Universal Media Server | Forum

From mplayer(1):
> harddup
>
> Only useful with MEncoder. If harddup is used when encoding, it will
> force duplicate frames to be encoded in the output. This uses
> slightly more space, but is necessary for output to MPEG files or if
> you plan to demux and remux the video stream after encoding. Should
> be placed at or near the end of the filter chain unless you have a
> good reason to do otherwise.

7.1.12.1. Improving muxing and A/V sync reliability

You may experience some serious A/V sync problems while trying to mux your video and some audio tracks, where no matter how you adjust the audio delay, you will never get proper sync. That may happen when you use some video filters that will drop or duplicate some frames, like the inverse telecine filters. It is strongly encouraged to append the harddup video filter at the end of the filter chain to avoid this kind of problem.

Without harddup, if MEncoder wants to duplicate a frame, it relies on the muxer to put a mark on the container so that the last frame will be displayed again to maintain sync while writing no actual frame. With harddup, MEncoder will instead just push the last frame displayed again into the filter chain. This means that the encoder receives the exact same frame twice, and compresses it. This will result in a slightly bigger file, but will not cause problems when demuxing or remuxing into other container formats.

You may also have no choice but to use harddup with container formats that are not too tightly linked with MEncoder such as the ones supported through libavformat, which may not support frame duplication at the container level.

CustomMencoderOptions = -mc 0 -noskip -vf scale=720:576,harddup -srate 48000 -af lavcresample=48000 -lavcopts vcodec=mpeg2video:acodec=mp2:abitrate=224 -ofps 25