Function ff_request_frame

pub unsafe extern "C" fn ff_request_frame(
    link: *mut AVFilterLink,
) -> c_int

Request an input frame from the filter at the other end of the link.

This function must not be used by filters using the activate callback, use ff_link_set_frame_wanted() instead.

The input filter may pass the request on to its inputs, fulfill the request from an internal buffer or any other means specific to its function.

When the end of a stream is reached AVERROR_EOF is returned and no further frames are returned after that.

When a filter is unable to output a frame for example due to its sources being unable to do so or because it depends on external means pushing data into it then AVERROR(EAGAIN) is returned. It is important that a AVERROR(EAGAIN) return is returned all the way to the caller (generally eventually a user application) as this step may (but does not have to be) necessary to provide the input with the next frame.

If a request is successful then some progress has been made towards providing a frame on the link (through ff_filter_frame()). A filter that needs several frames to produce one is allowed to return success if one more frame has been processed but no output has been produced yet. A filter is also allowed to simply forward a success return value.

@param link the input link @return zero on success AVERROR_EOF on end of file AVERROR(EAGAIN) if the previous filter cannot output a frame currently and can neither guarantee that EOF has been reached.