Skip subtitle tests if we don't have the codec
Skip subtitle tests if we don't have the codec

Libav does not have the one for movtext.

danielballan/PyAV,PyAV-Org/PyAV,pupil-labs/PyAV,pupil-labs/PyAV,mcpv/PyAV,markreidvfx/PyAV,danielballan/PyAV,mikeboers/PyAV,PyAV-Org/PyAV,mcpv/PyAV,xxr3376/PyAV,xxr3376/PyAV,pupil-labs/PyAV,danielballan/PyAV,mcpv/PyAV,pupil-labs/PyAV,xxr3376/PyAV,mikeboers/PyAV,markreidvfx/PyAV,markreidvfx/PyAV