On Mon, Jul 9, 2012 at 11:19 PM, Tim Stowell <stowellt@xxxxxxxxx> wrote: > Hello, > > I'm trying to create a bitmap image such that when output via a > composite port it will translate into captions, very similar to this: > http://al.robotfuzz.com/generating-teletext-in-software/ except NTSC. > I have some ideas but wanted to check if anyone had tried something > similar as Google didn't turn up much, thanks! I don't know if this is related to your previous thread about VBI capture on em28xx, but if so I can tell you that you can probably pretty easily "pass through" the VBI data as a graphical waveform if that is your goal. The only difference between the data provided via raw VBI capture and the standard image data is that the chroma is stripped out (every other byte in a YUYV sequence). If your goal is to generate the waveform from scratch, I haven't seen any software to do that but it would be pretty trivial to write (probably a couple hundred lines of code). You just need to read the EIA-608 spec and understand how the byte pairs are represented in the waveform. You should also look more closely at the zvbi source code - it has the ability to create a "dummy source" which if I recall actually can work with osc (meaning it can generate the waveform internally). You would have to hack up the code to connect the parts and extract the actual image data. It's probably also worth mentioning that much of this is dependent on the output device you are using. Many devices don't actually let you put data into the VBI area just by including it in the image data. You typically have to use special APIs that are specific to the platform. Devin -- Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
