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Diversity support?

DISCUSSION Luca Olivetti 3 participants 10 messages Oct 17, 2012 – Jun 4, 2013 Media (V4L/DVB)

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#1 lore raw

Al 17/10/12 19:12, En/na Luca Olivetti ha escrit:

Quoted 11 lines

Hello,

if I look at the vl4-dvb wiki, it says that diversity isn't currently supported

http://www.linuxtv.org/wiki/index.php?title=Special%3ASearch&search=diversity&go=Go

however grepping the git tree there are various mentions of diversity at least for some dibcom based devices:

http://git.linuxtv.org/linux-2.6.git?a=search&h=HEAD&st=grep&s=diversity

So, what's the real status of diversity support?

Nobody knows?

Bye

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Luca
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#2 lore raw

Al 31/10/12 19:08, En/na Luca Olivetti ha escrit:

Quoted 7 lines

Al 17/10/12 19:12, En/na Luca Olivetti ha escrit:

Quoted 6 lines

Hello,

if I look at the vl4-dvb wiki, it says that diversity isn't currently supported

http://www.linuxtv.org/wiki/index.php?title=Special%3ASearch&search=diversity&go=Go

Quoted 7 lines
Quoted 5 lines

however grepping the git tree there are various mentions of diversity at least for some dibcom based devices:

http://git.linuxtv.org/linux-2.6.git?a=search&h=HEAD&st=grep&s=diversity

So, what's the real status of diversity support?

Nobody knows?

I'm not easily discouraged :-) so here's the question again: is there some dvb-t usb stick (possibly available on the EU market) with diversity support under Linux?

Bye

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Luca
#3 lore raw
Quoted 12 lines · Luca Olivetti

Al 31/10/12 19:08, En/na Luca Olivetti ha escrit:

Quoted 11 lines

Al 17/10/12 19:12, En/na Luca Olivetti ha escrit:

Quoted 10 lines

Hello,

if I look at the vl4-dvb wiki, it says that diversity isn't currently supported

http://www.linuxtv.org/wiki/index.php?title=Special%3ASearch&search=diversity&go=Go

however grepping the git tree there are various mentions of diversity at least for some dibcom based devices:

http://git.linuxtv.org/linux-2.6.git?a=search&h=HEAD&st=grep&s=diversity

Quoted 7 lines
Quoted 3 lines
Quoted 1 line

So, what's the real status of diversity support?

Nobody knows?

I'm not easily discouraged :-) so here's the question again: is there some dvb-t usb stick (possibly available on the EU market) with diversity support under Linux?

I have feeling AF9035/IT9135 dual devices could do that.

regards
Antti

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http://palosaari.fi/
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#4 lore raw

Al 04/06/13 01:17, En/na Antti Palosaari ha escrit:

Quoted 5 lines
Quoted 3 lines

I'm not easily discouraged :-) so here's the question again: is there some dvb-t usb stick (possibly available on the EU market) with diversity support under Linux?

I have feeling AF9035/IT9135 dual devices could do that.

Looking at the wiki, most devices based on those demodulators are either unsupported or have a dual tuner but not diversity.

Bye

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Luca
#5 lore raw
Quoted 10 lines · Luca Olivetti

Al 04/06/13 01:17, En/na Antti Palosaari ha escrit:

Quoted 5 lines
Quoted 3 lines

I'm not easily discouraged :-) so here's the question again: is there some dvb-t usb stick (possibly available on the EU market) with diversity support under Linux?

I have feeling AF9035/IT9135 dual devices could do that.

Looking at the wiki, most devices based on those demodulators are either unsupported or have a dual tuner but not diversity.

Because diversity is not interesting feature at all in normal use case. Whole DVB-T standard fits poorly for mobile usage and you cannot make situation that much better using diversity.

Dual hardware could support diversity, but it is not usually enabled by software.

regards
Antti

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http://palosaari.fi/
#6 lore raw
Quoted 6 lines · On Tuesday 04 June 2013 13:17:49 Antti Palosaari wrote:
Quoted 5 lines · Luca Olivetti

Al 04/06/13 01:17, En/na Antti Palosaari ha escrit:

Quoted 4 lines
Quoted 3 lines

I'm not easily discouraged :-) so here's the question again: is there some dvb-t usb stick (possibly available on the EU market) with diversity support under Linux?

