I wanted to do some light measurements (illuminance, to be exact), but didn’t want to spend hundreds of euro’s on a light meter. I realized that I actually have a quite good light meter in my pocket: my smartphone’s camera. It doesn’t measure illuminance, but luminance, but that can be worked around.
Posts tagged ‘iPhone’
To get secure access to internal networks, one usually employs one of the many variants of a VPN. When connecting from a normal computer, you can install basically whatever variant you wish. When using devices such as smartphones however, the number of supported VPN technologies is usually limited. Especially on non-open platforms such as the iDevices by Apple, you can not add VPN software yourself, contrary to the Android platform.
In this post, I’ll explain how to set up an IPsec (without L2TP) tunnel endpoint on an Ubuntu server, capable of handling an iPhone/iPad/iPod/iWhatever. The users will be authenticated against an LDAP directory.
One very nice feature the iPhone lacks is the ability to request a delivery report on text messages. I usually abuse these by sending a text message to family/friends while they’re on a plane. As soon as they land and switch on their phone, I get a delivery report. Which essentially tells me “for free” that the person has landed. (With Belgian carriers, receiving text messages is always free, even abroad, because you can’t refuse them).
The internet is filled with guides and howto’s for getting video on you iPhone. The specs specify the iPhone to support h.264, baseline profile, level 3.0. Translated this means:
- No B-frames
- No CABAC
- No weighted predictions
- No 8×8 DCT
- Max resolution around 640×640 (technically 1620 MacroBlocks, 16×16 each)
- Max 25fps at that resolution (technically 40500 MacroBlocks per second)
- Max 10Mbps
The iPhone imposes some extra limitations:
- Max 640×480, 30fps
- Max 2.5Mbps
Most guides on the internet additionally force the number of reference frames down to 1 (ffmpeg‘s -refs parameter), although I could no find any specsheet imposing this limit. So I decided to test this.