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LM49350: Digital mixer and playback speed control

Ricardo Li
Intellectual 1045 points
Part Number: LM49350
Other Parts Discussed in Thread: TLV320AIC3262

Dear teams,

Our customer is looking for a devices that could mix two digital signal to one, and he also want to control the playback speed and volume. The input interface could be I2S or PCM. The output signals are used to drive a speaker. In this application, there are two audio file. The customer want to mix them to one and adjust it's playback speed (fast forward or fast backward) and output volume.

I found LM49350 have digital mixer function, but it seems that it con't mix two I2S signal to one. It's first I2S used for ADC, and second I2S used for DAC.

I also noticed that TLV320AIC3262 could mix two I2S to one, and it also could adjust the volume. But I don't know, how to adjust the playback speed using TLV320AIC3262.

Do you have any idea? 

Thank you for your help in advance.

Regards

Ricardo

  • 0
    TI__Mastermind 30220 points

    Ricardo,

    I’m not sure what gave you the impression that the LM49350 can’t mix 2 i2s signals, it certainly can.  And if you would not be using the ADC or DAC you could mix the I2S lines and send them to one of the i2S outputs.  

    The speed control would need to be controlled by a processor of some kind.

    Best regards,

    -Steve Wilson

  • 0 in reply to Steve-Wilson
    TI__Intellectual 1045 points

    Hi Steve,

    Thank you for your help.

    The two I2S signal could be mixed to one and sent to DAC, then the analog signal could be used to drive headphone or loudspeaker. The config looks like this. Am I right?

    I'm not familiar with audio devices. If I want to control the playback speed using a processor, which parameter I need to adjust? Or do I need create a new audio file inside processor?

    Regards,

    Ricardo

  • 0 in reply to Ricardo Li
    TI__Mastermind 30220 points

    Ricardo,

    Your routing diagram is correct.  Keep in mind, if you are mixing two audio sources it may be wise to attenuate each of them to avoid distorting the digital mixer.  

    I've attached an updated Digital mixer diagram that might be a little easier to read.

    Regarding the playback speed,  this it out of my realm of expertise, and I imagine it will depend on the OS you are using,  there are likely audio libraries which would allow you to control the playback speed,  but that is just a guess on my part. 

    -Steve Wilson

    LM49352_Digital_Mixer.pdf

  • 0 in reply to Steve-Wilson
    TI__Intellectual 1045 points

    Steve,

    You answer is very useful. And thanks for your advice.

    Regards,

    Ricardo