Tuesday, June 23, 2009

TVProgramGuide - my application for tv tuners

This is about an application that I've recently developed, that can show real-time TV programme guide lines on the fly over a TV tuner video.

It is really interesting to see how subtle things can make a big difference in the way we carry out every day life. This idea struck my mind few weeks back, when I landed at entertainment.oneindia.in accidentally while trying to find out what movies are played for the day. The idea was to integrate this info about TV programmes into the existing TV tuner application, so I can fetch them whenever I need them. When I was first thinking about this idea, I didn't really expect it to be soo useful -- today I just can't watch TV without the aid of this app.

The idea sounds interesting but it is as vague as a patent. I spent the first week thinking about the feasibilty of this application, and about how to integrate this app into the TV system. I was pretty clear that this app is going to be of no-use if I cannot provide a means to use this application wirelessly (yes, using the TV remote). If I have to come to the comp, and use the mouse to find out 'what's coming up next?', I would rather visit the website in my browser and know about it. It is as simple as having a bookmark in my browser.

But I wasn't sure if I can hook into the TV remote, and get its signals. Even if I can, I should also ensure that my hooking does not affect the normal functioning of the TV tuner application, that is already using the TV remote and reacting to the signals. As specified in my earlier post on my TV tuner, the tuner's hardware (Trident) and the TV tuner application (Honestech) seem to be from different vendors -- this gave me the hope that there should be an interface available somewhere (although unpublished) using which the existing TV tuner app is receiving the TV remote key presses. I will definitely be writing a separate post on the technical details of how and what disassembling I had to do; but for now, it is that I've managed to discover the undocumented APIs that are used internally, and the appropriate DLLs and managed to hook into them seamlessly so the TV tuner application has no idea that I'm hooked in.

This hooking was done in C/C++. The remaining task was to download the TV programmes from their website (note: oneindia does not have the list for all channels. So I had to do a generic design to support any website; with abstract classes and interfaces, this isn't a problem anyway). For any non-system programming I prefer python (if not UI related) and C# if it has an associated UI. I admire the power of the modules/class libraries that these platforms provide; awesome! .Net comes handy with Http classes (System.Net.HttpWebRequest) to handle the HTTP requests/responses for downloading the programmes. And I used RegEx (System.Text.RegularExpressions.RegEx) to parse the HTML output and extract the program schedule. With a number of choices for sharing info (remote key press) between the C/C++ hook and the C# interface, I chose the simplest one: The windows registry. I intend to post a developer post on this later, but that's the overall technology behind this app.

Important features:

1. Automatically shows the 'now playing' programme on every channel change. The 'now playing' item is picked based on the current channel no. and the current time. This window shows up for 10 seconds and auto-hides. Very useful when we glance through the channels.
2. Channel change is detected by monitoring the remote key presses including numbers, up, down, recall etc., Interesting part was that channels can be changed by a sequence of key presses eg., key 1 followed by key 2 followed by key 3 in a short interval, is not 3 different channel changes, but a single change to channel no. 123. It had to be handled differently.
3. A special mode can be entered by a special key combination (that does nothing to the tuner app) in the TV remote. In this mode, the app overlays the 'coming up next 5' programmes list over the video. This info does not auto-hide. It can be closed by the Mute key on TV remote.
4. Seamless integration, so TV tuner works just well as before.

Here is the video showing my application in action as I watch TV on my comp:

Overall, I'm very happy with this app; one of my applications that I use the most. I'm hopeful to publish this app soon, after I make some generalizations (currently channel associations are hard-coded and not all channels are supported).


  1. Nice app. Does it support the external TV tuner cards(though it is obsolete nowadays)?

  2. I don't understand what you mean.

    This app is for TV Tuners that run on a computer (the card being internal PCI card or the external USB device). In fact, my tuner is an USB based external tuner.

    If you are talking about the totally external ones (which do not need a computer but directly connect to the monitor), the question is invalid.

  3. Thanks. Sorry for asking you such a blunt question that you explained about the "undocumented API's" and the dll's for TV tuner card which can be processed only with a help of the system, which means the TV tuner card should be an internal one.

  4. Not really. USB based TV tuner cards (the one I've) are totally external, but are driven by software (the device can be plugged in or out anytime when the system is running, just like any USB device).

  5. I meant the "internal one" in the sense that regardless of whether a device can be seen by the eyes, (i.e it is inside the cabinet or outside the cabinet), It has an interface with the CPU via motherboard.

    Sorry if you had misinterpreted or that I made an ambigous comment.

    Thank you anyway..