ipa: raspberrypi: Fix bug in IPA frame drop logic

Fix a bug in the IPA frame dropping (for rate control) logic, where the
metadata for the current context was copied from itself (i.e. a no-op), instead
of being copied from the previous context.

This bug does not occur in normal conditions, only when running with a low
exposure time and unconstrained framerate, which happens in a particular
picamera2 test.

Fixes: 546154b ("pipeline: ipa: raspberrypi: Use IPA cookies")
Signed-off-by: Naushir Patuck <[email protected]>
Reviewed-by: Kieran Bingham <[email protected]>
Reviewed-by: David Plowman <[email protected]>
Signed-off-by: Kieran Bingham <[email protected]>

Author: naushir

src/ipa/raspberrypi/raspberrypi.cpp

@@ -1062,7 +1062,7 @@ void IPARPi::prepareISP(const ISPConfig &data)
 		 * in helper_->Prepare().
 		 */
 		RPiController::Metadata &lastMetadata =
-			rpiMetadata_[ipaContext ? ipaContext : rpiMetadata_.size()];
+			rpiMetadata_[(ipaContext ? ipaContext : rpiMetadata_.size()) - 1];
 		rpiMetadata.mergeCopy(lastMetadata);
 		processPending_ = false;
 		return;