# Delay block controlled by input **URL:** \ **Category:** GNU Radio\ **Created:** [September 23, 2014, 8:39am UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174 "2014-09-23T08:39:53Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [September 23, 2014, 8:39am UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/1 "2014-09-23T08:39:53Z")
Hello, I have modified GNURadio delay block. It is a controlled delay from an input at runtime. I would like to know your opinion; if the block is well designed. > **[delay\_impl.cc - Pastebin.com](https://pastebin.com/f7Y24fin)** > > Pastebin.com is the number one paste tool since 2002. Pastebin is a website where you can store text online for a set period of time. > **[delay\_impl.h - Pastebin.com](https://pastebin.com/0gKDHgwL)** > > Pastebin.com is the number one paste tool since 2002. Pastebin is a website where you can store text online for a set period of time. ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [September 23, 2014, 3:01pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/2 "2014-09-23T15:01:54Z")
On Tue, Sep 23, 2014 at 2:38 AM, Carlos Alberto Ruiz Naranjo \< [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote: > [delay\_impl.h - Pastebin.com](http://pastebin.com/0gKDHgwL) What’s the use case for this? Specifically, how often do you need to update the delay and what’s the control mechanism? I ask because it feels like a message port would be more appropriate here than a streaming input. Tom ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [September 23, 2014, 3:03pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/3 "2014-09-23T15:03:46Z")
It simulates the signal delay of a satellite. It is updated every millisecond. The control mechanism is a block which calculates the satellite orbit every millisecond and measures the distance. 2014-09-23 14:54 GMT+02:00 Tom R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [September 23, 2014, 8:15pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/4 "2014-09-23T20:15:20Z")
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**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 7, 2014, 12:49pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/5 "2014-10-07T12:49:35Z")
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**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [September 23, 2014, 3:27pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/6 "2014-09-23T15:27:34Z")
* * * Discuss-gnuradio mailing list removed\_email\_address@domain.invalid [https://lists.gnu.org/mailman/listinfo/discuss-gnuradio](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 9:11am UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/7 "2014-10-08T09:11:31Z")
* * * Discuss-gnuradio mailing list removed\_email\_address@domain.invalid [https://lists.gnu.org/mailman/listinfo/discuss-gnuradio](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 7, 2014, 2:16pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/8 "2014-10-07T14:16:03Z")
Ok, you’ll have to explain why you’d need throttle, as this is almost never the case, especially not when a) working in a simulation or b) working with “real” hardware, as that usually enforces a sampling rate. If you know the physical sampling rate, counting samples _must_ work, unless your sampling clock drifts significantly, or you have _really_ fast moving satellites for which relativity is a concern at such low frequencies. Anyway, as an advisor told me once, if you want something done mathematically right, do it mathematically right (that was on the subject on simulating delay for radar targets): Transform your signal to frequency domain, multiply it with a complex sine of the frequency representing your time shift, and transform it back to time domain. This allows you (within numerical precision of the complex float and the length of your FFT) to have arbitrary accurate shifts, to dynamically update the frequency (depending on how you generate the complex sinusoid) and costs only moderately many ressources (OK, at roughly 10MS/s, this might still be relevant). Greetings, Marcus ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 12:30pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/9 "2014-10-08T12:30:08Z")
Sorry, I have explained bad: S I have the signal saved in a file and 10230000 samples are one second (in the real world). In the first graph I have two clocks (counters samples). When passing 102300 samples it increase 0.01 seconds. In the first watch this time controls the position of the satellite and his delay in this time. It allows to know what signal time is passing in the delay block. But I have a problem: clock 2 (a test clock) and clock 1 haven’t the same time; it has a drift. Then, I must use clock 2 ( count the samples in the delay block output, not input). But it creates a loop. 2014-10-08 12:07 GMT+02:00 Marcus Müller [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 12:08pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/10 "2014-10-08T12:08:31Z")
Hello Carlos, On 08.10.2014 09:10, Carlos Alberto Ruiz Naranjo wrote: > I generate the signal from a file (10230000 samples/s) to a file. My > sampling clock drifts significantly :S > No. Unless I misunderstood you, you have a big misconception: > “sampling clock” is _not_ the rate at which your samples pass through > your processing chain (ie. GNU Radio). It is the time base at which they > are measured, or simulated to, mathematically. > The device/software that actually captures the samples and saves them > has a fixed clock. If that clock changes too much a) compensate that in > software, if possible or b) get a better device. > This is digital signal processing. Real world time has _no_ meaning > here, everything is measured relative to the interval between two > sampling times. You can process the signal as fast or slow as you want > to (as long as that doesn’t lead to things like overflows), and nothing > in the processing chain should care. > > - Picture one: Counter Clock 2 is correct but Counter Clock 1 no. > Then I should use the second configuration, but it is not allowed because I > have a loop, right? > I don’t understand your graph, sorry ☹ Greetings, Marcus ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 1:20pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/11 "2014-10-08T13:20:21Z")
