Red Hat Bugzilla – Bug 810347
Incorrect sampling rate used for 300 baud AFSK
Last modified: 2015-02-17 09:12:30 EST
Description of problem:
Operation at 300 baud AFSK is rendered unusable by a faulty sampling rate selection algorithm in the AFSK modem (and possibly also by low quality filters for demodulation).
Version-Release number of selected component (if applicable):
soundmodem 0.16 (latest release) and probably all previous releases
Always: select AFSK at 300 baud (or in general bitrates lower than 1200 baud)
Steps to Reproduce:
AFSK modulation and demodulation at 300 baud should work properly as for higher bitrates such as 1200 baud.
It cannot (de/)modulate unless the first patch is applied. It might not demodulate properly unless the second patch is also applied (slightly more expensive in terms of CPU cycles).
It should (de/)modulate AFSK 300 baud properly.
A set of two patches is proposed until the original author manages to fix it:
- soundmodem-0.16-use-a-minimum-samplerate-for-afsk-v5.patch: fix for the sampling rate estimate;
- soundmodem-0.16-increase-rx-filters-parameters.patch: longer and more robust demodulator filters.
Created attachment 575492 [details]
Fix for the sampling rate estimate (AFSK)
Created attachment 575493 [details]
Optional patch to make the demodulator filters longer and more robust (AFSK)
The values might not be optimal. In particular they might not be optimal for all possible bit-rates (other than 300 baud) and all setups (e.g. different CPUs, soundcards and so on). However, the values in the patch should not cause an excessive expense in terms of CPU cycles on modern machines.
They have only been tested rather quickly on a SiS 7012 AC'97 audio controller.
As already explained in the comment, the two patches have not been extensively tested, therefore use it at your own risk.
This bug appears to have been reported against 'rawhide' during the Fedora 19 development cycle.
Changing version to '19'.
(As we did not run this process for some time, it could affect also pre-Fedora 19 development
cycle bugs. We are very sorry. It will help us with cleanup during Fedora 19 End Of Life. Thank you.)
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