[gull] Mon adaptateur roline hdmi to VGA ne fonctionne pas sur ubuntu

[Daniel Cordey]

>>>>>> Malheureusement, mon moniteur vga brancher à l'aide de cet
>>>>>> adaptateur m'affiche le message "no vidéo output" ou devient tout
>>>>>> simplement noir.

En effet, les commentaires au sujet de l'alimentation du dongle me 
semblent pertinents. Le signal VGA étant analogique, le "convertisseur" 
produisant un signal digital, il doit bien y avoir quelque chose qui 
alimente le chip qui fait la conversion à l'intérieur du dongle...

Donc, soit celui-ci est alimenté par le HDMI, soit par le VGA, soit de 
manière externe avec un mini-usb. S'il n'y a pas de mini-usb, 
l'alimentation doit-être fournie par l'un des deux connecteurs... 
Normalement, le "device" actif du HDMI devrait fournir 55 mA sous 5V, 
mais...


An HDMI device that has active electronics should have a provision for 
external power in order to be compliant (e.g. a receptacle to allow the 
use of a standard power adapter, sometimes called a power “brick”). Here 
we are drawing a distinction between “active” devices that actually have 
some powered electronics, and “passive” devices, such as some switches 
(more on those later).

Some active devices, such as actively powered HDMI cables or in-line 
signal extender boxes, will by default attempt to power their 
electronics by taking power from the 5V line (+5V power) available on 
the HDMI connector. The HDMI specification requires all source devices 
to provide at least 55mA (milliamps) on the 5V line for the purpose of 
reading the EDID of a display. While 55mA is not enough current to 
operate most HDMI accessory devices (which typically require about 100 
to 150mA), most source devices on the market today provide significantly 
more current on the 5V line than the HDMI specification requires. As a 
result, the vast majority of accessory devices can operate when 
interfaced with a source device that provides more than the required 
current (i.e. over 100-150mA) on the 5V line. However, manufacturers 
should provide a provision for their powered HDMI accessory devices to 
obtain external power, and consumers are encouraged to look for this 
external power provision when purchasing such products.

Looking to the future, not all HDMI devices may provide this much power 
over the 5V line. For example, as HDMI expands into more and more 
portable applications (cameras, camcorders, laptops, etc.), power 
consumption is often much more of an issue, and such devices may not 
power the 5V line with the > 100mA required by such “active” devices. 
Again, consumers should consider ensuring that their active HDMI 
accessory device purchases have a provision for external power for this 
reason.

Any device which performs processing, amplification, or switching of the 
HDMI signal should use actively powered electronics to be compliant and 
perform reliably. As mentioned in the above question, the vast majority 
of devices can utilize power that is supplied on the 5V line (+5V power) 
of the HDMI connector to function properly, although we recommend that 
such devices give the users an optional provision to use an external 
power adapter. Completely passive, non-powered devices may work in some 
short-cable length applications, but use them at your own risk, as they 
may not operate reliably. Even if a passive device works in one 
configuration, a change in equipment or cabling may introduce failures 
in subsequent configurations.

J'aurais donc tendance à dire que le dongle n'est pas alimenté, ou qu'il 
a besoin de trop de courant que ce que peut fournir le HDMI... Ce qu'il 
fait qu'il ne sort aucun signal VGA du dongle...

dc