[MEncoder-users] Experiences of video encoding

[Kevin Downey]

On 3/26/07, Mathieu Monnier <manao at melix.net> wrote:
> Some random thoughts/questions:
>
>   * Quantizer scales in XviD/lavc and x264 differ. Going from 1 to 51 by
> step of 2 in x264 is fine, but doing so in mpeg4p2 isn't, because the
> quantizer scale is too coarse around 1. I would do 1, 2, 3 and 4, then
> by step of 2 till 16, then by steps of 4 or more. You'll do less tests
> that way, and the RD points will be more smoothly spread along the RD curve.
>
>   * As Corey pointed, P/B quantizer offset is really important. You
> should at least use the same for XviD and lavc. For x264, the default
> one is good.
>
>   * Why do you denoise the video ?
>
>   * for XviD, I don't know if trellis & chroma motion are enabled by
> default. If not, you should do so.
>
>   * XviD should be better, PSNR wise, for h263 quantization type.
>
>   * The cartoon option is - as its name says - for cartoon/anime
> content. It favorizes the skip slightly. It has been implemented without
> any regards to metrics, so it's not surprising it doesn't do well in
> your tests.
>
>   * How do you compare PSNR figures with different resolution ? In what
> resolution do you compute the PSNR. How do you conclude that native
> resolution is good up to 25, then resolution should be lowered ?
>
>   * Your plots are mostly unreadable ( too many curves, not enough
> colors ), and hard to visualize in Firefow, imho ( the original size is
> too small, and zooming prevents you from seeing the big picture ).
>
>   * What does the curves PSNR HD/native size try to show ?
>
> Regards,
>
> Mathieu
>
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you can right click and select "view image" on the graphs, they are
infact pretty slick little interactive svg deals

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