Em 18-02-2011 08:31, Laurent Pinchart escreveu: > It's a trade-off between memory and speed. Preallocating still image capture > buffers will give you better snapshot performances, at the expense of memory. > > The basic problems we have here is that taking snapshots is slow with the > current API if we need to stop capture, free buffers, change the format, > allocate new buffers (and perform cache management operations) and restart the > stream. To fix this we're considering a way to preallocate still image capture > buffers, but I'm open to proposals for other ways to solve the issue :-) >From the above operations, considering that CMA is used to reserve a non-shared memory with enough space for the new buffer size/qtd, I don't think that the most expensive operation would be to realloc the memory. The logic to stop/start streaming seems to be the most consuming one, as driver will need to wait for the current I/O operation to complete, and this can take hundreds of milisseconds (the duration of one frame). How much time would CMA need to free and re-allocate the buffers for, let's say, something in the range of 1-10 MB, on a pre-allocated, non shared memory space? Cheers Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
