Richard Brown wrote:
Yes. All (or at least nearly all) tuners in production today will fine tune to try to find the "sweet spot" for the signal once given a frequency. Unfortunately, the initial frequency must be close enough to the proper frequency to allow fine-tuning to succeed.Does anyone know the answer to the question I posted earlier in this thread about whether auto fine tuning exits for the LG tuner (or other tuners) used on the PVR-[2,3]50 boards?
Specifically:
(1) does the tuner hardware perform fine tuning natively?
(2) does the ivtv driver implement fine tuning? or it is possible toDone in hardware. Not directly controllable by the driver. However, if the driver does not properly pass commands (i.e. it uses short-cut tuning methods), it can put the tuner in a state where fine-tuning is impossible. This is especially likely when switching between frequency ranges (i.e. VHF, UHF-LO, and UHF-HI). The Linux tuner driver issues the appropariate commands to prevent this. Also, tuners typically provide a "fast-tuning" method which more quickly picks up the new channel, but is less accurate at fine tuning. The Linux tuner driver uses slow-tuning to ensure the best quality video. Note, also, that the speed difference between the slow-tuning and fast-tuning method is a negligible part of channel changing with the PVR-x50 (because of stopping/starting the encoder and waiting to have enough video to begin encoding).
implement fine tuning control?
It seems that some control over fine tuning the video carrier may helpThe unfortunate truth is that the weaker the signal the less likely fine-tuning will work. If the signal is too weak to be tuned, the signal-to-noise ratio is generally great enough that the "sweet spot" seems to change over time. This can mean that each time you tune the channel, the quality of the picture changes--sometimes showing a better picture than other times--but seeminly without pattern.
bring in weaker signals.
Most applications that use the PVR-x50 provide some sort of "fine-tuning" capability with which you adjust the initial frequency requested of the tuner relative to the frequency defined in the frequency table. MythTV allows you to do this using MythWeb's settings page. You can also use ptune to tune channels manually if not using a higher-level application. However, generally if the signal is weak, you'll never find a setting that reliably gives a good picture every time you tune the channel because of the change over time described above.
Therefore, the best fix, IMHO, is to amplify the signal--as close to the "source" (antenna or cable's entry into the house) and especially before splitting it--and ensuring a good signal-to-noise ratio.
Mike
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