# How to send envelope values to IVMeterControl

**URL:** <https://iplug2.discourse.group/t/how-to-send-envelope-values-to-ivmetercontrol/334>\
**Category:** Uncategorized\
**Created:** [6 March 2021 18:17 UTC](https://iplug2.discourse.group/t/how-to-send-envelope-values-to-ivmetercontrol/334 "2021-03-06T18:17:15Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![ShellyMinks](https://avatars.discourse-cdn.com/v4/letter/s/8e7dd6/32.png) [@ShellyMinks](https://iplug2.discourse.group/u/ShellyMinks)\
**Post date:** [6 March 2021 18:17 UTC](https://iplug2.discourse.group/t/how-to-send-envelope-values-to-ivmetercontrol/334/1 "2021-03-06T18:17:15Z")

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Hi, I’ll be very thankful if anyone can help me.

In my plugin, I’m calculating the envelope of the inputs. And I want the user to be able to visualize the envelope, the input, and the output of the plugin in a meter (I’m using IVMeterControl). I’ve created the input and output meters with `IPeakSender`, and I’m trying to create the envelope meter with `IBufferSender`. However, I’m having trouble writing the input parameter of `ProcessBlock()` for the `IBufferSender`.

Please tell me what I’m doing wrong or if there’s a better way to create a meter for a value that is calculated while processing the audio:

```
  void MyPlugin::OnIdle()
  {
    mMeterInSender.TransmitData(*this);
    mMeterOutSender.TransmitData(*this);
    mMeterEnvSender.TransmitData(*this);
  }    

void MyPlugin::ProcessBlock(sample * *inputs, sample * *outputs, int nFrames
{
  sample\*\* senv; //Initializing sample for the envelope data        
  for (int s = 0; s < nFrames; s++) { 
      env= XXXXXX; //calculate envelope
      senv[0][s] = env; //update senv with envelope value 
       
      outputs[0][s] =XXX; //update outputs
      outputs[1][s] = XXX;
    }
  mMeterInSender.ProcessBlock(inputs, nFrames, kMeterIn);
  mMeterEnvSender.ProcessBlock(senv, nFrames, kMeterEnv);
  mMeterOutSender.ProcessBlock(outputs, nFrames, kMeterOut);
}

```

And in my header file:

```
private:
  IPeakSender<1> mMeterInSender;
  IPeakSender<1> mMeterOutSender;
  IBufferSender<1> mMeterEnvSender;

```

I can tell that I’m initializing `sample** senv ` wrong but I can’t tell how to do it right.  
I’m sorry if it’s a noob question but I’ve been looking through the forums and googling a lot and I just can’t figure it out. I get kinda confused around pointers…

Thanks!

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**Author:** ![olilarkin](https://yyz2.discourse-cdn.com/free1/user_avatar/iplug2.discourse.group/olilarkin/32/2_2.png) [@olilarkin](https://iplug2.discourse.group/u/olilarkin)\
**Post date:** [6 March 2021 20:07 UTC](https://iplug2.discourse.group/t/how-to-send-envelope-values-to-ivmetercontrol/334/2 "2021-03-06T20:07:53Z")

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If you are going to use an IPeakSender or IBufferSender which have `ProcessBlock(sample** inputs, ...)` style methods, then you need to keep a “scratch buffer”, some memory that is big enough to contain nFrames worth of sample values output by the envelope generator. [Here](https://gist.github.com/olilarkin/1103fb82de3ace6d4c94660d534100d9) is an example of how I do that using some WDL classes, but you can also do it with, e.g std::vector.

However, you probably don’t need to send buffers of samples if you are visualizing the envelope. The UI refresh rate is only 60 times per second which is a lot slower than the sample rate. You can probably get away with sending a single value per block. I would use an ISender and just push the last value returned by the envelope, once per block,

> <https://github.com/iPlug2/iPlug2/blob/master/Examples/IPlugInstrument/IPlugInstrument.cpp#L97>

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<div class="post-metadata">

**Author:** ![olilarkin](https://yyz2.discourse-cdn.com/free1/user_avatar/iplug2.discourse.group/olilarkin/32/2_2.png) [@olilarkin](https://iplug2.discourse.group/u/olilarkin)\
**Post date:** [6 March 2021 21:18 UTC](https://iplug2.discourse.group/t/how-to-send-envelope-values-to-ivmetercontrol/334/3 "2021-03-06T21:18:47Z")

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You can also do it without a queue, like in this example

> <https://gist.github.com/olilarkin/5fddce683cf31e75ad93855f55841c76>

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<div class="post-metadata">

**Author:** ![ShellyMinks](https://avatars.discourse-cdn.com/v4/letter/s/8e7dd6/32.png) [@ShellyMinks](https://iplug2.discourse.group/u/ShellyMinks)\
**Post date:** [8 March 2021 23:50 UTC](https://iplug2.discourse.group/t/how-to-send-envelope-values-to-ivmetercontrol/334/4 "2021-03-08T23:50:19Z")

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Used this one and it worked perfectly! Thank you so much!