> Em Thu, 22 Oct 2009 21:13:30 +0200 > Jean Delvare <kh...@linux-fr.org> escreveu: > >> 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. > > We all want to know about that ;) > > Seriously, the lack of a description of the meaning of the ranges for > those > read values were already widely discussed at LMML and at the legacy dvb > ML. > We should return this discussion again and decide what would be the better > way to describe those values. > > My suggestion is that someone summarize the proposals we had and give some > time > for people vote. After that, we just commit the most voted one, and commit > the > patches for it. A pending question that should also be discussed is what > we will > do with those dvb devices where we simply don't know what scale it uses. > There > are several of them. > > Btw, the new official documentation is the media infrastructure docbook > that > can be found at the Kernel and at: > http://linuxtv.org/downloads/v4l-dvb-apis > > This covers both DVB and V4L API's.
We did discuss this briefly during the v4l-dvb mini-summit and I know Mike Krufky knew what to do about this, but for the life of me I can't remember what it was. I should have made a note of it... Mike, can you refresh my memory? Thanks, Hans -- Hans Verkuil - video4linux developer - sponsored by TANDBERG Telecom -- 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