[linux-dvb] Re: V4 API proposal

[Andreas Oberritter <andreas@oberritter.de>]

On Thu, 2003-03-13 at 23:16, Emard wrote:
> For the media source device, I propose 2 devices:
> One is raw TS dump device. There you can always
> get raw dump directly as it is received by the 
> vpeirq().

There is no vpeirq() in most drivers ;)

> Second device is not a single device, but a directory 
> of many demuxed devices, dynamically created/removed 
> upon current TS autodetection (scan) or when user forces 
> creation, by ioctl or preferrably from the shell just by
> touch /proc/<path>/<device>
> in special directory.

This "autodetection" is technically impossible. 
a) Not all hardware has the ability to provide a raw transport stream
b) If it had the capability, you would lose data between the time the
kernel creates the device and the user scans for directory entries.
Think of tables which are broadcasted at very low rates.
Besides that, I think you proposal is weird and I don't like it. :-)

> Insted of usb devices, we will have demuxed PIDs
> so /dev/dvb/adapter0/vpid245, vpid245, apid482 etc 
> should appear from the kernel demux automata.

See above. Additionaly this would require the kernel to
a) know what types of pids do exist (audio (how about ac3 - non-ac3),
video, teletext, different kind of sections)
b) identify them
As above, I think it is weird and I don't like it.

> Those devices will have raw mpeg dump or whatever
> appears as the PID. We can go thru usb high layer
> for them, so something like /proc/bus/usb/dvb0vpid245
> would be created that is equivalent to 
> /dev/dvb/adapter0/vpid245.

> Creation of such devices will trigger kernel hotplug 
> mechanism which in turn calls some shell script to 
> start mpeg decoding or playback

*sigh*

> Important thing in the above approach is that we have DVB
> tuning, reception demux and packet source stuff independent 
> from video4linux layer.

It is independant right now. The v4l layer is just an additional feature
for some dvb devices, not needed for most applications.

> Only consumer sink devices (record and playback devices) 
> will depend on video4linux layer.

Why? You don't need any v4l capabilities to record or playback to a
non-v4l device. Btw. v4l is missing essential things like proper
handling of video encoders (pal/ntsc/secam) or a/v-switches (s-video,
scart and stuff) you need for playback.

Remeber, pci dvb cards are more a spin-off product in the range of dvb
devices. Things that seem typical for them are rather unneeded and
unwanted for real dvb devices (a.k.a. set top boxes).

Andreas



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