toxibunny
Posts: 1382
Joined: Thu Aug 18, 2011 9:21 pm

Re: VGA and the FAQ.

Fri Sep 16, 2011 10:26 pm

It might be a reasonable idea to add a 'VGA?' Section to the FAQ, eiks niin?

Wasn't it James that said recently it'd add at least 15$ to the price but it was at the top of the 'add-ons after launch' list?

Not that every VGA thread needs locking, but you know...
note: I may or may not know what I'm talking about...

na1pir
Posts: 71
Joined: Fri Sep 02, 2011 4:43 pm
Contact: Website

Re: VGA and the FAQ.

Thu Nov 03, 2011 1:32 pm

Good idea because:
- "vga" is sub 4 char word so you cannot find it in forum only by "search forums" button,
- r-pi doesn't support VGA period, no more discussion about this.
- if you need it, you must convert HDMI/composite by means of some sort of converter box (25~55$ it might be good idea to sell it separably along with of cases, stickers,...).

garyamort
Posts: 15
Joined: Mon Oct 17, 2011 1:09 pm

Re: VGA and the FAQ.

Thu Nov 03, 2011 2:48 pm

Cheaper and more versatile to go with a USB to VGA adapter. http://www.newegg.com/Product/.....6812225007

NoSuchNick
Posts: 42
Joined: Tue Sep 20, 2011 1:38 pm

Re: VGA and the FAQ.

Thu Nov 03, 2011 3:32 pm

However that is usually ridiculously hardware intensive for any reasonable screen size. It also saturates the USB lines even more, which might become a problem if you try to transfer anything from the ethernet port onto an external harddrive at the same time.
Also make sure to buy one which has ARM compatible linux drivers.

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Montekuri
Posts: 449
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Re: VGA and the FAQ.

Thu Nov 03, 2011 3:32 pm

Abishur has said that a USB to VGA adapter is not a good idea in the topic about VGA:
Quote from abishur on October 20, 2011, 23:54
Yeah, we had discussed some USB to VGA adapters (possibly in another thread). The long story short is that even if it is possible I would *strongly* encourage users to find some kind of work around so they don't have to use it. A USB to VGA adapter is a software emulation of a video card. This means it takes a HUGE chunk of ram and processing power and on a system where these resources are at a premium it's just not a good idea!

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jojopi
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Joined: Tue Oct 11, 2011 8:38 pm

Re: VGA and the FAQ.

Thu Nov 03, 2011 4:58 pm

I have long wanted to try a USB VGA card as a kind of tech joke, but they are expensive and rare and it is very difficult to find out before buying one what chipset is in it and whether it stands any chance of working with X11. (Last time I checked, there was at least one chipset that was theoretically supported.)

I am not sure what is meant by "software emulation of a video card". If it supports only 1024x768 16bit 60Hz then that is already far more than USB2.0 bandwidth. So it must have a local framebuffer at minimum, and most likely some primitive blitting and/or painting functions. I would call that a real hardware graphics card, albeit one at the wrong end of a high-latency USB connection.

On the RasPi, even if you could find a compatible USB VGA adapter, there is the additional problem that you would lose the video decoding and 3D rendering functionality of the SoC GPU -- its two impressive features.

NoSuchNick
Posts: 42
Joined: Tue Sep 20, 2011 1:38 pm

Re: VGA and the FAQ.

Thu Nov 03, 2011 5:44 pm

Quote from jojopi on November 3, 2011, 16:58
If it supports only 1024x768 16bit 60Hz then that is already far more than USB2.0 bandwidth.
I guess they could get by with a RLE compression or maybe even something more advanced like huffman coding.
But even if it supports simple operations like line drawing and rectangle filling, just the virtual driver on the host side and the constant USB transfers are going to take up quite a bit of power.
I also always wanted to play around with one of these, but i haven't really found any task that would justify buying one.

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