Dakin-West Reaction.....

Solo, like usually I don't have an answer to your main question. Making an aldehyde out of a ketone like that one, in one step, is beyond my knowledge and that Norish photocleavage seams pretty much useless in practice.

The Dakin-West reaction is a ketonization more known to the public in its use as an (in)famous method to form phenylpropan-2-one from phenylacetic acid. But it works better with amino acids since the intermediate oxazolone has the C-H bond much more activated and is thus easily acylated.

Unless you necessarily want to prepare Ph-CH-CH(NHAc)-CHO in no less than two steps and unless it necessarily needs to be an acylamide you might consider using the famous HCOOH/Ac2O formylation mixture that could potentially lead to Ph-CH-CH(NH-CHO)-CHO.
HCOOH/Ac2O forms the mixed formic and acetic acid anhydride (Ac-O-CHO) in situ which acts exclusively as a formylating reagent since the formylic carbonyl is considerably more electrophilic than the acetylic one and thus reacts faster. However, since Ac2O would need to be in excess, chances are that some of the concurrent N-acylation would happen, but the C-formylation of the oxazolone should be nearly exclusive over C-acetylation as it is a more reversible reaction and thus allows for the thermodynamic product to form.
There are little chances that everything works but still it is the only thing I can propose without searching with Beilstein. Aldehydes are much more reactive and prone to polymerizations and other unwanted reactions, but it might nevertheless work.

PS: Wasn't there already a thread with this exact topic somewhere?