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Topic: Filter Coefficients in ATRAC? (Read 3567 times) previous topic - next topic

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  • pat
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Filter Coefficients in ATRAC?
Since there is a standard filter coefficients given in mp3(ISO 11172-3), I wonder if there is a standard filter coefficients I can find for ATRAC?

If there is no, how do i go about deciding the coefficients i'm going to use to build the ATRAC encoder?

  • Gabriel
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Filter Coefficients in ATRAC?
Reply #1
Do you have the specifications of the Atrac format?

  • pat
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Filter Coefficients in ATRAC?
Reply #2
No. I don't have something as detailed like the ISO 11172. So far I only have the overall block diagrams, without the detailed coefficients.

I only know the QMF have to divide the input signal into 3 subbands, 0 - 5.5kHz, 5.5 - 11kHz, and 11 - 22kHz.

  • Gabriel
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Filter Coefficients in ATRAC?
Reply #3
So how could you be able to write an encoder without specifications or reference source code?

  • pat
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Filter Coefficients in ATRAC?
Reply #4
Hm.....that's my problem. I'm actually doing this as my project for part of my coursework.....

Is there anyone who is familiar with ATRAC? I sincerely need help.....

  • Gabriel
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Filter Coefficients in ATRAC?
Reply #5
The problem is that we do not have access to Atrac specifications (perhaps you have them), so most of us are unable to help you on this matter.

  • wkwai
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Filter Coefficients in ATRAC?
Reply #6
Sony guards its commercial secrets very well.... No doubt that without the proper specs, you can't implement an ATRAC coder/decoder.. Even the huffman tables are unique.. even if it does not mention any specific quantization algorithm..

  • menno
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Filter Coefficients in ATRAC?
Reply #7
Filters are not really the problem. If you know the subband edges you can easily design them yourself 
Try searching for a book/paper on subband filter design.

BTW: I think ATRAC does 2 filterbanks. One that splits the signal in 2 subbands (0-11,11-22) and one that splits the first subband in 2 more (0-5.5,5.5-11). You can do the second filterbank by decimating the prototype filter of the first by 2. This leaves you to design just a prototype filter for the first filterbank that has only 2 subbands (so splitting signal in halve). This is the easiest filterbank possible 

Menno

  • pat
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Filter Coefficients in ATRAC?
Reply #8
Thanks guys. Think I still manage to handle the filter. But then when come to the Bit Allocation and the Spectral Quantization parts, i become more n more headache. As what Gabriel said, Sony guides their technology tightly that I couldn't find any of the standards carry on with my work. So i am kinda stuck now.

Does anyone can help me out????

  • wkwai
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Filter Coefficients in ATRAC?
Reply #9
Quote
Filters are not really the problem. If you know the subband edges you can easily design them yourself 
Try searching for a book/paper on subband filter design.


I think it is not as simple as that.. The reconstruction subband filterbanks MUST match the analysis subband filterbanks, otherwise, there could be aliasing artifacts in the decoded audio data..