Alan Cox wrote:
> > In particular, will it have the video frame timestamping feature of v4l2 so
> > I can capture video and sound with accurate audio sync?
>
> Yes. There needs to be some thinking here - it wouldbe nice to have the same
> timstamping api available on the audio too so you can tally stuff.
Linux should have a multimedia clock. I would like something similar to
the Unadjusted System Time (UST) of SGI systems, a 64-bit signed integer
that counts nanoseconds. For multimedia you need a clock that counts
monotonically upward, and that cannot be set. The time-of-day is not
appropriate because a call to settimeofday would mangle any capture in
progress.
http://reality.sgi.com/cpirazzi_engr/lg/time/intro.html
I started to move in this direction with V4L2, using __s64 for a
timestamp type, but never took it as far as to release a UST-like API
for Linux. The TSC of various modern CPUs is an obvious choice for a
timebase.
The obstacle is adding the new timestamping to all the relevant drivers
and APIs.
Bill.
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