This is YHT(Yüksek Hızlı Tren-High Speed Train). The Ankara-Istanbul line is opened in 2014 but as some tunnels in Doğançay and Vezirhan are not opened, the train uses conventional line from Istanbul to Arifiye. Because of that, the 533km route takes 4,5 hours.
Definitely not a competitor to airplanes. This route takes 45 minutes using airplane. I was on the car no.1 (Business Class) on the seat 2C.
The video is long enough to enjoy every moment of the journey and short enough to watch continuously. If you're not happy with it, here's the timeline:
00:00 - Important info
00:29 - Embarking
01:20 - Departure
02:35 - Arriving at Gebze
03:59 - Awesome view of Gulf of Izmit
04:17 - Food
05:03 - Hitting 250km/h for the first time
06:09 - Arriving at Arifiye
07:42 - Doğançay conventional line
09:06 - Hitting again 250km/h before Eskişehir
09:35 - Restrooms
12:48 - Arriving at Eskişehir
15:55 - Arriving at Polatlı
16:24 - Suburbs of Ankara
17:53 - Arriving at Ankara
Important note: Watch in 50fps! It really improves the experience.