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> > According to my ISO doc (section 2.4.2.3), for layer III, decoders are not
> required to support higher free format higher than 320kbps. So free format
> is not restricted to <=320kbps.
> > And decoders must support free format at least up to 320k.
>
> My ISO 13818-3 documentation : Section 2.4.2.3
> "The decoder is not required to support bitrates higher than 256 kbit/s, 160
> kbit/s, 160 kbit/s in respect to Layer I, II and III when in free format
> mode."
>
> And in 2.1.74 : "2.1.74 free format [audio]: Any bitrate other than the
> defined bitrates that is less than the maximum valid bitrate for each
> layer."
>
> So, there is a maximum bitrate for free format or my ISO documentation is
> diferent from the original ISO or there's a newer version of the doc.
> My ISO 13818-3 is from 11/11/99 , and have 634 kb (doc format).
>
> There is any document that modify the ISO 13818-3 ??
>
As Gaby pointed out, it says the "decoder is not requires to support..."
which doesnt say they are invalid MP3 files :-)
It's kind of a moot point right now, since it seems like
all but one of the software enocoder out there support
any kind of free format.
ISO 13818 is the MPEG2 spec. MPEG2 only supports fixed bitrates
up to 160kbs, so it is interesting that MPEG2 free format is
required to go up to 256kbs. At 16khz, this bitrate would produce
an mp3 file the same size as the input .wav file :-)
My MPEG1 doc (ISO 11172-3,purchased from the ISO) says decoder must
support free format up to 320kbs. 320kbs is also the number given in
Fraunhofer's "MPEG Layer3 Bitstream Syntax and Decoding"
documentation.
Mark
--
MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
