Johannes Stezenbach wrote:
On Wed, Feb 15, 2006, Patrick Boettcher wrote:
On Tue, 14 Feb 2006, Mauro Borghi wrote:
Do you know about LinuxDVB-supported devices which are known to support
hierarchical modulation?
Is it meant to be sufficient setting HIERARCHY_2 in the struct passed to
the frontend device when tuning, in order to select the LOW priority
stream?
Although it was most likely never tested with most of the demod-drivers in
linux-dvb it should be possible with all of them.
>From the tests I did with a Twinhan 7045 USB2 clone (from digicom), the
device seems to always lock on the HIGH priority stream, no matter what
params are passed!
The Twinhan box has a MT352 inside and the controlling is done inside the
FX2 USB firmware. As hierarchical transmission has significant drawbacks
when used and no one (not even Twinhan :) ) expected that to be used
anywhere, they don't have it implemented. Ie. there is no way to give this
information to the firmware.
It seems to me that a parameter is missing in the Linux DVB API
to select between the high/low priority stream. If I understand
it correctly the hierarchy mode just modifies the modulation scheme,
and you still need a seperate knob to select which TS (high or low)
the frontend should output. Can someone confirm this?
Yes..
I so, an easy way to fix without breaking API binary compatibility
would be:
typedef enum fe_hierarchy {
HIERARCHY_NONE,
HIERARCHY_1,
HIERARCHY_2,
HIERARCHY_4,
HIERARCHY_AUTO
HIERARCHY_1_LP = HIERARCHY_1 | 0x100,
HIERARCHY_2_LP,
HIERARCHY_4_LP,
HIERARCHY_AUTO_LP
} fe_hierarchy_t;
And of course frontend drivers would need to be fixed to handle this.
Yeah, it looks good.
Manu
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