Application

Clarkspur CD245X DSP series are originally designed for low cost Modem back in late 1980, and are consistently employed for low-end applications such as Audio related products successfully. This page describes about two such application examples recently programmed for the CD2458 DSP bench mark test. While many CD245x application chips are actually running at higher clock rate like 100MIPS and up with current process technologies, we developed these application programs assuming rather low MIPS operation so that we can utilize common FPGA chips instead of allocating big budget on wafer foundry service. Thanks to CD245x's small architecture, the CD245x series DSPs are fit for $20~$40 FPGA chips nowadays (As of Aug.2005). Current Clarkspur Flag Ship DSP series CD2470A,80A,90A would show about 50% better performance compare to the original CD245x series DSPs, although these application example programs are available only for CD245x at this time point.

MP3 Decoder

 

The MP3 decoder program running on the DEMO unit shown above complies ISO/IEC 11172-3 MP3 Layer-III, featuring. CD2458 24bit DSP was chosen for evaluation.

  • Bit rate: 32K,40K,48K,56K,64K,80K,96K,112K,128K,160K,192K,224K,256K,320Kbps, free format, Variable Bit Rate (VBR)
  • Sampling Frequency: 32KHz, 44.1KHz, 48KHz
  • Mode: Single ch., Dual ch., Stereo, Joint Stereo(intensity and/or MS stereo)

    •

    Resource requirement: MP3 ISO 11172-3
    Worst case MIPS (48KHz,320bps,JS) 26MIPS
    Data Memory (24bit/word) 12.5Kw*
    Program Memory (16bit/word) 20Kw


    * FPGA has only RAM memory on it. Some of the RAM area is filled with table data from the program memory data region at the beginning of the program. Actual RAM usage on the data memory is little less.

     

    Ogg Vorbis Decoder

    While many Audio fan end users as well as set manufacturers hate the confusion of the MP3,AAC license fee or usage charge emerged, one NPO has presented an audio compression program for free of charge. No license fee, no per use fee at all for anybody any application. This organization released its first version of such C program through Web as "Ogg Vorbis" on July,2002. (http://www.xiph.org/ogg) The technology is competitive with MP3 in performance, and said it complied no existing patent infringements. Since the algorithm is assuming a PC environment, it allows fairly big amount of RAM memory usage compare to MP3. Other than this problem, the algorithm seems quite friendly with most of audio application processors including CD245x series DSP.

  • Bit rate: Varies from 8Kbps to 500Kbps depending on the encoder parameters.
  • Sampling Frequency: 8KHz,11.025KHz, 12KHz, 16KHz, 22.1KHz, 24KHz, 32KHz, 44.1KHz, 48KHz
  • Mode: Single ch., Coupled and uncoupled stereo

    • Clarkspur has developed the "Ogg Vorbis" decoder on its time proven DSP CD2458 to get the following results.

    Resource requirement: Ogg Vorbis V1.0
    Worst case MIPS (48KHz,500Kbps,2ch.) 24MIPS
    Darta Memory (24bit/word) 43Kw*
    Program Memory (16bit/word) 25Kw*


    * FPGA has only RAM memory on it. Some of the RAM area is filled with table data from the program memory data region at the beginning of the program. Actual RAM usage on the data memory is little less. (Data RAM 35Kw + Data ROM 8Kw, and 10Kw program memory is an alternative selection for this case.)

    You can hear sample sounds decoded with our CD2458 DSP in various conditions. Please click on the icons below to hear them.

    44.1KHz sample, 105Kbps, Stereo
    16KHz sample, 27Kbps, Stereo
    8KHz sample, 11Kbps, Mono

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