[linux-dvb] How to access /dev/videoK from /dev/dvb/adapterN?

Klaus Schmidinger Klaus.Schmidinger at cadsoft.de
Sat Jun 17 10:59:59 CEST 2006

Manu Abraham wrote:
> Ralph Metzler wrote:
>> Klaus Schmidinger writes:
>>  > An application that uses the LinuxDVB driver can access the
>>  > DVB devices via /dev/dvb/adapterN/* (N = 0, 1, ...). However,
>>  > when it wants to, for instance, capture the current image on
>>  > a device (like VDR with its GRAB command), it needs to access
>>  > /dev/videoK, where 'K' is a number that is not directly related
>>  > to the 'N' mentioned above for the DVB device.
>>  >  > So VDR has to do some guessing on which /dev/videoK device might
>>  > belong to the /dev/dvb/adapterN device. This is getting particularly
>>  > problematic if there are also other /dev/video devices that have
>>  > nothing to do with any DVB devices.
>>  >  > Is there a defined way in which an application can query a DVB
>>  > device for its related /dev/video device?
>> Currently not.
>> Since upcoming cards with decoder and V4L interface for those will
>> need it too, should we add a call for this? In the DVB video device?
>> We might also need something like this for audio.
> Like what we discussed earlier, what about making the nodes children to 
> the adapter device, this will shoot at least 2 or 3 birds in one shot. 
> ie a /dev/dvb/adapterX device, all are just child nodes of the adapter 
> device.
> This would solve
> (1) solve the issue with the demux for multistandard devices
> (2) This current situation
> (3) Calls that might belong to more than one device/belonging to the 
> card etc

I wouldn't mind _where_ the video device is that I need to use
for grabbing the image, so that would be fine with me.

However, the name /dev/dvb/adapterN/videoM is already taken - or
could that same node be used for image grabbing?


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