In China, gays and lesbians are getting married to have children and to keep parents happy. Successful 31-year-old Shanghai architect Andy is looking for a wife to meet his demanding father's expectations. He attends a speed-dating style "fake marriage market" for people seeking someone who can be a real friend, because it can't be completely businesslike. There he meets Kris, whose mother knows nothing about her. And he worries that an arranged lesbian wife might leave with the child. "If you don't love each other, trust is essential," a parent notes.

The various stories offer different angles. For example, Cherry already has a husband and now wants to adopt a child without coming out as lesbian to her parents. Maybe she can buy an abandoned baby from a local hospital ("but they only have girls, not boys"). The film is beautifully shot in a fly-on-the-wall style, just watching these people cope with their situations. There's no real sense of the relationships between them, and only glimpses of back-stories. Some scenes are shot guerrilla style, such as sessions with a psychologist. And there are also fascinating conversations with parents who pressure them with expectations and criticism.

Most parents know their children are gay but worry about them. As Mei says, "If your father wants you to have a fake marriage, he hasn't accepted you; he went into the closet when you came out." Others get married to hide their sexuality from their parents. Each has his or her own story to tell: kicked out of school for being gay, monitored by the authorities, trying to change because people are so closed-minded, unable to force romance where it doesn't exist. All of them are working to create a life that is unnatural to them.

It's understandable that these people rarely let their guard down on-camera. And it's easy to see the conundrum they face about loving their parents but lying to them (protecting them from the truth?). The point is that all of the pressure comes from the older generation: the younger people aren't able to live their own lives, everything is about their parents. So they're bearing a heavy weight. And the question is whether these people will ever let their children off the hook.

Grant and Jenny decide to only eat expired or discarded food for six months. Their goal is to challenge attitudes and stop wasting so much money on food they won't eat. This shouldn't be too difficult, as fruit and vegetables are thrown out by suppliers simply because they don't look perfect, from 20 to 75 percent of a harvest, even though it's edible. And the mother lodes of perfectly good discarded food they find are staggering. In six months, Grant and Jenny spent less than $200 on groceries and rescued more than $20,000 worth of wasted food.

The question is how to break the pattern in a wealthy society that wants something different for every over-catered meal. American fridges are so big that it's actually impossible to eat everything before it goes off. And over the past 50 years portion sizes have increased in restaurants along with quantities of food items in shops. So perhaps it's no surprise that Grant and Jenny find piles so big they can't take it all, and then start supplying their friends and family.

Through a range of expert interviews, the film explores bigger issues like global importation and the real meaning of sell-by and best-before dates. There's also the fact that wealthy countries have twice the food they need, while the rest of the planet goes hungry. And water embedded in the food we throw out could meet the household needs of millions of people. So wasting food means that we're also wasting a third of our farms. "We are trashing our land to grow food that no one eats," says author Stuart.

The film also explores practical alternatives, starting with the need to stop seeking unblemished fruit and vegetables (shop at a farmers' market instead). Or eat what you have rather than what you're in the mood for. And on a bigger scale, stop throwing food into landfills, which creates greenhouse gasses that contribute to climate change. Instead, food waste can feed livestock and fertilise land. And every supermarket can donate food to people who need it rather than throwing it away. It all seems so simple, and yet our corporate-run world just doesn't care.

A glittering football star both at USC and in the NFL, OJ Simpson was never seen as black by most Americans, breaking into the mainstream as an advertising spokesman and actor. Amid the celebrity, he left his first wife for Nicole Brown in 1977, and over the following years Nicole frequently called police about his physical abuse. They divorced in 1993, and a year later Nicole was brutally murdered alongside friend Ron Goldman. As a wealthy man, Simpson funded a pricey defence that discredited evidence and witnesses. He was acquitted in a case that shocked the world.

More than a story of race, these events encompass America's obsessions with celebrity, violence, sport, commerce and personal wealth. Simpson's story is also about the culture of entitlement and a failed criminal justice system. Edelman fills the movie with telling bookend sequences, such as the polar-extreme of the reactions to the Rodney King verdict and then the OJ verdict, highlighting the deep-seated racial lines running through American society. And of course there's more to the story, as the judicial system finally caught up with Simpson in 2008 and but him behind bars.

Most intriguing is how the film mixes period interviews with present-day ones looking back through the filter of time. It's unusual for a documentary to capture both of these perspectives so sharply, and it adds a complexity that's sometimes difficult to digest. The casual language used back in the 1970s feels shocking today, as does the way it's impossible for us to now think of OJ as the golden boy megastar he once was. And the years after his acquittal and his later arrest for robbery are like something from a bad movie.

The film includes an unspeakably chilling description of the crime, complete with graphic photos. So watching the case fall apart is simply shattering, as it ceases to be about Nicole and Ron, instead becoming a trial, deliberately drawn on racial lines, of the LAPD itself. And the verdict tapped into the national pain, making it a case about American historical injustice. "Now you know how it feels," says activist Danny Bakewell. This is bold, chilling filmmaking that demands a reaction.

US Constitution, 13th Amendment: "Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction."

The USA is home to 5 percent of the world's population, but a fourth of the world's prisoners. How can "the land of the free" have the highest rate of incarceration in the world? Slavery ended in 1865, and it took 100 years until the Civil Rights Act was signed. Then in the 1970s, mass incarceration began under President Nixon, deliberately targeting antiwar protesters and black youth, who were labelled as "predators", whether or not they were guilty of anything. Reagan pushed it further by targeting blacks as drug users. Prison population ballooned from 350,000 in 1970 to 2.3m in 2014. And now 1 in 3 black men are likely to end up in prison for life. For white men, the figure is 1 in 17.

Quick-paced and lucid, the film includes a wealth of historical footage and expert commentary that doesn't let anyone off the hook. Looking back through history, there have been clear efforts to label and control African-Americans, distracting the public with terms like "war on drugs" or "tough on crime", even though these weren't actual issues. In each case, poorer communities have been targeted, for example with exponentially higher penalties for crack than cocaine. And ex-cons now live in a new Jim Crow system without basic rights.

DuVernay clearly traces these issues from the end of slavery to DW Griffith's The Birth of a Nation and the resurgence of white-on-black terrorism, right through the Civil Rights movement and Black Lives Matters. The film is packed with telling observations, such as how phrases like "law and order" were used to incite fear. Or how drug addicts were reclassified as criminals rather than people in need of help. Worst of all were mandatory sentences, which tilted the system so far off balance that prisons can't cope. By contrast, most enlightened countries are closing their prisons.

Indeed, it's the dehumanising prison industry that's the culprit here, namely an insidious corporation-colluding agency called ALEC, which has been behind both law-making and prison-building. The film offers a very wide range of opinions, but the through-line is one-sided, including some hyperbolic comments (like referring to right-wing policies as "genocidal"). But the facts are clear enough to present the case that the overwhelmingly white American legal system has been set up to label blacks as violent and lock them up, whether or not they deserve it, shattering families and communities. This is an urgent, essential document that demands action.