Where to get help

1. IRC with us at #livid on irc.freenode.net.
2. Post bugs on our Sourceforge bug tracker.
3. Subscribe to the tvtime development mailing list.

Frequently asked questions

1. How do I disable deinterlacing?
2. Does tvtime support recording?
3. Why is the tvtime window appear pink in screenshots?
4. I see purple lines in the video from my DVD player. How do I avoid Macrovision copy-protection?
5. Interference problems with soundcards
6. Optimal settings for tvtime on TV output
7. Does tvtime support FreeBSD or NetBSD?
8. How do I force the screenshots to be a specific filename?
9. Does tvtime support any architectures besides x86?
10. Where is the "canada-cable" frequency table?
11. How can I map audio to my digital output?
12. My capture card does not have an audio output jack, what do I do?

1. How do I disable deinterlacing?

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 non-interlaced display.

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.

2. Does tvtime support recording?

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.

3. Why does tvtime appear pink in screenshots?

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 on the X 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.

4. I see purple lines in the video from my DVD player. How do I avoid Macrovision copy-protection?

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). See http://www.colby.edu/personal/k/kjseptor/bttv.html for information on how to do that.

5. Interference problems with soundcards

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.

6. Optimal settings for tvtime on TV output

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 output.

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.

There are two possible solutions. I have been told that with the NVIDIA TV output drivers, when using XVIDEO, if you supply them with top-field-first frames, they will display the fields correctly. To experiment, try tvtime using the Progressive: Top Field First deinterlacer. This may give good results. The second option would be using a card with a TV output driver that gives field information. An example is the Matrox G400/G450/G550 driver in DirectFB. We have an output mode in tvtime specifically for this driver, but it is experimental and currently not being further developed.

7. Does tvtime support FreeBSD or NetBSD?

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 features that we use would be the /dev/rtc code to do high performance timing (I assume there is a BSD equivalent of this), and potentially the wine loader for the DScaler DLLs may need updating.

If you make any progress on any of these, please let us know. Thanks.

8. How do I force the screenshots to be a specific filename?

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.

9. Does tvtime support any architectures besides x86??

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 vektor@dumbterm.net.

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.

10. Where is the "canada-cable" frequency table?

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 problem.

11. How can I map audio to my digital output?

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 as sox.

    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.

12. My capture card does not have an audio output jack, what do I do?

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.