Many modern devices like TV Tuners, HDV camcorders and IP cams have a Hardware MPEG Encoder.
Different program often install their decoders for MPEG-2/4. You can select the decoders being used for video and audio instead of the default ones.
It will allow you to avoid problems with decoding in case the quality of the default decoders is low. Use the MPEG_Video_Decoder and MPEG_Audio_Decoder parameters to select the necessary decoders.