[gst-devel] v4l2src, tuner frequency unit

Stéphane LOEUILLET stephane.loeuillet at tiscali.fr
Sat May 29 03:31:02 CEST 2004

hello list,

playing with v4l2src, looking at frequency values for various channels,
i saw that frequencies where strange :

TF1 :  7796 (real freq = 487 250kHz)
FR2 :  8180 (real freq = 511 250kHz)
FR3 :  8564 (real freq = 278 330kHz)
C+  :  3200 (real freq = 200 000kHz)
FR5 :  7540 (real freq = 471 250kHz)
M6  : 12020 (real freq = 751 250kHz)

can't be Hz, kHz or MHz

then i took a look at v4l2 specs, and i saw :

Tuning frequency in units of 62.5 kHz, or if the struct v4l2_tuner or
struct v4l2_modulator capabilities flag V4L2_TUNER_CAP_LOW is set, in
units of 62.5 Hz.

so, the unit is 62.5Hz or 62.5kHz, depending on a property that is not
exported by v4l2src plugin.

what is the better thing to do ?

changing get & set functions to get real frequencies ?
exporting other tuner capability flags to let the user app do it ?

i saw some basic channel/frequency management in v4l2 sources.
what are their state ?
any docs around ?
could they be used for channel discovery/frequency scanning ?


Stéphane LOEUILLET <stephane.loeuillet at tiscali.fr>

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