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What kind of audio output format on playback dust.aac?

Tai Chang
Intellectual 740 points

Hi all,

use demo decode program to decode data/sound/dust.aac or dust.g711 file.

I would like to know the DM6467 output format? I2S or others ???

 Thanks !!

 

Tai Chang.

  • 0
    TI__Mastermind 37340 points

    Tai,

    I would like to break this down into two parts. 

    The first (which I like to think of as the software side) is decoding, which means taking a compressed stream (acc, g.711,...) and applying decoder process to come up with a PCM stream.

    The second (which I like to think of as the hardware aspect) is how you transfer this decoded PCM stream to the audio output interface of the chip (the actual pins on the chip)...DM6467 supports McASP bus for audio; if you refer to McASP user's guide (http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=spruer1b), you will see that this bus has the ability to support I2S, SPDIF... among other formats.  Therefore, we do support I2S and others

    I hope this helps.

  • 0 in reply to Juan Gonzales
    Intellectual 740 points

    Hi Juan,

    I have read this doc and knew the TDM output interface, it does support I2S when the data slot was set to 2.

    I measured the output pin of DM6467: MCASP0_ACLKX=1.536MHz, and MCASP0_AFSX=48KHz,

    According to these 2 pins, can we tell the TDM outputs I2S format mode ?  

     

    Thanks,

     

    Tai Chang

  • 0 in reply to Tai Chang
    TI__Mastermind 37340 points

    You would also need to know the bits per channel and how many channels.  For example, in the above example, if we knew this was for one channel of audio with 32-bits per channel, we would be able to determine ACLKX

         ACLKX should equal = (1 channel) x ( 32-bits per channel) x 48 KHz = 1.536 MHz.

    Since this is what we see at MCASP0_ACLKX pin, we can have some level of assurance that we are using I2S.

  • 0 in reply to Juan Gonzales
    Intellectual 740 points

    Hi Juan,

    Here you mean one channel is L or R channel or both L,R channel ?

    Note:

    I use VLC player to play dust.aac file, it shows 2ch & 48KHz.

    Thanks,

    Tai Chang.

     

  • 0 in reply to Tai Chang
    TI__Mastermind 37340 points

    Tai,

    I meant one 32-bit channel as in left OR right; although alternatively, you could be supporting 2 16-bit channels.  This is why I think we need to know not only the number of channels but the bits per channel.

  • 0 in reply to Juan Gonzales
    Intellectual 740 points

    Dear Juan,

    I found something interesting.

    The MCASP0_ACLKX pin output 1.5MHz in playing back dust.aac file, but I play the same file with VLC player on PC via HDMI output, the Bclk is 3 MHz.

    That means the DM6467 only output 16bits per channel but it should be 32bits per channel.

    I can not  find the setting where to modify to make the MCASP0_ACLKX pin output 3MHz.

    Can you help me?

     

    Thanks,

    Tai Chang