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Issue with Ittiam Codec running at a Sample Rate of 24000.

uschnerff
Prodigy 10 points

We are using the DM365 running with the Ittiam Codec. Our Audio is coming into the chip at a rate of 48K. Due to various performance issues, we cannot sample at 48K but instead have to set the Ittiam Codec to sample the audio at 24000.

What we have found is that any frequency above 12KHz is aliased back to a lower rate. For example 18KHz audio may come in a 6KHz.

Should this aliasing be occurring?

Is there any other setting that we can use that would prevent this from occurring?

 

  • 0
    TI__Mastermind 18130 points

    Hello uschnerff,

    Would you please copy your current settings here so we can evaluate what you are doing? I do not think that this is an issue with the codec as the codecs are not designed to do sample rate conversion. This is more likely a misconfiguration at the driver level.

    Have you tried running the arecord (which uses the ALSA driver) at a different frequency to see if the same behavior is experienced just to use as a test bench?

  • 0 in reply to TimHarron
    Prodigy 40 points

    Here are our current settings which are passed to AUDENC1_create()  (with name string "aaclc_enc"):


    ITTIAM_EAACPLUSENC_Params:
      s_iaudenc_params.size:                  112
      s_iaudenc_params.sampleRate:          24000
      s_iaudenc_params.bitRate:             96000
      s_iaudenc_params.channelMode:             1  (IAUDIO_2_0)
      s_iaudenc_params.dataEndianness:          2  (XDM_LE_16)
      s_iaudenc_params.encMode:                 0  (IAUDIO_CBR)
      s_iaudenc_params.inputFormat:             1  (IAUDIO_INTERLEAVED)
      s_iaudenc_params.inputBitsPerSample:     16
      s_iaudenc_params.maxBitRate:         576000
      s_iaudenc_params.dualMonoMode:            0
      s_iaudenc_params.crcFlag:                 0
      s_iaudenc_params.ancFlag:                 0
      s_iaudenc_params.lfeFlag:                 0
      noChannels:            2
      aacClassic:            1
      psEnable:              0
      dualMono:              0
      downmix:               0
      useSpeechConfig:       0
      invQuant:              2
      useTns:                1
      use_ADTS:              1
      use_ADIF:              0
      full_bandwidth:        0
      i_channels_mask:       0
      i_num_coupling_chan:               0
      fNoStereoPreprocessing:            0
      write_program_config_element:      0