[M4IF Technotes] Re: 14496-3:2001 Corrigendum 2002

[Ralph Sperschneider]

menno wrote:
> Hi,
>
>
> >>Can anyone clarify why the "emphasis" field has been removed from the ADTS
> >>specification in 14496-3? This makes it impossible to decode
> >
> >older ADTS files
> >
> >>that comply with the standard before Corrigendum 2002.
> >>
> >>(and I'm not looking for this answer: "Because then it is the same as in
> >>13818-7 (MPEG-2 AAC)")
> >
> >the emphasis field found it´s way into the MPEG-4 ADTS
> >specification by failure.
> >Most likely, it was removed from the MPEG-2 AAC specification after
> >MPEG-4 was
> >branched (about 1996/97), and the MPEG-4 editors missed to remove
> >it as well.
> >This has now been fixed by the mentioned corrigendum.
>
>
> If that's what you call fixed. I think it's more broken now. How about the
> existing implementations? Isn't it better to just leave this mistake in than
> to break even more, after it has been in the standard for a few years already?

We considered this carefully. We however were not aware of any existing 
implementation. Furthermore, we expected that one would be curious about a data 
field with no semantic, which occurs in MPEG-4 but not in MPEG-2. However, no 
one in the standardization body could remember that someone has spoken up and 
asked for clarification. We hence assumed that no one had even noticed that this 
data field has been re-introduced in MPEG-4 by mistake. There was even no 
national body who expessed its concern during the ballot cycle, and there where 
no "No" votes on this corrigendum.
Subsequently we have to say sorry, but that is what happend.
Best regards,
Ralph
-- 
Dipl.-Ing. Ralph Sperschneider  | Phone: +49 9131 776 344
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