Distorted video (and chopped audio) using xawtv etc. despite "v4l-conf had some trouble"

[TEN]

Binary package hint: xserver-xorg-video-v4l

Video from analog TV channels is shown distorted by black bars.
DVB video (digital TV) has block artefacts and chopped audio (the latter even occurs on DVB radio channels) whenever accessed by v4l (presumably upgraded to v4l2 in Ubuntu 8.04 "Hardy Heron").
The issue occurs in xawtv (output reproduced below) but can also be demonstrated in other applications such as the Ekiga VoIP client (formerly known as GnomeMeeting) when configured to use the same device as its video feed.

The audio distortion disappears as soon as the video display is closed with the source left running.

This as well as the fact that the same hardware performs just fine under a legacy Ubuntu 7.04 installed in parallel demonstrates that bad signal (i.e. weak TV reception leading to UNCorrectable errors) cannot possibly be the cause of these issues, although the symptoms may look similar at first glance.

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/230882 may be related.

mplayer and xine have no trouble playing back the same streams through other methods, such as streamed over http by a local VDR (a Linux "killer app" which is otherwise rendered unusable by this and a related issue with a buggy budget_av kernel module, cf. http://linuxtv.org/hg/v4l-dvb/rev/19964051c5f1, somehow conflicting with the serial port handling and hence driving system load through the roof, cf. http://vdr-portal.de/board/thread.php?threadid=77155 and http://vdr-portal.de/board/thread.php?threadid=77950 in German).

user@system:~$ xawtv &
[1] 6806
user@ubi:~$ This is xawtv-3.95.dfsg.1, running on Linux/i686 (2.6.24-19-generic)
xinerama 0: 1920x1200+0+0
X Error of failed request: XF86DGANoDirectVideoMode
  Major opcode of failed request: 137 (XFree86-DGA)
  Minor opcode of failed request: 1 (XF86DGAGetVideoLL)
  Serial number of failed request: 13
  Current serial number in output stream: 13
v4l-conf had some trouble, trying to continue anyway
v4l2: WARNING: framebuffer size mismatch
v4l2: me=1920x1200 v4l=0x0
Warning: Cannot convert string "-*-ledfixed-medium-r-*--39-*-*-*-c-*-*-*" to type FontStruct
ioctl: VIDIOC_REQBUFS(count=2;type=VIDEO_CAPTURE;memory=MMAP): Success
ioctl: VIDIOC_G_FREQUENCY(tuner=0;type=unknown;frequency=0): Invalid argument
ioctl: VIDIOC_S_STD(std=0x7 [PAL_B,PAL_B1,PAL_G]): Device or resource busy
ioctl: VIDIOC_S_FREQUENCY(tuner=0;type=ANALOG_TV;frequency=4294967295): Invalid argument
[lspci]
00:00.0 Host bridge [0600]: Intel Corporation 82865G/PE/P DRAM Controller/Host-Hub Interface [8086:2570] (rev 02)
     Subsystem: Fujitsu Siemens Computers Unknown device [1734:101b]
01:00.0 VGA compatible controller [0300]: nVidia Corporation NV18 [GeForce4 MX 440 AGP 8x] [10de:0181] (rev a2) (prog-if 00 [VGA controller])
     Subsystem: nVidia Corporation Unknown device [10de:0191]

[TEN (launchpad-20-ten)]

The first image appended to the original report shows distortion in analog TV shown by xawtv.

N.B. the bars may also be light and flickering in analog TV, as shown in the attachment to this comment.

[TEN (launchpad-20-ten)]

Below are the line artefacts appearing on DVB received on the card also used for playback through v4l(2).

N.B. signal reception issues would cause block artefacts instead.

[TEN (launchpad-20-ten)]

Finally, the block artifacts appearing despite fine reception when the video is transferred from the receiving card to the one providing the menu overlay and playback source for xawtv (et al.).

This is the only scenario where http://linuxtv.org/hg/v4l-dvb/log/19964051c5f1/linux/drivers/media/dvb/dvb-core/dvb_ca_en50221.c might contribute to the symptoms, also its bug is likely to have been present in the version used under Ubuntu 7.04 "Feisty Fawn" already, and didn't stop either xawtv or VDR from working fine there.

[Bryce Harrington (bryce)]

Hi launchpad-20-ten,

Thank you for taking the time to report this bug and helping to make Ubuntu better. You reported this bug a while ago and there hasn't been any activity in it recently. We were wondering is this still an issue for you? Can you try with the latest development release of Ubuntu? (ISOs are available from cdimage.ubuntu.com)

If it remains an issue, could you also attach a new /var/log/Xorg.0.log?
Thanks in advance.

The output of lspci -vvnn would also be worth having.

[Bryce Harrington (bryce)]

We're closing this bug since it is has been some time with no response from the original reporter. However, if the issue still exists please feel free to reopen with the requested information. Also, if you could, please test against the latest development version of Ubuntu, since this confirms the bug is one we may be able to pass upstream for help.

[TEN (launchpad-20-ten)]

Bryce,

the problem persists with Ubuntu 8.04 updated as of today.

Please find enclosed /var/log/Xorg.0.log ...

[TEN (launchpad-20-ten)]

... and the output of lspci -vvnn as requested.

[TEN (launchpad-20-ten)]

If this needs further discussion on a mailing list or IRC please specify...

[TEN (launchpad-20-ten)]

This shows VDR switched to a radio channel, hence the menu is the only "video" visible... with some flickering distortion even in this still image as displayed by xawtv...

[TEN (launchpad-20-ten)]

...which isn't in the actual image but generated only upon display by xawtv, as demonstrates this screenshot taken by pressing J in xawtv...

[TEN (launchpad-20-ten)]

...where part of the flickering portion remains on-screen after the menu is closed in VDR - so apparently V4L2/xawtv or the X drivers are trying to do some clever stuff here that goes wrong somehow.

Insights required on how to proceed further debugging this - thanks in advance for your replies!

[TEN (launchpad-20-ten)]

...where part of the flickering portion remains on-screen after the menu is closed in VDR - so apparently V4L2/xawtv or the X drivers are trying to do some clever stuff here that goes wrong somehow.

Insights required on how to proceed further debugging this - thanks in advance for your replies!

[bugbot (bugbot)]

This bug report was filed against an old version of Ubuntu.
Can you confirm whether this is still an issue in natty?

If you don't mind, it would be very helpful if you could update the bug
report in launchpad to 'Fix Released' if it is no longer an issue for
you, or if it is still occurring under natty, please tag the bug 'natty'
so it's easier for us to track.

[Launchpad Janitor (janitor)]

[Expired for xserver-xorg-video-v4l (Ubuntu) because there has been no activity for 60 days.]