Re: DVB core enhancements - comments please?

[Antti Palosaari <crope@iki.fi>]

On 06/29/2012 03:02 PM, Mauro Carvalho Chehab wrote:
> Em 29-06-2012 02:03, Antti Palosaari escreveu:
>> On 06/29/2012 07:32 AM, Mauro Carvalho Chehab wrote:
>>> Em 27-06-2012 21:33, Antti Palosaari escreveu:
>>>> SDR - Softaware Defined Radio support DVB API
>>>> --------------------------------------------------
>>>> * http://comments.gmane.org/gmane.linux.drivers.video-input-infrastructure/44461
>>>> * there is existing devices that are SDR (RTL2832U "rtl-sdr")
>>>> * SDR is quite near what is digital TV streaming
>>>> * study what is needed
>>>> * new delivery system for frontend API called SDR?
>>>> * some core changes needed, like status (is locked etc)
>>>> * how about demuxer?
>>>> * stream conversion, inside Kernel?
>>>> * what are new parameters needed for DVB API?
>>>
>>> Let's not mix APIs: the radio control should use the V4L2 API, as this is not
>>> DVB. The V4L2 API has already everything needed for radio. The only missing
>>> part ther is the audio stream. However, there are a few drivers that provide
>>> audio via the radio device node, using read()/poll() syscalls, like pvrusb.
>>> On this specific driver, audio comes through a MPEG stream. As SDR provides
>>> audio on a different format, it could make sense to use VIDIOC_S_STD/VIDIOC_G_STD
>>> to set/retrieve the type of audio stream, for SDR, but maybe it better to just
>>> add capabilities flag at VIDIOC_QUERYCTL or VIDIOC_G_TUNER to indicate that
>>> the audio will come though the radio node and if the format is MPEG or SDR.
>>
>> SDR is not a radio in mean of V4L2 analog audio radios.
>
> Why not? There's nothing at V4L2 API that limits it to analog, otherwise it couldn't
> be used by digital cameras.
>
>> SDR can receive all kind of signals, analog audio, analog television, digital radio,
>> digital television, cellular phones, etc. You can even receive DVB-T, but hardware I
>> have is not capable to receive such wide stream.
>
> The V4L2 API has everything to control receivers. What it doesn't have (and it doesn't make
> sense to have, as such thing would just duplicate existing features at DVB API)
> are the per delivery-system specific demodulator properties and PID filtering.
>
>> That chip supports natively DVB-T TS but change be switched to SDR mode. Is it even possible
>> to switch from DVB API (DVB-T delivery system) to V4L2 API at runtime?
>
> Yes. There are lots of drivers that do that. There are even a few that allow to control the
> frontend and demod via DVB API and to receive streams via V4L2 mmap or read API.

Could you give closest example?
In that case I have RTL2832 DVB-T frontend which I want to change SDR 
mode. What are the those existing DVB frontend drivers look example.

regards
Antti


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