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Sample rate conversion (asynchronous SRC)

Dirk Buijsman
Expert 1070 points
Other Parts Discussed in Thread: SRC4184

I am looking for an optimized way to do Asynchronous Sample Rate Conversion on the C66xx architecture. There are various generic libraries available, like Secret Rabbit Code, but I am looking for something which is optimized for C66xx (we need to process many channels for a professional audio application, so 90dB down at the cut-off frequency). 

Does anybody know of an existing solution or have a suggestion on how to implement this effectively? My "planned approach" is to use an existing lib (SRC) written in C and swap out modules where I can with those from the DSPLIB (like cut-off filtering).

EDIT: It looks like Analog Devices offers a library for Blackfin. Does TI have something similar? If not, what is the recommended way of implementing this?

Thanks

  • 0
    TI__Guru*** 125430 points

    Dirk,

    Unfortunately I don't know of any readily available ASRC libraries from TI.  I believe you would either need a separate IC such as the SRC4184 or would need to license an algorithm from a 3rd party.

    Can you supply some more info about the signals, i.e. what sample rates, sample size, etc?

    Brad

  • 0 in reply to Brad Griffis
    Expert 1070 points

    Thanks for your reply Brad, any help is appreciated. 

    The audio input and autput clocks can be from different sources, so we can have a situation where the actual input clock is 47,995 Hz and the output clock 48,010 Hz. 

    The possible base-input rates are 8,000/16,000/22,050/32,000/44,100/48,000 and 96,000 Hz. The output rate is always 48,000 Hz. The goal is to be able to resample up to 128 streams in realtime on a 1GHz C66x DSP......

    Sample size can be 16 or 24 bits and possibly higher (I'll check).  This is for a professional audio application. The SCR algorithm should introduce as little phase distortion as possible and have a good cutoff (antialiasing) filter.

    The algorithms I have seen so far like SoX and Secret Rabbit Code seem perfectly adequate, but performance is critical considering the number of streams. For the antialiasing filter I believe I can use the FIR filter in DSPLIB, but ideally someone has implemented the whole chain before and we can use their code (through licensing/buying). 

    Are there any companies out there which might provide such a product? My alternative is as stated above: port an existing x86 lib to C66x, but this might be a lengthy process to get it up to the performance I require.

    EDIT: It looks like there is a resampling library for the C5000, but the implementation is a C66x incompatible lib and the library seems to have some limitations concerning performance tuning and input/output sampling rates.


    Thanks,

    Dirk

  • 0 in reply to Dirk Buijsman
    Intellectual 295 points

    Hi Dirk,

    Ittiam is a TI partner (www.ittima.com). We have the SRC that may meet your requirements. If you like, please send me your email address at (bob.lee@ittiam.com). I will send you the datasheet.

    Cheers,

    Bob 

  • 0 in reply to Bob Lee
    Expert 1070 points

    Thanks Bob! I sent you an Email. Would it be possible to share some information on performance on this forum for reference?

    Regards,

    Dirk