[Ffmpeg-devel] Macromedia Flash 8

Michael Niedermayer michaelni
Tue Sep 20 11:25:07 CEST 2005


Hi

On Mon, Sep 19, 2005 at 11:20:29PM -0500, Jeff Clagg wrote:
> On Mon, Sep 19, 2005 at 09:57:13PM -0400, Mike Melanson wrote:
> 
> > Trade-offs, my friend. As you observed, the video was nicer (i.e.,
> > bigger and more detailed) and the trade-off is that the data size was a
> > bit larger. Let's run some numbers here. I am working off the Serenity
> > trailers listed here:
> > 
> >   http://www.davestrailerpage.co.uk/trailers_s.shtml
> > 
> > The "full-screen" trailer (what a misnomer) is actually 640x272 pixels.
> > It is ~40 MB. The 1080p trailer is 129MB in a zip file. I have
> > downloaded this once and unpacked it and the unpacked size is not much
> > larger. Let's call it ~130MB. Assume that the files are all video data
> > (which they are not, there is also audio and file overhead) and that
> > they have the same framerate (not sure if this is true). Assuming that
> > 1080p means 1920x1080 pixels, this is the amount of raw data that the
> > codec is processing at the different resolutions:
> > 
> >  640 x  272 =  174080 pixels/frame * 3/2 bytes/pixel =  261120 bytes/frame
> > 1920 x 1080 = 2073600 pixels/frame * 3/2 bytes/pixel = 3110400 bytes/frame
> > 
> > The codec is pushing through almost 12 times as much raw data. Yet the
> > file size is only about 3.3 times as large. Not bad.

since when does bitrate scales proportional to the number of pixels if
the per pixel subjective quality is constant? i rather remember it was approx
sqrt() relation so 12 times -> 3.46...


> 
> I should add that in the few cases I've looked into it, it appears to
> me that the h.264 trailers on apple's site are not taking very good
> advantage of the codec at all. (perhaps relatedly, apple's h.264 encoder
> is complete trash qualitywise.) You could probably beat their quality

i dunno about h.264 but their mpeg4 samples used  a completely broken encoder
(or idiot user) for example they encoded interlaced videos as progressive with
all interlaced encoding features disabled

[...]

-- 
Michael





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