Quoted 8 lines
Quoted 4 lines
Quoted 1 line

I have feeling AF9035/IT9135 dual devices could do that.

Looking at the wiki, most devices based on those demodulators are either unsupported or have a dual tuner but not diversity.

Because diversity is not interesting feature at all in normal use case. Whole DVB-T standard fits poorly for mobile usage and you cannot make situation that much better using diversity.

Well, I have to disagree on this statement.

Diversity does not do a lot in fixed reception. That's right, but depending on the TV-standard the diversity gain in mobile reception can be enormous.

Several field trials we did in the past years have shown that large parts of the trial route which have not worked at at all in single receiver work like a charm in diversity.

Maybe the route-selection in this cases was biased to show off the performance of diversity ... well, it worked - diversity showed off.

best regards,
--
Patrick

#7 lore raw
In reply to Luca Olivetti
Quoted 7 lines · On Monday 03 June 2013 17:14:18 Luca Olivetti wrote:
Quoted 3 lines
Quoted 1 line

So, what's the real status of diversity support?

Nobody knows?

I'm not easily discouraged :-) so here's the question again: is there some dvb-t usb stick (possibly available on the EU market) with diversity support under Linux?

There is some diversity support hidden in the dib8000-driver and in some board-drivers which use it. Basically it creates several instances of the dib8000-driver (one for each demod) but it exposes only one dvb-frontend to userspace via the API. When the user is tuning the frontend he is, in fact, tuning all of them in diversity.

IMO, the question which needs to be discussed is for diversity-support is an "how to change the API"-question and how does userspace can control it?

In my experience with multi-frontend-hardware, which can do diversity or dual/triple-reception or both at the same time, is that the question is the routing and the grouping of frontend and assigning them to their sinks (stream-interfaces).

Right now DVB-API can expose several frontends and dvrs and demuxes for one device, but there is no way to userspace telling the hardware to combine frontend0 and frontend1 to do diversity.

When looking at diversity/multi-frontend problems, IMHO, we should not limit ourselves to USB-devices. The real usage of those MFE-devices is in an embedded hardware (STB in a car or at home).

--
Patrick

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#8 lore raw

Al 04/06/13 13:23, En/na Patrick Boettcher ha escrit:

Quoted 9 lines · On Monday 03 June 2013 17:14:18 Luca Olivetti wrote:
Quoted 7 lines
Quoted 3 lines
Quoted 1 line

So, what's the real status of diversity support?

Nobody knows?

I'm not easily discouraged :-) so here's the question again: is there some dvb-t usb stick (possibly available on the EU market) with diversity support under Linux?

Quoted 5 lines

There is some diversity support hidden in the dib8000-driver and in some board-drivers which use it. Basically it creates several instances of the dib8000-driver (one for each demod) but it exposes only one dvb-frontend to userspace via the API. When the user is tuning the frontend he is, in fact, tuning all of them in diversity.

Mmmh, but, according to the comment, the dib8000 is isdb-t, I'm looking for a dvb-t device.
My idea is to do something like this

http://www.youtube.com/watch?v=STjQBE3BIYM

but using a raspberry pi instead of a windows pc. Unfortunately, the terratec uses the dib0070 (as do most other usb sticks with diversity), I see some fields for diversity in dib0070.[hc], but every report I see it says that it just exposes two frontends and it doesn't support diversity.
Of course I can buy a ready-made car tuner, but what's the fun in that? ;-)

Bye

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Luca
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#9 lore raw

Al 04/06/13 16:33, En/na Luca Olivetti ha escrit:

Quoted 2 lines

Unfortunately, the terratec uses the dib0070 (as do most other usb sticks with diversity), I see some fields for diversity in dib0070.[hc],

s/dib0070/dib0700/ (sorry), though the corresponding driver has the same fields about diversity

Bye

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Luca