[linux-dvb] V4L vs DVB

Mark Howells Mark.Howells at softoption.com
Wed Sep 20 13:03:29 CEST 2006


Hi,
 
I'm not sure if this is the right place for this so I apologise in advance if it's not. I'm just about to start working with a V4L driver and it occurs to me that my understanding of the differences between a DVB driver and a v4l driver are hazy at best. Therefore I'd appreciate a steer to a decent overview/summary document (there doesn't appear to be such a thing on linuxtv.org) comparing the two mechanisms.
 
>From what I've gleaned the DVB interface provides access to a raw MPEG stream via PIDs etc via entries /dev/dvb/adapterX/*, whereas the V4L interface provides access via /dev/video to an already decoded video stream. Doesn't this mean that the quality of the resultant image is dependant upon the quality of the card manufacturer components (i.e. cheap units are likely to give poor perfomance) whereas with DVB devices a cheap device should give identical results to a higher quality unit (assuming a decent tuner lock) as in both cases we're just getting a bitstream? Also, for recording systems (I intend to use VDR) we'll be recording in MPEG or whatever so isn't there an additional decode/encode process? I.e.
    DVB(MPEG)->VIDEO->MPEG->file
compared with 
    DVB(MPEG)->file
and if so, wouldn't simpler DVB devices be better for PVR purposes?
 
Thanks
 
Mark

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