Hans Verkuil wrote:
On Saturday 24 October 2009 23:56:24 Sakari Ailus wrote:
Ivan T. Ivanov wrote:
Hi Sakari,
Hi,
On Fri, 2009-10-23 at 13:18 +0300, Sakari Ailus wrote:
[clip]
struct v4l2_event {
__u32 count;
__u32 type;
__u32 sequence;
struct timeval timestamp;
Can we use 'struct timespec' here. This will force actual
implementation to use high-resolution source if possible,
and remove hundreds gettimeofday() in user space, which
should be used for event synchronization, with more
power friendly clock_getres(CLOCK_MONOTONIC).
Good point. I originally picked timeval since it was used in
v4l2_buffer. The spec tells to use gettimeofday() for system time but
clock skewing is causes problems in video encoding.
clock_getres(CLOCK_MONOTONIC) is free of clock skewing and thus should
be more suitable for this kind of use.
I also propose to use timespec instead of timeval.
Hi Sakari,
What is that status of the event API? It is my impression that it is pretty
much finished. Sakari, can you make a final 2.3 RFC? Then Guru can take over
and start the implementation.
Ah.
One thing that I was still wondering was that are there use cases where
other kind of time stamps might be useful? I guess that when the V4L2
was designed no-one though of the need for time stamps of different
type. So are there use cases where gettimeofday() style stamps would
still be better?
In that case we might choose to leave it driver's decision to decide
what kind of timestamps to use and in that case application would just
have to know. The alternative would be to use union and a flag telling
what's in there.
--
Sakari Ailus
sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx
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