Hi,
I have an HVR-1900 with a problem that behaves like tuner frequency
drift when viewing or recording from DVB. I appreciate any help you can
offer to diagnose and resolve this problem. I am using the latest
mercurial download of v4l-dvb with a 2.6.28 kernel.
I first noticed this problem as a periodic degradation of the decoded
image, consistent with errors in the digital stream. Approximately every
10 minutes I would see picture disturbances that gradually ramp up in
severity until the video was no longer watchable, with severe audio
breakup. The video would then suddenly correct itself and play normally.
To investigate further I have spent some time recording signal levels
under various conditions with tzap. I have found that bit error rates
behave consistent with the picture errors I observe. The bit error rate
will idle around a fixed level (say 0x600), then begin to ramp up. As
bit error rate increases, I also see a reduction in both signal to noise
ratio and received signal level. As bit error rate exceeds approximately
0x4000 uncorrectable errors begin to increase. As bit error rate exceeds
approximately 0x5000 it will suddenly drop back to the initial quiescent
level with corresponding increases in signal to noise ratio and received
signal.
I say approximately every 10 minutes as this is typical, although I have
observed cycle times as low as every 90s, and as long as several hours.
I have observed the fastest cycle times after a cold start. This showed
an initial cycle of about 10 minutes, but had decreased to 90 seconds
after 2 hours. This leads me to believe that the root cause is something
in the tuner drifting with temperature. After the 2 hours I tried tuning
to another channel with a different frequency, then back to the original
channel. The problem persisted with 90 second period. I then removed the
pvrusb2 and tda10048 modules and inserted pvrusb2 again. After this the
no further problems were observed for the following 2 hours. Maybe the
HVR-1900 samples some temperature dependent parameter at boot, and with
the equipment at a stable temperature after the initial 2 hour soak, the
drift is much less evident.
I have not observed the problem using Windows. Does the windows driver
cause some sort of periodic reset to avoid the problem? I have not used
the hardware with Windows very much, so it is possible that I have just
not noticed it. I plan to repeat the cold start test using Windows soon.
In case the problem was resolved in the tda10048 firmware that windows
used, I spent some time tracking down the firmware in the Windows
driver. Looking in the Hauppauge 1.2a CD download I eventually found it
in Drivers/Driver73/Hcw73bda.sys. It was at a file offset of 471424 with
a length of 25098. Since it has a different length to the normal
dvb-fe-tda10048-1.0.fw, I had to adjust the tda10048 kernel module to
use it. Unfortunately, I have not noticed any difference using the newer
firmware.
Do you know of any good references to the architecture of the HVR-1900
and the chips used in it? Maybe looking though the device data sheets
would give me further clues.
How should I probe the devices with linux to discover the exact devices
used?
Gary
_______________________________________________
pvrusb2 mailing list
[email protected]
http://www.isely.net/cgi-bin/mailman/listinfo/pvrusb2
