Where to get help
- IRC with us at #tvtime on irc.freenode.net.
- Post bugs on our
Sourceforge bug tracker.
- Subscribe to the
tvtime development mailing list.
Frequently asked questions
- How do I disable deinterlacing?
- Does tvtime support recording?
- Why is the tvtime window appear
pink in screenshots?
- I see purple lines in the video from my
DVD player. How do I avoid Macrovision copy-protection?
- Interference problems with soundcards
- Optimal settings for tvtime on TV
- Does tvtime support FreeBSD or NetBSD?
- How do I force the screenshots to be a specific filename?
- Does tvtime support any architectures besides x86?
- Where is the "canada-cable" frequency table?
- How can I map audio to my digital
- My capture card does not have an audio
output jack, what do I do?
Many users seem confused about what the deinterlacing plugins do
and what it means to disable them. The signal output from almost any
video source, be it a Gamecube or cable TV, is an interlaced video
signal. Implicitly when you display this on a computer screen, you are
deinterlacing: you're taking interlaced content and displaying it on a
The simplest way to do this, and the default in some TV applications,
is to buffer every two consecutive fields together and show them
as a single frame. You can do this in tvtime by setting it to one of
our Progressive modes. That's about as close to "not deinterlacing"
as you can get, but it's still deinterlacing.
Ideally, tvtime would be able to detect progressive content sent
over an interlaced channel, such as the output from some video games
or DV cameras in progressive mode. This feature is something we
would like to have in a future release.
tvtime does not support recording or playback of recorded
streams, and it is unclear to us if this is in the scope of what
tvtime should try to accomplish. Many users ask for this feature,
but they have very different goals. Some users want a quick way to
record small, low-quality clips from television. Some want a high
quality recorder for recording shows. Others want to have a full PVR
system integrated into tvtime.
Currently, we would rather focus on making tvtime the best high
quality live TV viewer for Linux, with a clean and consistent user
experience. We recommend using mencoder for recording
from television, and systems like MythTV or freevo for
a PVR system. If you are interested in coding some sort of
support for recording in tvtime, please contact us so we can discuss
how it might best be integrated into tvtime.
tvtime outputs video into a video overlay surface, an area
of video memory outside of the framebuffer, using the XVIDEO
X extension. Applications which take screenshots such as
ksnapshot, gimp or xwd only see the
colourkeyed window, and not output of tvtime.
We believe it is a design flaw or driver limitation of the X
server or video card hardware that neither can provide the image
to screenshot applications. For this reason, the only known method
of taking screenshots of tvtime along with the desktop is to use the
screenshot feature inside tvtime, and cut-and-paste the
output into a full desktop screen capture.
If you are seeing purple lines or having problems with video signal
quality from an external DVD player, VCR, or Laserdisc player, try
disabling Macrovision in your bttv driver (if you have a bttv card).
for information on how to do that.
If you are experiencing a generally fuzzy picture, try moving your
tv card one or two slots away from your soundcard (inside your pc).
Interference from the soundcard can mess up some channels.
Some people are interested in using tvtime even when their output
itself a television. Usually this is in the context of setting up a
home theatre PC system. Ideally for television output, no
deinterlacing is required; the interlaced signal is sent to the output
such that every top field in the input is mapped to a top field in the
Unfortunately, there is no standard TV output API under Linux. The
VESA framebuffer setup for TV output cannot tell us which field is
currently being displayed. Similarily, some TV output setups under
Linux have it as a second head in X, but again, with no field
information. We cannot know how to supply it with interlaced content
to ensure that fields are shown in the right order.
That said, I have been told that when using the NVIDIA TV output
drivers, supplying them with top-field-first frames will cause
it to display the fields correctly. To experiment, try tvtime
using the Progressive: Top Field First deinterlacer.
Please let me know if this
gives good results.
Currently, tvtime will not work on BSD-based systems, but the
code to get it to work should not be too difficult.
There is a driver for bt848 and bt878-based cards under BSD called
bsdbt848. The API for this driver is different from Linux's
video4linux that tvtime was written for, so the first job would be to
do the input code in tvtime to handle this driver. See
mplayer for one example of some code
that uses this driver.
The only other Linux-specific feature that we use would be the
/dev/rtc code to do high performance timing (I assume there is a BSD
equivalent of this).
If you make any progress on any of these, please let us know.
tvtime's screenshots can be given a filename when requested
using tvtime-command. Simply do:
tvtime-command SCREENSHOT "current.png"
And the screenshot will output as current.png. This is
useful for scripts which upload the latest image from the TV to a
webpage, for example.
Some work was done by Helge Kreutzmann to try tvtime on
alpha Linux. We determined that disabling the wine loader was
enough to get tvtime to compile and run. tvtime 0.9.11 should
compile at least on this architecture.
Besides that, most other architectures are simply untested.
If anyone is seriously interested in another architecture, has
some coding ability, and has sufficient hardware resources to try
tvtime on another architecture, please email me at
As a miminum, your system should have a video card that can
handle high bandwidth uploads (in our default configuration we
upload 40 megabytes per second) and supports hardware video
overlays, preferably using the XVIDEO extension. As well, we require
a video4linux or video4linux2-compatible driver and about the CPU
power of a reasonable P3.
If you needed to use the "canada-cable" frequency table in
another TV application, then your capture card's tuner has been
misdetected as a PAL tuner when it is actually an NTSC tuner. Please
see this support question on our
hardware support page for information on how to fix this
Many bt878-based cards also support digital capture of the
audio. This can be accessed using the btaudio kernel
module, which registers an OSS sound device that supports 32 KHz
audio capture. On a capable card, loading the module gives
something like this in your system logs:
btaudio: driver version 0.7 loaded [digital+analog]
btaudio: Bt878 (rev 2) at 01:0b.1, irq: 6,
latency: 64, mmio: 0xf16ff000
btaudio: using card config "default"
btaudio: registered device dsp2 [digital]
btaudio: registered device dsp3 [analog]
btaudio: registered device mixer1
On my system /dev/dsp2 can now be used to read
digital audio from the card at 32 KHz. This can be then sent
out to an arbitrary soundcard using a program such
sox -r 32000 -w -t ossdsp /dev/dsp2 -t ossdsp /dev/dsp
This command reads the input at 32 KHz from
/dev/dsp2 and writes it out to my soundcard
at /dev/dsp. Having this run while using tvtime
will enable you to perform arbitrary maps of the audio, such
as playing it out the digital output of your soundcard.
If your capture card does not has a pass-through audio
jack, you can use the technique
described above to map the audio from the internal
digital capture out to your soundcard.