Do I need visa for a long layover in Korea? [duplicate]

As @davidvc references, you would not. Using the Republic of Korea Visa Portal Navigator, a search returns these results (country, Philippines, purpose, short term visit; length, less than 90 days)

Tourist/Transit (General) B-2-1 visa

If you satisfy any of the following conditions, you can travel to or transit through Korea without a visa. You will be able to stay for up to 30 days in Korea.

1) Frequent Visitors : You have entered Korea at least 4 times within the past 2 years, or 10 times in your total travel history. Also, you have never violated Korean laws or overstayed in Korea before.

2) Transit Tourists Travelling to a Third Country
- You transit through Korea on your way to the United States, Canada, Australia, and New Zealand and hold a valid visa (including re-entry permit) issued by the aforementioned countries.
- You transit through Korea on your way to a third country or the country of nationality via direct flight from the United States, Canada, Australia, and New Zealand to Korea after legally staying in these respective countries.

To satisfy the second point, you would need a confirmed onward flight ticket (to the Philippines) for departure within 30 days after entering Korea. [Emphasis mine.]

Before you depart, and depending on your location, you might check with the closest Korean Consulate in Canada: Toronto, Montreal, or Vancouver. For convenience, the link is to the relevant visa information page.

You can enter Korea visa-free for up to 30 days during your transit.

Here's what TIMATIC, a database of visa requirements, has to say (follow the first "For details, click here" link on the linked page):

Korea (Rep.) (KR)

Visa Exemptions:

• Passengers with a visa issued by Australia, Canada, New Zealand or USA to nationals of any country except for China (People's Rep.), Cuba, Iran, Macedonia (FYROM), Sudan and Syria, only if in transit through Korea (Rep.):

  -holding confirmed onward tickets on flights departing within 30 days; when

  -arriving from a third country, departing to the country that issued the visa (e.g. DEL-ICN-YVR); or

  -arriving on a direct flight from the country that issued the visa (a visa that expired on departure from that country is accepted), departing to a third country (e.g. YVR-ICN-DEL).

In order to be exempt from needing a Korean visa, you need to meet the first requirement listed above, the second requirement, and either the third or the fourth.

• You meet the first requirement because you're from the Philippines and hold a valid Canadian visa, or at least one valid at the time of your departure.
• You meet the second requirement because you have a confirmed onward ticket from Korea to the Philippines departing within 30 days of arrival in Korea.
• You meet the fourth requirement because, as you mentioned in a comment, you will be arriving on a direct flight from Canada.

So, you will not need a Korean visa to enter the country during your 16-hour layover.