[linux-dvb] [RFC] associating pcr with vcxo

Johannes Stezenbach js at linuxtv.org
Tue Jul 26 11:23:38 CEST 2005


Andreas Oberritter wrote:
> if you have multiple displays and/or Picture-In-Picture decoding, then
> you have to define one PCR per display as master for vcxo control.
> 
> Therefore I propose the following simple interface:
> 
> struct dmx_stc_mapping {
> 	unsigned int clock_num;
> 	unsigned int pcr_num;
> }
> 
> #define DMX_SET_STC_MAPPING _IOWR('o', 51, struct dmx_stc_mapping)

I think the naming is a bit misleading, because in your first
sentence you say that this is about setting the "master for
vcxo control". I.e. (if I get it right) you have one 27MHz
crystal, but two PCR/STC. Obviously the vcxo can be synced to
only one of them, so you have to choose (for PiP usually the
one with the bigger picture).

How about:

struct dmx_vcxo_control {
	unsigned int vcxo_num;	// in case you have more than one vcxo
 	unsigned int pcr_num;	// which PCR to sync the vcxo to
};

#define DMX_VCXO_CONTROL _IOWR('o', 51, struct dmx_vcxo_control)

or maybe DMX_SET_VCXO_SYNC_SOURCE?

Johannes




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