On Wed, Oct 26, 2011 at 12:36 AM, James <bjloc...@lockie.ca> wrote: > My signal strength is always above 0 but when I use -H, it is 0%. > Does that mean my signal strength is <0%? > Maybe femon should report 0.x%. > > $ femon > FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC) > status SCVYL | signal 00b9 | snr 00b9 | ber 00000000 | unc 00000000 | > FE_HAS_LOCK > > $ femon -H > FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC) > status SCVYL | signal 0% | snr 0% | ber 0 | unc 0 | FE_HAS_LOCK > > Is it normal to have <0% signal strength and still get reception?
For this demodulator, this is normal. The issue is there is no set standard for the way in which signal level and SNR are reported in the linux DVB API, and as a result there are numerous different formats. The format the s5h1409 demodulator driver delivers it doesn't match the demodulator that the person who wrote femon had available to him/her (the s5h1409 delivers both fields in 0.1dB increments, while whatever demod the femon author had to test with expected signal to be 0-65535 and SNR to be in 1/256 increments). In other words if you have an SNR of 30.0 dB, femon sees 0x012c, which it treats as a percentage of 0xffff which is 0.00457%, which gets rendered as 0%. Unfortunately, the driver community has never been able to form a consensus on how the data should be reported, so you cannot really argue the s5h1409 driver is "doing it wrong" (numerous other drivers report in the same manner as the s5h1409). You can read the mailing list archive for the gory history. It really is a fine example of the failure associated with "design by committee". Devin -- Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
