use sequence size rather than last frame size when declaring av1 pids - cf #1747
use sequence size rather than last frame size when declaring av1 pids - cf #1747

rbouqueau/gpac,rbouqueau/gpac,gpac/gpac,gpac/gpac,rbouqueau/gpac,gpac/gpac,rbouqueau/gpac,rbouqueau/gpac,gpac/gpac,gpac/gpac,rbouqueau/gpac,gpac/gpac,gpac/gpac,gpac/gpac,rbouqueau/gpac,rbouqueau/gpac