Resizing of sample FIFO in output plugins: updated documentation

plugins/samplesink/bladerfoutput/readme.md

@@ -27,6 +27,16 @@ Device start / stop button.
 <h3>2: Baseband sample rate</h3>
 
 This is the baseband sample rate in kS/s before interpolation (4) to produce the final stream that is sent to the BladeRF device. Thus this is the device sample rate (6) divided by the interpolation factor (4).
+
+Transmission latency depends essentially in the delay in the sample FIFO. The FIFO size is calculated as follows:
+
+For interpolation by 32 the size is fixed at 150000 samples, Delay is 150000 / B where B is the baseband sample rate. Below is the delay in seconds vs baseband sample rate in kS/s from 48 to 500 kS/s:
+
+![BladeRF output plugin FIFO delay 32](../../../doc/img/BladeRFOutput_plugin_fifodly_32.png)
+
+For lower interpolation rates the size is calculated to give a fixed delay of 250 ms or 75000 samples whichever is bigger. Below is the delay in seconds vs baseband sample rate in kS/s from 48 to 400 kS/s. The 250 ms delay is reached at 300 kS/s:
+
+![BladeRF output plugin FIFO delay other](../../../doc/img/BladeRFOutput_plugin_fifodly_other.png) 
   
 <h3>3: Frequency</h3>
 

plugins/samplesink/hackrfoutput/readme.md

@@ -29,6 +29,10 @@ The settings on Tx or Rx tab are reapplied on start so these settings can be con
 <h3>2: Baseband sample rate</h3>
 
 This is the baseband sample rate in kS/s before interpolation (5) to produce the final stream that is sent to the HackRF device. Thus this is the device sample rate (8) divided by the interpolation factor (5).
+
+Transmission latency depends essentially in the delay in the sample FIFO. The size of sample FIFO is calculated to give a fixed delay of 250 ms or 150000 samples whichever is bigger. Below is the delay in seconds vs baseband sample rate in kS/s from 48 to 800 kS/s. The 250 ms delay is reached at 600 kS/s:
+
+![BladeRF output plugin FIFO delay other](../../../doc/img/HackRFOutput_plugin_fifodly.png) 
   
 <h3>3: Frequency</h3>
 

plugins/samplesink/limesdroutput/readme.md

@@ -48,7 +48,11 @@ This is the sample rate at which the DAC runs in kS/s (k) or MS/s (M) after hard
 <h3>2B: Baseband sample rate</h3>
 
 This is the baseband sample rate in kS/s before interpolation (9) to produce the final stream that is sent to the LimeSDR device. Thus this is the host to device sample rate (10) divided by the software interpolation factor (9).
-  
+
+Transmission latency depends essentially in the delay in the sample FIFO. The size of sample FIFO is calculated to give a fixed delay of 250 ms or 48000 samples whichever is bigger. Below is the delay in seconds vs baseband sample rate in kS/s from 48 to 250 kS/s. The 250 ms delay is reached at 192 kS/s:
+
+![BladeRF output plugin FIFO delay other](../../../doc/img/LimeSDROutput_plugin_fifodly.png) 
+
 <h3>3: Center frequency</h3>
 
 This is the center frequency of transmission in kHz.