The Chinese are coming. Samsung is steady. Apple's iPhone 7 has to impress

This week's launch of Apple's latest smartphone comes in an unfamilar period for the company - one of falling sales and declining revenues

Wireless-only headphones? Dual rear cameras? Pressure-sensitive sensors? This year, as every year, the Bill Graham Civic Auditorium in San Francisco will be crammed to the rafters with press and Apple well-wishers waiting for the pomp, circumstance and technical revelations of another iPhone launch. But this one, on Wednesday, is more important for Apple than it has been for a while.

After the huge success of 2014's iPhone 6 - which introduced a completely new design with larger screen sizes, attracting more people switching from rival Android phones than ever before - 2015's iPhone 6S has been a bit of a damp squib in terms of consumer buzz. And encroaching competition from China means Apple faces arguably the most competitive market conditions it has ever seen.