On Tue, Dec 1, 2009 at 12:41 PM, Jeff Campbell <jac1dlists@gmail.com> wrote:
> Thanks for confirming things Andy, Devin.
>
> I am getting 21.5 to 22 on SNR, which seems quite low. This is for OTA
> signals. I'm used to 25++ on a cable network. I am quite a distance from
> the transmitting tower, and at a low elevation so perhaps it is to be
> expected. I'd be curious to hear what others are getting and their relative
> distance from the towers if they know it. I'm about 35 miles away.
Bear in mind that the expected SNR for ATSC is different than for
ClearQAM. For ATSC, you generally want an SNR no lower than 25. For
ClearQAM you generally want an SNR no lower than 30. These numbers
should not be any sort of "official standard" - just my general
experience. For the OTA case, I am a pretty crappy use case though,
since I am literally in the shadow of the Empire State building.
> It seems to be consistent across all three stations, which are all coming
> off the same tower as far as I am aware.
Should be easy enough to check - just look at your channels.conf file
and see if they are all coming from the same frequency.
> Generally the video performance is very good but I get occasional periods of
> lost packets and slight pixelation in small areas, which is consistent with
> being near the lower end of signal strength and losing a few packets.
Which application are you using? I have noticed that the different
MPEG2 implementations vary wildly in terms of how well they respond to
even the slightest of errors.
> At the moment I am using dvbstream to stream the output but I'm finding it
> dies with a buffer overflow error after a random period of time. I suspect
> this may be related to the signal strength and mangled packets, but I
> haven't looked in to it in any detail yet. Is dvbstream normally stable for
> long term streaming?
I don't have much experience with dvbstream. Typically I use
something like mplayer or Kaffeine to watch the stream, and then run
femon in a separate window.
Devin
--
Devin J. Heitmueller - Kernel Labs
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