[Haskell-beginners] Problem reading sound data from mic with TChan

[Christopher Allen]

https://github.com/bitemyapp/blacktip/blob/master/src/Database/Blacktip.hs#L47-L54
:)

On Sun, Dec 20, 2015 at 7:38 PM, Luke Iannini <lukexipd at gmail.com> wrote:

> Hi Martin,
>
> On line 63 http://lpaste.net/147522#line63, when you do
>
> let sndChan = newTChan
>
>
> you're not actually creating a new TChan, but rather creating a reference to the STM action that creates new TChans.
>
>
> So this means that e.g. on line 71 http://lpaste.net/147522#line71, you are creating a new channel every time with
>
> ch <- sndChan
>
>
> Instead, you want to do:
>
> sndChan <- newTChanIO
>
> (or,
>
> sndChan <- atomically newTChan
>
> )
>
>
> And then pass that value to your other functions, which will just take TChan [Int32] rather than STM (TChan [Int32])
>
>
> Here's what I mean:
>
> http://lpaste.net/diff/147522/147557
>
>
> Hope that helps!
>
>
>
> On Sun, Dec 20, 2015 at 9:24 AM, Martin Vlk <martin at vlkk.cz> wrote:
>
>> Hi, I am working on a little toy project related to controlling graphics
>> display based on data from the computer microphone.
>>
>> I am basing the whole thing on concepts from game programming, so I have
>> a main loop which reads inputs, updates the world state and generates
>> outputs.
>>
>> As part of inputs there is microphone. I read data from it using the
>> pulse-simple library. The "simpleRead" function blocks if there is not
>> enough data available so I can't use it directly in the main loop or I
>> risk delays.
>>
>> So I figured I'll use a separate thread to read from the mic and write
>> data into a TChan. The main loop in separate thread then can read from
>> the TChan as needed and test for availability of data to avoid delaying
>> the main loop.
>>
>> Here is my current code: http://lpaste.net/147522
>>
>> The data is written into TChan in the "handleMic" function and read from
>> the TChan on line 85.
>>
>> The problem I have is that the TChan never seems to contain any data
>> when I read from it and that confuses me. Why?
>>
>> Does anyone see where is my problem?
>>
>> Many Thanks
>> Martin
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>>
>
>
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-- 
Chris Allen
Currently working on http://haskellbook.com
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