Historically, these cards are used for two main purposes:
- Capture high-end, tape-based video formats like HDCAM, D1 and Digibeta through SDI/HD-SDI to uncompressed or near-uncompressed digital files.
- Previewing your work on a video monitor through a high bit depth, uncompressed SDI/HD-SDI or analog component video output.
For many users, the first purpose is slowly fading as most new formats in all segments (high and low-end) are file-based, ie stored in memory cards or hard drives and there's no need to capture them through a video input. Of course, many users still use them and will keep using them for some time to ingest tape-based formats.
The second purpose is still as useful as ever. But SDI or HD-SDI monitors are really, really expensive. Since some users use LCD TVs as a low-budger alternative, some models provide HDMI output as well (or instead of). For example, the Blackmagic Intensity series is an extremely affordable solution in this regard. AJA, Matrox and other vendors also have models with HDMI output, sometimes in addition to SDI and analog component.
AE has video preview capabilities built-in, so you can look at Comp updates and RAM previews on your video monitor/TV. Some vendors provide plug-ins so this works with their hardware. In other cases, it's not needed.
Getting into a more technical discussion, some users choose to use hardware or software technologies to make their computer displays behave in terms of color response like a digital TV or even other devices. A hardware solution would be, for example, the Decklink HD link. A software solution would be AE's built-in Color Management workflow. Calibrating your display with a calibration device is essential for this and they are quite affordable.
Using video hardware to feed SDI/HD-SDI, HDMI or analog component to a video screen is a more orthodox solution, if you want.
I think Decklink, AJA and Matrox are all very good. It's up to you evaluating price, external vs internal solutions, I/O options, etc.
Hey adolfo and thanks for replys
I have couple of more questions...
What about the advantages while editing?? Are there any? Does the videocards help prosessors when for expample rendering??
I have experieced some very long rendering times with cs4, especially now when I installed snow leopard. With SL I have also had a lot of crashes and freezes especially with premiere pro.... How much does graphic cards affect the rendering times? I have very poor graphic gard...
I have Sony xdcam ex1 camera. It provides two recording options. mpeg2 4:2:0 long-gop to a memory card and uncompressed 4:2:2 via hd-sdi. Can I capture the hd-sdi signal from the camera with videocards?? If I can is there any possibilities to use these videocards in macbook pro so I could take that with me to a location and capture with that???
Does the videocards help prosessors when for expample rendering?
No. At best, they accelerate decoding and playback of footage captured in their proprietary CoDecs, but that part is the least relevant for AE.
How much does graphic cards affect the rendering times?
Zero. For final rendering, AE defaults to software-only, which exclusively uses your main processor. Your graphics card will only be used, if you enforce OpenGL rendering by setting teh respective option.
Can I capture the hd-sdi signal from the camera with videocards?? If I can is there any possibilities to use these videocards in macbook pro so I could take that with me to a location and capture with that???
Yes, once you had such a card, capturing would be possible. For a mobile solution, you would consider an external box with a SDI to HDMI/ Firewire/eSATA converter and respective plug.
I have Sony xdcam ex1 camera. It provides two recording options. mpeg2 4:2:0 long-gop to a memory card and uncompressed 4:2:2 via hd-sdi. Can I capture the hd-sdi signal from the camera with videocards??
I have used such a setup to ingest greenscreen material from an EX1 camera, and the results were nothing short of amazing. One of the best keying sources I've seen, rilvaring the output from cameras costing many times more.
The Matrox MXO2 and AJA IO Express are examples of devices that could do this. But you need to talk to them regarding hardware and software support, because not all formats/codecs work on laptops, or may require additional software.
Also, be aware that your external card may need it's own power supply.