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Jonathan R. Haws <Jonathan.Haws <at> sdl.usu.edu> writes: |
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Hello, |
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> I am looking for a software API that I can use to develop a UI that will |
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> display an analog video stream on the screen with overlaid controls |
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> (buttons, indicators, etc.). |
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Maybe these are a good place to look at developing software for gentoo: |
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[1][2] |
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> The latency for the video |
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> display must be less than 1/4 second to meet the design requirements, so |
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> something that can be programmed in separate threads (a video thread and |
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> an overlay thread) may be the best option. |
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You'll need to find or develop a 'low latency' method to collect the video |
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(frames). I'm not so sure how experienced you are with video, so some of this |
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advice may not be relevant for you: |
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1. Look at the existing projects for frame grabbers and the device drivers |
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for the hardware portion of the related software: bttv/xawtv/camE has been |
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around for ever and the driver code has been fundamentally changed over time. |
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Here is a more current listing: [3] |
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Looking at some of the oldest driver code will show you have the 'bt848' chips |
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works. The bt848 chips have been replaced by new chips (878) and others. |
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Reading the data sheets on the chips will tell you quite a lot about |
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what is possible (This all assumes you are going to use a 'cots' |
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video capture hardware system that plugs into the pci slot of a (gentoo) |
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computer. If you are custom designing hardwareware (fpga, dsp, analog circuits) |
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then it may not be useful. |
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2. Find the relevant devise drivers for other chipsets used in video capture, |
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in the latest linux kernels for good places to look at what has already been |
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coded. This is a very dynamic area for device drivers (over the last few |
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years) so the driver code for a given video chipset and easily have changed |
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of the coarse of that time. |
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3. Look at ffmpeg and the developers therein, as you might be able to |
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learn quite a lot from previously (failed) projects and new efforts. |
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3. Keep you gui tools simple and lightweight. There are many graphical |
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toolkits you can use to create your graphics (UI). This is a huge, |
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separate effort. You may decide to use existing code for all of the low |
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level code and then just spin your own (UI) on top of a striped down |
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version of ffmpeg. My choice, QT4. |
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4. Read the sources to a lot of projects and talk to the folks at these |
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projects, before you start off 'half-baked'.....(caveat emptor)! |
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On gentoo here is a great place to begin your search: |
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cd //usr/portage/media-video |
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Other keywords |
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camstream Ogg OGM matroska |
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5. If you are looking into low latency video, for machine control |
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types of projects, then look into some 'image processing' areas |
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such as robotics for ideas in published 'white paper' and from |
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the standard journal publications. ACM, IEEE and the various |
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research area related to (computer) vision. |
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This is a very active, complex area you have chosen to work in. READ |
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(research) quite a lot and then narrow your focus on something that is |
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realistically achievable. Drop me some private email, if you like. |
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HTH, |
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James |
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[1] http://gentoo-wiki.com/HOWTO_Installing_3rd_Party_Ebuilds |
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[2] http://overlays.gentoo.org/ |
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[3] http://www.cs.cornell.edu/~reynolds/quickcam/ |
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-- |
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