[Freeswitch-users] MP2

Steve Underwood steveu at coppice.org
Sat Jan 3 20:57:59 MSK 2015

Is there a standard set of test vectors for an MP2 decoder, and are they 
expected to give bit exact results?


On 01/04/2015 01:27 AM, Thomas Auge wrote:
> A very interesting tech demo, but from his own readme, it might not be suitable for a freeswitch module:
>    - imprecise: due to the integer-only implementation, many rounding errors will
>      occur; expect a 45-55 dB noise margin!
>    - slow: it implements the synthesis process from the spec, which is very slow
>      (82 multiplications, 1-2 divisions and countless shifts and additions per
>      sample!)
>    - not robust: it may easily crash on broken input data. Also, it ignores CRC
>      values completely.
>    - not thread-safe
> A bit of a bummer, because a lightweight decoder on top of twolame would have been nice.
> On 03.01.2015 13:51, Steve Underwood wrote:
>> I have no idea how well it works, but there is this MP2 decoder -
>> http://keyj.emphy.de/kjmp2/
>> On 01/03/2015 07:00 AM, Brian West wrote:
>>> That looks like just the encoder, so we would need both the encoder
>>> and decoder that takes signed linear.  I'll be on the look out for an
>>> option too.
>>> On Fri, Jan 2, 2015 at 4:54 PM, Thomas Auge <auge at virtues.net
>>> <mailto:auge at virtues.net>> wrote:
>>>       > G722 can be a native bearer capability on an ISDN b-channel but thats not widely used.  MP2 in your case is just
>>>       > establishing a data channel be it via ISDN or IP.
>>>       Yup. I'm fairly certain that's what FreeTDM does for G722, else it
>>>       wouldn't make much sense to have a codec
>>>       configuration option. :)
>>>       > Before proceeding I would seek out a license compatible
>>>       encoder/decoder library that can be used, MP2 can mean so many
>>>       > things their are multiple levels, options and details required
>>>       to properly implement it.  I highly suspect its not an
>>>       > afternoon event, I could be wrong if the right library is found
>>>       thats license compatible.
>>>       There are a couple, T(w/o)oLame comes to mind.
>>>       (http://www.twolame.org/ LGPL licensed) Any pointers as to which
>>>       capabilities are needed in such a library? It seems the libraries
>>>       are as outdated as the codec. :)

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