On 12/12/2013 06:22 PM, Antti Palosaari wrote:
> Hi Hans!
>
> On 12.12.2013 09:55, Hans Verkuil wrote:
>> On 12/12/2013 12:54 AM, Antti Palosaari wrote:
>>> Add V4L2_TUNER_CAP_1HZ for 1 Hz resolution.
>>>
>>> Signed-off-by: Antti Palosaari <crope@xxxxxx>
>>> ---
>>> include/uapi/linux/videodev2.h | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>> index 6c6a601..1bac6c4 100644
>>> --- a/include/uapi/linux/videodev2.h
>>> +++ b/include/uapi/linux/videodev2.h
>>> @@ -1349,6 +1349,7 @@ struct v4l2_modulator {
>>> #define V4L2_TUNER_CAP_RDS_CONTROLS 0x0200
>>> #define V4L2_TUNER_CAP_FREQ_BANDS 0x0400
>>> #define V4L2_TUNER_CAP_HWSEEK_PROG_LIM 0x0800
>>> +#define V4L2_TUNER_CAP_1HZ 0x1000
>>>
>>> /* Flags for the 'rxsubchans' field */
>>> #define V4L2_TUNER_SUB_MONO 0x0001
>>>
>>
>> I was wondering, do the band modulation systems (V4L2_BAND_MODULATION_VSB etc.) cover SDR?
>
> There is no such modulations defined for SDR hardware level. SDR
> demodulation is done by software called DSP (digital signal processing)
> in host computer.
>
> In ideal case, SDR receiver has only 1 property: ADC (analog to digital
> converter) sampling rate.
So in that case the band modulation would be 0, right?
>
> But as digital signal processing is very CPU intensive when sampling
> rates are increased, there is very often RF tuner used to down-convert
> actual radio frequency to low-IF / BB. Then ADC is used to sample that
> baseband / low-IF signal and only small sampling rate is needed =>
> stream is smaller => DSP does not need so much CPU.
How does the application know that there is an RF tuner? I assume that
the app needs to know this?
As you can probably tell, I basically know nothing about SDR, so forgive
me if I am asking stupid questions. I just want to make sure all bases
are covered when it comes to the V4L2 API.
Regards,
Hans
>> Anyway, I'm happy with this patch series. As far as I am concerned, the next step would
>> be to add documention and I would also recommend updating v4l2-compliance. Writing docs
>> and adding compliance tests has proven useful in the past to discover ambiguous API specs.
>
> I will do these at finally when I drivers and applications are tested to
> be working.
>
> regards
> Antti
>
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