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List:       xine-codec-devel
Subject:    Re: [codec-devel] QDMC progress
From:       Benjamin Larsson <banan () student ! luth ! se>
Date:       2003-12-16 1:04:57
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Sascha Sommer wrote:

>>Hi,
>>
>>Sorry for the late answer.
>>
>>    
>>
>>>They are up at:
>>>
>>>http://tranquillity.campus.luth.se/~banan/qdmc/
>>>      
>>>
>>thx
>>
>>    
>>
>>>And when I got some attention, when using the qt stuff in mplayer,
>>>does mplayer pass samplerate to the decoder ?
>>>      
>>>
>>Yes, see libmpcodecs/ad_qtaudio.c
>>    
>>
>
>Some more info about QDMC.
>According to http://www.scout.chuvashia.com/faqvqf.htm
>and http://www.rjamorim.com/rrw/qdmc.html
>QDMC is based on LBpack by Dmitry Shmunk.
>Players for dos and windows can be found at
>ftp://ftp.simtel.net/pub/simtelnet/msdos/sound/lbit157.zip
>It would be interesting to know how different the codecs are.
>

Very intresting information, and by reading the history one can find this:

      - player now is 1.5 times faster (radix-4 FFT implementation)
      - packer is about 1.3 times faster (radix-4 FFT implementation)

this seams to be the only information I could find about the Low Bitrate 
codec
that LBpack stands for. My guess is that the (i)FFT is used for 
resynthesis of the 
<http://iccb.med.harvard.edu/chemistry/resynthesis_platform.htm>
sound. This is also the only(!) information I could dig up on this 
algorithm from google and groups. The use of this form of reconstruction 
may answer why the frequency sweep from my pdf is so noisy. The QDM 
codec is "bleeding" quite much in comparision to mp2 and mp3.

/Benjamin


<http://iccb.med.harvard.edu/chemistry/resynthesis_platform.htm>

>
>Sascha
>
>
>
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