI WRAM

â¢ Indicate the high part of the seek amount by writing to seek2

â Write 0x1968 to SCI WRAMADDR, Write (X â 2048)/1024 to SCI WRAM

â¢ Continue sending the ï¬le from the new location

Perfect fast forward and rewind can be implemented by using the jumpPoints table and making seeks

only on packet or data block boundaries.

Version 0.6, 2005-01-05

▷