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Original File Length (OFL) for mp3, mp3Pro, aac..., Gapless playback becomes possible.
Ivan Dimkovic
post Mar 24 2003, 19:17
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On AES 114th held in Amsterdam, Thomson Multimedia researchers presented a way to signal exact codec delay and file length in a backwards compatible fashion - in current mp3, mp3pro, aac, etc... coding algorithms. It is known as OFL - or Original File Length

Algorithm deals with non-exact file length and delays introduced by modern frequency-domain coding systems. Data for OFL is written in ancilliary data so it is completely backwards compatible - decoder without OFL will just ignore the OFL data.

OFL will allow gapless playback with OFL compatible decoders.

AES paper number is: 5830


PS: They are mentioning LAME in the paper smile.gif

This post has been edited by Ivan Dimkovic: Mar 24 2003, 19:26
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Ivan Dimkovic
post Mar 24 2003, 22:09
Post #2


Nero MPEG4 developer


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Posts: 1466
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QUOTE
Are you telling us that they published a paper just for this simple issue?


Well... maybe it is student work, I am not sure smile.gif

What is interesting is that they used three MP3 encoders in the table: FhG, FhG FastEnc and LAME 3.91 and showed their appropriate delays - inclusion of LAME in Thomson paper really surprised me, a good news indeed!

QUOTE
Well, at least we will have a uniform way to store delay.


I really hope they will publish this OFL specs (at least for MP3 and AAC)

There was also another good Dolby paper regarding new codec with variable frame length adjusted in a manner that it perfectly matches the video frame rate - but I guess this is for the new forum section (Scientific / Engineering discussion) smile.gif
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