If you don’t have hardware involved, you have no ‘clock’. And as such, it can’t drift. M ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 1:34pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/12 "2014-10-08T13:34:23Z")
Yes, it is not a real time clock. This “clock” tracks the current time of the signal in GNURadio. clock2 and clock1 have a drift because the number of counted samples are different. For example, if it pass 10230000 samples the delay block is entering the delay in signal time = 1 second. 1 second in the real world (later I replay the signal with a USRP). 2014-10-08 13:18 GMT+02:00 Martin B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 1:22pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/13 "2014-10-08T13:22:41Z")
See also [http://gnuradio.org/redmine/projects/gnuradio/wiki/FAQ#What-does-sample-rate-mean-in-GNU-Radio](http://gnuradio.org/redmine/projects/gnuradio/wiki/FAQ#What-does-sample-rate-mean-in-GNU-Radio). M ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 1:41pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/14 "2014-10-08T13:41:23Z")
In that case, just use nitems\_read() [1] in your delay block to inherently calculate “simulated time”. However, I’m a bit curious about the effects of using delay to do this: Because, as long as the satellite is approaching you, you’re occasionally dropping samples, whereas you’re inserting zeros while it moves away from the observer. Unless your 10.23MHz signal contains only a oversampled signal you care about and then decimated after delay [2] this potentially really differs from what you’d be seeing in a real world receiver. Greetings, Marcus [1] [http://gnuradio.org/doc/doxygen/classgr\_1\_1block.html#a2279d1eb421203bc5b0f100a6d5dc263](http://gnuradio.org/doc/doxygen/classgr_1_1block.html#a2279d1eb421203bc5b0f100a6d5dc263) [2] in which case that kind of has a doppler-y touch to it… ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 1:44pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/15 "2014-10-08T13:44:18Z")
If you’re comparing real time (system clock) to your sample stream, you’ll get jitter, not drift, using a throttle. Throttle maintains a sample rate over time, but operates on blocks, and also is running under a non-realtime operating system. If you’re talking about drift between the clock on your receiver and the real world, that’s normal and you have to find ways to deal with it. - Jeff ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 2:39pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/16 "2014-10-08T14:39:48Z")
Delay Block is controlled by Satellite Orbit and Satellite Orbit by “simulated clock”. The output of Satellite Orbit is the delay (samples). Can I know the nitems\_read of Delay Block from other block (Satellite Orbit)? Maybe a solution is to introduce Orbit Satellite in Delay block, but this is really inefficient to do tests. And a problem if I want to change the Delay block for your solution (FFT). Really the delay is in the non-modulated signal. Jeff, it is a “simulated clock”. And it doesn’t run with throttle because the samples in the output of Delay block are different that the samples in the input. 2014-10-08 13:43 GMT+02:00 Jeff L. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 2:54pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/17 "2014-10-08T14:54:59Z")
Hi, On 08.10.2014 14:38, Carlos Alberto Ruiz Naranjo wrote: > Delay Block is controlled by Satellite Orbit and Satellite Orbit by > “simulated clock”. The output of Satellite Orbit is the delay (samples). > Can I know the nitems\_read of Delay Block from other block (Satellite > Orbit)? > Yes. It’s a public function, as you can see in the documentation I > linked. > > Maybe a solution is to introduce Orbit Satellite in Delay block, but this > is really inefficient to do tests. > Good point, but you should be able to test your “calculate transmission > delay from an integer” functionality externally; also, there’s no reason > to have something like a class “delay\_calculator”, with methods you call > from your modified delay block. You can test that very easily isolated. > And a problem if I want to change the > Delay block for your solution (FFT). > Well, yes, if you change approaches, the old approach will no longer > apply. That’s a design decision you’ll have to make. > Really the delay is in the non-modulated signal. > I don’t understand this sentence, sorry. Greetings, Marcus ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 3:10pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/18 "2014-10-08T15:10:10Z")
OK !! Thank you very much for the tips. Next week I will use it in my PC of the lab. 😉 The delay is in the data, not in the modulated signal. And I insert the average between the previous and the next sample. Greetings 2014-10-08 14:53 GMT+02:00 Marcus Müller [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 3:11pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/19 "2014-10-08T15:11:55Z")
And a question. In: uint64\_t [http://gnuradio.org/doc/doxygen/stdint\_8h.html#aec6fcb673ff035718c238c8c9d544c47](http://gnuradio.org/doc/doxygen/stdint_8h.html#aec6fcb673ff035718c238c8c9d544c47) gr::block::nitems\_read ( unsigned int _which\_input_) How I know wich\_input? 2014-10-08 15:08 GMT+02:00 Carlos Alberto Ruiz Naranjo \< removed\_email\_address@domain.invalid\>: ---
**Author:** ![Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/34f0e0/32.png) [@Carlos\_Alberto\_Ruiz](https://www.ruby-forum.com/u/Carlos_Alberto_Ruiz)\ **Post date:** [October 8, 2014, 3:25pm UTC](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174/20 "2014-10-08T15:25:57Z")
Really the question is: How can I call gr::block::nitems\_read (unsigned int _which\_input_) from a block to know the nitems\_read of another block? 2014-10-08 15:10 GMT+02:00 Carlos Alberto Ruiz Naranjo \< removed\_email\_address@domain.invalid\>: [Next page](https://www.ruby-forum.com/t/delay-block-controlled-by-input/232174.md?page=2)