DEBUGGING AND TRACING The VDPAU wrapper library supports tracing VDPAU function calls, and their parameters. This tracing is controlled by the following environment variables: VDPAU_TRACE Enables tracing. Set to 1 to trace function calls. Set to 2 to trace all arguments passed to the function. VDPAU_TRACE_FILE Filename to write traces to. By default, traces are sent to stderr. This variable may either contain a plain filename, or a reference to an existing open file-descriptor in the format "&N" where N is the file descriptor number. The VDPAU wrapper library is responsible for determining which vendor-specific driver to load for a given X11 display/screen. At present, it hard-codes "nvidia" as the driver. The environment variable VDPAU_DRIVER may be set to override this default. The actual library loaded will be libvdpau_${VDPAU_DRIVER}.so. Setting VDPAU_DRIVER to "trace" is not advised.