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
--
http://palosaari.fi/
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
