ISO 11172-3, dist10

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ISO 11172-3, dist10

Torsten Mohr
Hello,

i just bought the ISO11172-3 and also downloaded the package dist10.

I have some questions now and it would be great if anybody could give
me some hints on them.  I hope they are not off-topic.  The questions
are related to ISO11172-3 and/or dist10.  If my questions are off-topic
here, could anybody please give me some hint where my questions are
better placed?

I stumbled across some differences in chapter 2.4.1.7 (decoding)
where "dist10" does not decode main_data() as described in
ISO-11172-3.  I wonder where this difference comes from and to
which one i should comply.

One more thing is the CRC, in dist10 the CRC is applied to the single
bits of the header and so on.  Can i just calculate the CRC over all
data in the frame (except the two bytes of the CRC in the header)?

Are there some test MP3-data available for decoders?  Some data that
i can use to test if a decoder complies to MP3?


Thanks for any hints,
Torsten.
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Re: ISO 11172-3, dist10

Ruckert Martin
Dear Torsten,


> I stumbled across some differences in chapter 2.4.1.7 (decoding)
> where "dist10" does not decode main_data() as described in
> ISO-11172-3.  I wonder where this difference comes from and to
> which one i should comply.

As far as I know, dist10 does comply exactly with ISO 2.4.1.7
May be you could describe in some more detail where you see the differences.

> One more thing is the CRC, in dist10 the CRC is applied to the single
> bits of the header and so on.  Can i just calculate the CRC over all
> data in the frame (except the two bytes of the CRC in the header)?

The CRC is computed only for the "important" bits. This saves time in computing
and checking the crc. Which bits are important is given in detail in the standard.

> Are there some test MP3-data available for decoders?  Some data that
> i can use to test if a decoder complies to MP3?

There is some test data, that can be used to check some aspects of decoding mp3,
mainly numerical accuracy. These tests are freely available on the net and
are described in iso 11172-4 part 4 compliance checking. (There is little
use in buying part 4 of the standard, get it from a library.)

Yours
    Martin Ruckert


-------------------------------------
Prof.Dr.Martin Ruckert
Munich University of Applied Sciences
FB07 Mathematics and Computer Science
Lothstrasse 34
D-80335 Munich
GERMANY
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