Hi Laurent, --- On Thu, 7/22/10, P F <[email protected]> wrote: > > Also, without this workaround in place, I was able to > extract two copies > of a JPEG via two methods: > 1. Through my application > 2. Through an in-line hardware USB analyzer > > > I've attached the two JPEGs mentioned above. > While debugging further, I realized that the 32-byte chunks might not be random data at all. I extracted the previous JPEG in the test stream, and lo and behold, the two corrupt 32-byte chunks were in fact duplicated from this previous frame.
I thought that this duplication implied a dirty cache in the frame buffer,
so I tried a few changes before finally landing on this:
Adding:
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
to uvc_v4l2_mmap. This resolved the corruption. gspca_zc3xx has the same
issue, and this patch worked there as well.
I don't know if this is The Right Way to fix it, but hopefully it gives you
a good clue.
Best Regards
<<attachment: previous.jpg>>
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