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Original question:

CC2564C: cc2564c

CC2564C: cc2564c

Mani srinivas
Intellectual 300 points
Part Number: CC2564C


Hi Team,

Some phones have the CVSD codec which is at 8khz sampling rate (Motorola new version), so, In our product we have implemented for mSBC which is at 16 kHz SR. 

I'm trying to find specification details for CVSD, I didn't find anything (HFP 1.6 spec documentation)and even demo samples codes also there is no implementation for this.

Do you have any specification documentation or pdf for cvsd?

or  How to implement, any source code for this? 

  • 0
    TI__Mastermind 23525 points

    I'm told the details on the mSBC are found in the BT core spec, not the HFP spec.  I'll ask one of our engineers if he can point you directly there. 

    As far as demo and source code, we have a HFP demo that implements wideband speech example in our SDK:

    http://www.ti.com/tool/CC2564CMSP432BTBLESW

    The codec is implemented in our ServicePack FW on the controller.

    Regards,

    Travis

  • 0 in reply to tscheck
    Intellectual 300 points

    Hi Team,

    As I mentioned eariler some phone have CVSD codec while codec negotiation happens our product is failing there.

    Do you have any specification documentation or pdf for cvsd? where to find?

    Please let me know,Thank you

  • 0 in reply to Mani srinivas
    TI__Mastermind 27080 points

    Please refer to the, 'Audio' chapter of  BT core specs for CVSD codec details. 

    BLUETOOTH SPECIFICATION Version 5.0 | Vol 2, Part B page 494
    Baseband Specification
    9 AUDIO
    On the air-interface, either a 64 kb/s log PCM (Pulse Code Modulation) format
    (A-law or μ-law) may be used, or a 64 kb/s CVSD (Continuous Variable Slope
    Delta Modulation) may be used. The latter format applies an adaptive delta
    modulation algorithm with syllabic companding.
    The voice coding on the line interface is designed to have a quality equal to or
    better than the quality of 64 kb/s log PCM.
    Table 9.1 summarizes the voice coding schemes supported on the air
    interface. The appropriate voice coding scheme is selected after negotiations
    between the Link Managers.
    9.1 LOG PCM CODEC
    Since the synchronous logical transports on the air-interface can support a 64
    kb/s information stream, a 64 kb/s log PCM traffic can be used for
    transmission. Either A-law or μ-law compression may be applied. In the event
    that the line interface uses A-law and the air interface uses μ-law or vice versa,
    a conversion from A-law to μ-law shall be performed. The compression method
    shall follow ITU-T recommendations G. 711.
    9.2 CVSD CODEC
    A more robust format for voice over the air interface is delta modulation. This
    modulation scheme follows the waveform where the output bits indicate
    whether the prediction value is smaller or larger than the input waveform. To
    reduce slope overload effects, syllabic companding is applied: the step size is
    adapted according to the average signal slope. The input to the CVSD encoder
    shall be 64 ksamples/s linear PCM (typically 16 bits, but actual value is
    implementation specific). Block diagrams of the CVSD encoder and CVSD
    decoder are shown in Figure 9.1, Figure 9.2 and Figure 9.3. The system shall
    be clocked at 64 kHz.

    Thanks

  • 0 in reply to Hari Nagalla
    Intellectual 300 points

    Thank you  Hari,

    I shall go through that once.

    Any source code available for cvsd?

  • 0 in reply to Mani srinivas
    TI__Mastermind 27080 points

    Humm.. It is an already supported codec by the controller. So, it is surprising the codec negotiation is failing. Can, you provide BT snoop or air sniffer logs.

    Thanks