Debugging and Tracing
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## 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.

The NVIDIA VDPAU driver can emit some diagnostic information when an error occurs. To enable this, set the environment variable VDPAU_NVIDIA_DEBUG. A value of 1 will request a small diagnostic that will enable NVIDIA engineers to locate the source of the problem. A value of 3 will request that a complete stack backtrace be printed, which provide NVIDIA engineers with more detailed information, which may be needed to diagnose some problems.

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