On Thu, Oct 22, 2009 at 3:13 PM, Jean Delvare <khali@xxxxxxxxxxxx> wrote: > Hi folks, > > I am looking for details regarding the DVB frontend API. I've read > linux-dvb-api-1.0.0.pdf, it roughly explains what the FE_READ_BER, > FE_READ_SNR, FE_READ_SIGNAL_STRENGTH and FE_READ_UNCORRECTED_BLOCKS > commands return, however it does not give any information about how the > returned values should be interpreted (or, seen from the other end, how > the frontend kernel drivers should encode these values.) If there > documentation available that would explain this? > > For example, the signal strength. All I know so far is that this is a > 16-bit value. But then what? Do greater values represent stronger > signal or weaker signal? Are 0x0000 and 0xffff special values? Is the > returned value meaningful even when FE_HAS_SIGNAL is 0? When > FE_HAS_LOCK is 0? Is the scale linear, or do some values have > well-defined meanings, or is it arbitrary and each driver can have its > own scale? What are the typical use cases by user-space application for > this value? > > That's the kind of details I'd like to know, not only for the signal > strength, but also for the SNR, BER and UB. Without this information, > it seems a little difficult to have consistent frontend drivers. > > Thanks, > -- > Jean Delvare Hi Jean, I try to raise this every six months or so. Check the mailing list archive for "SNR" in the subject line. Yes, it's all screwed up and inconsistent across demods. I took a crack at fixing it a few months ago by proposing a standard (and even offering to fix up all the demods to be consistent), and those efforts were derailed by some individuals who wanted what I would consider a "perfect interface" at the cost of something that worked for 98% of the userbase (I'm not going to point any fingers). And what did we get as a result? Nothing. I could have had this problem solved six months ago for 98% of the community, and instead we are right where we have been since the beginning of the project. /me stops thinking about this and goes and gets some coffee.... 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 majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
