Tom Metro wrote:
>> ...and whether the "harddup video filter" documented here:
>> http://www.mplayerhq.hu/DOCS/HTML/en/menc-feat-dvd-mpeg4.html#menc-feat-dvd-mpeg4-muxing-filter-issues
>>
>> helps...
>
> I'm not entirely convinced that this filter even did anything, and that
> there was a difference from the prior transcodes I did with no audio
> sync options. One thing that makes me skeptical is that I still saw the
> warnings about skipped frames (same as with no options), and never a
> warning about a frame being added. I also am not sure that mencoder
> applies video filters when you are using the copy codec.
>
> I'll have to test more files, and see if there is any difference in the
> file size between a run with "-vf harddup" and a run without. In theory,
> they should be different.
My test showed:
683241472 2010-04-11 20:13 2061_20100408233000-hard.mpg
683241472 2010-04-11 20:49 2061_20100408233000.mpg
Identical file size suggests the filter does nothing. I couldn't find
anything in the man page or user guide explaining whether filters
applied to the 'copy' codec, but the built-in help text says:
% mencoder -ovc help
Available codecs:
copy - frame copy, without re-encoding. Doesn't work with filters.
So that answers that question.
I don't entirely understand why this is the case, as mencoder should
still be dissecting the stream enough to be able to add frames. This is
implied by its warnings that it is dropping frames.
While doing a video transcode should correct this, I don't know whether
the loss in quality and time needed for the transcode warrant the slight
improvement in sync.
I also experimented with -noskip, -audio-density, -audio-preload, and
dropping the audio bitrate, and none has produced any better results.
I guess I'll have to post to the mencoder user's list to see if someone
with an understanding of mencoder internals can offer advice.
-Tom
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