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Extend REC low bit rate bandwith options in Capture App till 75khz (#1380)

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* working_x32_Capture_till_75Khz

* format issues

* apply better accurate comments

* auto format issues
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Brumi-2021 2023-08-16 23:26:59 +02:00 • committed by GitHub
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6 changed files with 97 additions and 19 deletions
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20
firmware/common/oversample.hpp
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@ -40,17 +40,29 @@
* The baseband needs to know how to correctly decimate (or interpolate) so
* the set of allowed scalars is fixed (See OversampleRate enum).
* In testing, a minimum rate of 400kHz seems to the functional minimum.
*
* There are several different concepts or terms related to Capture and Replay,
* (1) oversampling (x8, x16 ,...) / decimation (/8, /16...)
* In Capture App , when ADC can not handle directly a requiered low sample rates ,
* we need to apply oversampling (x8. x16 ex) , getting more real samples than needed) by "x_number" ,
* and later to write it to SD card with the proper needed real sample rate , we apply Decimation , "/ number" .
*
* (2) up-sampling or re-escale or interpolation. (x8, x16, ...)
* In Replay-list App, when we got too low bit rate data for Hackrf ,
* we need to upsampling or interpolate or resampling to increase those low bit rates
* to a proper sample rate higher than the min. to be able to be transmitted by Hackrf.
*/
/* Gets the oversample rate for a given sample rate.
* The oversample rate is used to increase the sample rate to improve SNR and quality.
* This is also used as the interpolation rate when replaying captures. */
inline OversampleRate get_oversample_rate(uint32_t sample_rate) {
if (sample_rate < 50'000) return OversampleRate::x128; // 25kk..12k5, prepared for future, OVS ok, but decim. :128 still not implemented.
if (sample_rate < 100'000) return OversampleRate::x64; // 50k, prepared for future, OVS ok, but decim. :64 still not implemented.
if (sample_rate < 250'000) return OversampleRate::x16; // Now tentatively applied to 150k..100k - but as soon as we got decim :32, (150k x16, and 100k x32)
if (sample_rate < 50'000) return OversampleRate::x128; // 25k..12k5, prepared for future, OVS ok, but decim. x128 still not implemented.
if (sample_rate < 100'000) return OversampleRate::x64; // 50k, prepared for future, OVS ok, but decim. x64 still not implemented.
if (sample_rate < 150'000) return OversampleRate::x32; // 100k needs x32
if (sample_rate < 250'000) return OversampleRate::x16; // 150k needs x16
return OversampleRate::x8; // 250k .. 1Mhz, that decim :8 , is already applied.(OVS and decim OK)
return OversampleRate::x8; // 250k .. 1Mhz, that decim x8 , is already applied.(OVerSampling and decim OK)
}
/* Gets the actual sample rate for a given sample rate.