[mythtv-users] DVB recordings quality problem

Kari Salmela kari.salmela at lanwan.fi
Sat May 27 19:39:00 UTC 2006


Hello

Lately with new builds (<1 month) I have been experiencing problems with 
recording or watching live tv. It seems like signal would be bad, but I 
have checked and double checked the cables and everything should be okay 
on that side. With set top box the signal is flawless. The system is 
only 1-5% CPU load when recording. I have too little memory for the box 
(512MB) currently but I am not sure whether this is the problem since it 
used to work without problems earlier. I will get more RAM hopefully 
soon, and maybe the problem disappears. Meanwhile, is anyone else 
getting this and/or found out a solution? Any ideas how to debug this? 
Sometimes (2-3 out of ten) recordings are ok, but there seems to be no 
common factor when everything works.

The errors in mythbackend.log are like this when recording:

2006-05-27 22:07:44.439 DVBRec(0): PID 0x28c discontinuity detected
2006-05-27 22:07:44.440 DVBRec(0): PID 0x240 discontinuity detected
2006-05-27 22:07:44.441 DVBRec(0): PID 0x28a discontinuity detected
2006-05-27 22:07:44.442 DVBRec(0): PID 0x28d discontinuity detected
2006-05-27 22:07:44.439 DVBRec(1): PID 0x161 discontinuity detected
2006-05-27 22:07:44.444 DVBRec(1): PID 0x261 discontinuity detected
2006-05-27 22:07:44.445 DVBRec(1): PID 0x361 discontinuity detected
2006-05-27 22:07:44.443 DVBRec(0): PID 0x28e discontinuity detected
2006-05-27 22:07:44.515 DVBRec(1): PID 0x102 discontinuity detected
2006-05-27 22:07:44.534 DVBRec(1): PID 0x103 discontinuity detected
2006-05-27 22:07:44.536 DVBRec(1): PID 0x0 discontinuity detected
2006-05-27 22:07:44.536 DVBRec(1): PID 0x6b discontinuity detected
2006-05-27 22:07:44.663 Writing PAT & PMT @213235804 + 1484448
2006-05-27 22:07:44.711 DVBRec(0): Packet dropped due to uncorrectable 
error.
2006-05-27 22:07:44.713 DVBRec(0): Packet dropped due to uncorrectable 
error.
2006-05-27 22:07:44.714 DVBRec(0): PID 0x200 discontinuity detected
2006-05-27 22:07:44.714 DVBRec(0): PID 0x28e discontinuity detected
2006-05-27 22:07:44.825 DVBRec(1): PID 0x6e discontinuity detected
2006-05-27 22:07:45.001 DVBRec(0): Packet dropped due to uncorrectable 
error.
2006-05-27 22:07:45.002 DVBRec(0): PID 0x200 discontinuity detected
2006-05-27 22:07:45.003 DVBRec(0): PID 0x28e discontinuity detected
2006-05-27 22:07:45.047 DVBRec(0): PID 0x28c discontinuity detected

and when playing the recording, there are dropouts and clicks in the sound.

When looking at my dmesg, I see that one dvb card is sharing interrupt 
with ethernet adapter (irq11) and irq5 used by other card is also used 
by usb, but no usb devices are connected to system. Do you think this 
could be the problem? I have moved cards to improve air circulation in 
the box, but made other changes at that time as well.

I also tried hdparm according to suggestions in the mailing list, but it 
don't seem to help.

mythtv:/var/log/mythtv# hdparm /dev/hda

/dev/hda:
 multcount    = 16 (on)
 IO_support   =  3 (32-bit w/sync)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 24321/255/63, sectors = 390721968, start = 0

Setup:
M/B Asus A7V266-EX, 512MB RAM, Athlon XP 2400+, NVidia FX5200, Seagate 
S-ATA 160GB
2 x Technotrend DVB-C budget cards
Linux 2.6.15.6 on Debian testing

mythtv:/var/log/mythtv# mythbackend --version
Library API version: 0.19.20060522-1
Source code version: 10047
Options compiled in:
 linux release using_xvmcw using_v4l using_oss using_alsa using_arts 
using_jack using_ivtv using_firewire using_dbox2 using_hdhr using_ip_rec 
using_lirc using_joystick_menu using_dvb using_x11 using_xv using_xrandr 
using_xvmc using_xvmc_vld using_frontend using_backend

Best regards

Kari



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