# Stream ID in virtual source Block

**URL:** <https://www.ruby-forum.com/t/stream-id-in-virtual-source-block/242184>\
**Category:** GNU Radio\
**Created:** [June 3, 2015, 11:30am UTC](https://www.ruby-forum.com/t/stream-id-in-virtual-source-block/242184 "2015-06-03T11:30:22Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [June 3, 2015, 11:30am UTC](https://www.ruby-forum.com/t/stream-id-in-virtual-source-block/242184/1 "2015-06-03T11:30:22Z")

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Hii  
What should i input in the “stream ID” field of Virtual Source block?

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**Author:** ![monika\_bansal](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7c8e57/32.png) [@monika\_bansal](https://www.ruby-forum.com/u/monika_bansal)\
**Post date:** [June 3, 2015, 11:54am UTC](https://www.ruby-forum.com/t/stream-id-in-virtual-source-block/242184/2 "2015-06-03T11:54:19Z")

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That’s totally up to you – any text that you can remember.  
You’d put the same value into the Virtual Sink block’s stream ID, so  
that they are connected.

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**Author:** ![monika\_bansal](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7c8e57/32.png) [@monika\_bansal](https://www.ruby-forum.com/u/monika_bansal)\
**Post date:** [June 3, 2015, 11:57am UTC](https://www.ruby-forum.com/t/stream-id-in-virtual-source-block/242184/3 "2015-06-03T11:57:50Z")

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Thanks Marcus …

On Wed, Jun 3, 2015 at 3:23 PM, Marcus Müller [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)

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**Author:** ![monika\_bansal](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7c8e57/32.png) [@monika\_bansal](https://www.ruby-forum.com/u/monika_bansal)\
**Post date:** [June 3, 2015, 2:19pm UTC](https://www.ruby-forum.com/t/stream-id-in-virtual-source-block/242184/4 "2015-06-03T14:19:14Z")

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That’s because you made a loop, and that’s illegal; why do you feed the  
output of the OFDM CP back into the carrier allocator?

Best regards,  
Marcus

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**Author:** ![monika\_bansal](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7c8e57/32.png) [@monika\_bansal](https://www.ruby-forum.com/u/monika_bansal)\
**Post date:** [June 3, 2015, 12:38pm UTC](https://www.ruby-forum.com/t/stream-id-in-virtual-source-block/242184/5 "2015-06-03T12:38:09Z")

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hii  
i made the following Flowgraph :

Virtual Source -----\> OFDM Carrier allocator --------\> FFT -------\> OFDM  
Cyclic Prefixer -----\> Virtual Sink

When i am executing the flowgraph it says – "runtime error : flowgraph  
has  
loops ! ".  
What should i do ?

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<div class="post-metadata">

**Author:** ![monika\_bansal](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7c8e57/32.png) [@monika\_bansal](https://www.ruby-forum.com/u/monika_bansal)\
**Post date:** [June 4, 2015, 4:50am UTC](https://www.ruby-forum.com/t/stream-id-in-virtual-source-block/242184/6 "2015-06-04T04:50:17Z")

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Thanks…  
i got it.

On Wed, Jun 3, 2015 at 7:08 PM, Francisco A.  
\<removed\_email\_address@domain.invalid

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**Author:** ![monika\_bansal](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7c8e57/32.png) [@monika\_bansal](https://www.ruby-forum.com/u/monika_bansal)\
**Post date:** [June 3, 2015, 3:39pm UTC](https://www.ruby-forum.com/t/stream-id-in-virtual-source-block/242184/7 "2015-06-03T15:39:52Z")

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Hi Monika.

Remember that the Virtual Source’s output is just the input of the  
Virtual Sink with the same ID.

It is a convenient way of making a nicer and tidier graph without so  
many “wires”.

I use them also as a “signal copier”:

(something X) —\> Virtual Sink ID 1

Virtual Source ID 1 ----\> one copy of X  
-----\> another copy of X  
------\> etc  
[…]  
------\> etc

This way I don’t have to remake all the connections when I change X.

Bye.

2015-06-03 9:18 GMT-03:00 Marcus Müller [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):