It was early 2002, and I was working for Wuhan Television as a cameraman. One day my colleague, Chen Weijun, the director of To Live is Better Than to Die, told me that he was making a documentary about HIV-affected people in a village. He had been working on the film for more than a year and had quite a lot of footage. He asked me if I wanted to be his editor, and I immediately said yes.

We spent 10 months finishing the editing. We had no idea what to do with the film after we finished. We sent it to compete in domestic film competitions but didn't get any responses. After months of struggling, a former colleague who worked for Voice of America suggested we try the Sundance Film Festival. The film was accepted, and that was amazing!

I had always dreamed of becoming a film-maker. My father was a film projectionist, and later he became the headmaster at a film-projectionist school.

What was it like making documentaries back then?

The heyday for Chinese documentaries was in the late 1990s and early 2000s. One reason was access to digital cameras became much easier and more affordable.

There weren't any real documentaries before. But during the heyday of documentaries, many people who worked for state-owned TV stations felt they had a responsibility to record dramatic changes in society. So they made many powerful documentaries. Still, most were quite raw, and they applied very little storytelling techniques.

Censorship was also tight. HIV was a banned topic a decade ago. National security officers spoke with Chen after we applied to Sundance.

What is censorship like?

It's very hard to make a documentary on the mainland because all levels of government are afraid of media exposure. The guidelines are often very blurry. For example, if the government doesn't like the people backing your film, it will likely be banned. If you attended a film festival they don't like, well, your film will likely be banned.

I suspect the government might be changing its attitude, though. In my case, the authorities contacted me last year and allowed Last Train Home to be shown legally in China. That was quite amazing. I think it was because I had won some international awards, and they didn't want to embarrass themselves. Also, they want to encourage talented young Chinese film-makers to document China and show the world Chinese culture.

Some people think that whoever works with the government will fall victim to the system, but I believe differently. As a director you can always push the envelope. No one is there to tell me what I can do, even though they give permission to broadcast. And if you're smart enough, you can actually push the bottom line.

A bigger problem regarding censorship today is that, after decades of government-imposed censorship, people got used to self-censorship. It's like if I forced you to kneel down for decades, you'd probably forget that you could stand up.

What is the documentary industry like today?

It is still in its infancy on the mainland and it's a bit twisted. The government is pouring money into documentaries, but most of it has gone to state-controlled media. Then they spend money on films that do little to change the reality in the country. It's almost impossible for independent film-makers to get government grants for their projects, which are usually about contemporary topics.

The quality of documentary film-making here sill appears immature when compared with international films. The main reason is a lack of funds. Also, many directors have never had professional training and they lack storytelling abilities. Thus, the film-making techniques of many Chinese documentaries you see today are still rough. This is not to say China has no good documentaries; in fact, there are many powerful and inspiring documentaries making an impact in China and around the world.

Why did you pick migrant workers as the subject of your first film?

Back in my days at CCTV after Wuhan Television, when I travelled, I was constantly confronted by the shocking poverty and misery across the country's vast rural land, buried under the glamour of the modern metropolis. I started to realise that the country's millions of migrants - the very contributors to today's prosperity - have been denied many basic social necessities.

They have to bear this great grief of constant separation from their loved ones. I decided I had to make a film to document this unique group against the backdrop of a changing country.

What are your next plans?

I will keep the focus on migrant workers, and especially the second generation of these migrant workers. They want to change their identity from migrants to urban dwellers, but are Chinese cities ready or willing to embrace them?

The larger picture behind this is the process of urbanisation. I always worry about the future of these young migrant workers. If the cities don't accept this group, will they go back to the countryside? Or could they even go back? Amid a lack of an efficient social safety net, and with the risk of losing their farmland in the urbanisation process, where will their homes be tomorrow?

I want to spend 10 to 15 years documenting the changing fates of China's migrant class, to explore how they impact the future of this nation.

China is like a high-speed train, running fast, with both achievements and problems. No one can be sure where the train is heading, and we are all on board together. What we can do is try to fix all the problems to the best of our ability. You don't have to do a lot, but do as much as you can. And that will help the train stay on the right track and not derail.