On 13.12.2013 18:08, Hans Verkuil wrote:
On 12/13/2013 04:42 PM, Antti Palosaari wrote:
On 13.12.2013 16:05, Hans Verkuil wrote:
On 12/12/2013 06:22 PM, Antti Palosaari wrote:
I really appreciate that as simply has no enough knowledge from V4L2 API
and API changes are needed. I will try to list here shortly some SDR
devices in general level enough.
ant = antenna
host = host computer, PC (SW modulator/demodulator)
ADC = analog to digital converter
DAC = digital to analog converter
amp = amplifier
mixer = "TX tuner"
receiver:
ant <> RF tuner <> ADC <> bridge <> host
ant <>ADC <> bridge <> host
ant <> up-converter <> RF tuner <> ADC <> bridge <> host
transmitter:
ant <> amp <> mixer <> DAC <> bridge <> host
ant <> mixer <> DAC <> bridge <> host
ant <> DAC <> bridge <> host
Those are the used building blocks in some general view. ADC (DAC) is
most important hardware block, but RF tuner is also critical in practice.
So what I understood, V4L2 API "tuner" is kinda logical entity that
represent single radio device, containing RF tuner, demodulator and so.
That same logical entity in DVB API side is frontend, which is mostly
implemented by demodulator with a help of RF tuner.
So what is needed is to make V4L2 API entity (tuner I guess) that could
represent both ADC and RF tuner.
Well, a V4L2 tuner represents the hardware that requires a frequency.
Which for typical radio and TV devices means the RF tuner + demodulator
combo. So externally you see only one tuner, but internally there are
often two devices (tuner and modulator) that have to be controlled.
For SDR you have an RF Tuner with a frequency and an ADC with a frequency,
and the two frequencies can be set independently. So representing that
as two tuners seems like a sensible mapping to me.
Correct. Both RF tuner and ADC are independent each others and both must
be possible to adjust runtime.
Shortly, all-in-all, I will implement those as a tuner#0 is ADC and
tuner#1 is RF tuner. Patches with corrections follow soon.
regards
Antti
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http://palosaari.fi/
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