#10045 HIGH 1.5-sof: XO-1.5 Record audio/video are out of sync with each other

[James Cameron]

On Tue, May 11, 2010 at 07:30:15PM -0400, John Watlington wrote:
> On May 11, 2010, at 7:24 PM, James Cameron wrote:
> > On Tue, May 11, 2010 at 07:14:53PM -0400, John Watlington wrote:
> >> Writes in UNIX are typically asynchronous --- get the data into a memory
> >> buffer and the program can continue along its merry way.
> >> I strongly suspect that writes through the SD system are forced to wait
> >> for the media to complete the write.
> > 
> > My tests show that our kernel is doing this for USB and SD, on ext2,
> > ext3, ext4, vfat, and raw access to the block device (open ... write ...
> > write ... close).  It isn't doing it for writes to tmpfs or null.
> 
> Are sync writes forced on removable media ?

No.  Most writes pass in a time consistent with caching, and the latency
is so small that I'm certain they aren't reaching the media (60us).
It's only some writes that are delayed by 600ms to 3000ms.

-- 
James Cameron
http://quozl.linux.org.au/