Decoder options
Libavcodec options
IDCT
MPEG videos are encoded using certain DCT algorithms. IDCT is the inverse process of DCT. The IDCT algorithm must match the one that was used to encode the video. If libavcodec's auto detection fails for some reason, the proper IDCT can be selected here manually.
Number of decoding threads
MPEG-1/2 and H.264 decoders are multithreaded and thus benefit from multi-core CPUs. The number of cores is automatically detected during ffdshow setup but can be configured here subsequently.
Workaround encoder bugs
When set to “Autodetect”, libavcodec tries to work around various encoder bugs automatically during decoding. Since this is not always possible, specific workaround methods can be selected manually instead.
Soft telecine
Detect soft telecine and average frame durations
Unless your output device is a interlaced TV, keep this checked. Some movies may have alternate frame duration (2:3) due to telecine. With this option enabled, ffdshow averages frame duration for smooth playback.
Beginning with revision 4284, this option is automatically disabled if 3:2 pulldown is being applied in the AviSynth filter.
Trade quality for performance
Drop frame on delay
This option defines a threshold after which ffdshow will start dropping frames to get audio and video back in sync. Out-of-sync issues usually occur when the CPU can't manage its workload.
Skip H264 deblocking on delay
With this option enabled, ffdshow will skip the H.264 deblocking filter and try to re-sync if the video is delayed. Skipping the deblocking filter can decrease the video quality though.
