Stressing "average rate"! In GNU Radio, samples are processed in as much space there's output buffer and/or how many samples a block wants to consume or produce at once.
In the case of throttle, a single call to its work() method takes all the input there is (let's say it's 8000 samples in this round; the value depends on how the flow graph operates, and can and will change from iteration to iteration!), copies it to the output buffer (the sync_block idiom in GNU Radio ensures that there's always at least as much output space available as input, so the min(input available, output space available) is handed to the work() function), and then just waits as long as it needs to wait: simply n_samples_copied * sampling_rate. That means that if you set the sampling rate to 1, the throttle will block execution for 8000s, and then the downstream block will be informed that there are 8000 new items to be processed. A common misconception is that setting a sampling rate would make throttle emit 1 sample every 1/sampling rate, which is not the case. This, by the way, is the reason why it's *always* bad to have a throttle block connected to some hardware sink, even if the hardware sink's sampling rate is lower than the throttle's rate; the "chunky" nature of passing samples makes it likely that the samples simply don't reach the hardware sink in time. Best regards, Marcus On 23.07.2016 03:51, Martin Braun wrote: > On 07/22/2016 04:38 PM, Lakshay Narula wrote: >> Thanks Martin, that was exactly what I was looking for. >> >> Would the following statement be correct: the GNU Radio flowgraph always >> produces samples as fast as the CPU can (irrespective of the set sample >> rate or throttle), and stops producing whenever the USRP sink buffer is >> full. > Yup. > >> Also, does the throttle block work in a similar fashion? > That block blocks work() such that the average rate through it is what > it's set to to. > > M >> Thanks again, >> Lakshay. > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
