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subego · Mar 26, 2006, 06:15 AM

Title sums it up.

I've found the Apple codec to be wanting, even after tweaking to use the least amount of compression possible (including low GOP lengths).

Thanks!

subego · Apr 16, 2006, 05:06 PM

Figure I'll do one bump, just in case.

memento · Apr 18, 2006, 08:10 AM

I'm not sure of what you're asking. MPEG2 is a codec, so it is what it is. It sounds like you're looking for some kind of noise filter to remove the grain from the original?

subego · Apr 18, 2006, 10:19 AM

Well, I want the codec to more accurately encode the grain, or at least be more visually pleasing with it.

The grain, especially in shadow areas, looks far more like blocky digital noise than grain.

I assume this is just part and parcel with MPEG encoding. The grain effectively means every pixel in every frame is slightly different, which I imagine is not not playing nicely with the keyframe-inbetween encoding method of MPEG.

I am also assuming just what you said, that the choice of codec won't make much difference.

I wanted to check though. It wouldn't be the first time one of my "rock solid" assumptions was made of tissue paper.

P.S. I can't really diddle with the original footage, which is why I'm investigating this rather than some form of grain reduction.

k_munic · Apr 19, 2006, 01:26 AM

Originally Posted by subego

...
The grain, especially in shadow areas, looks far more like blocky digital noise than grain.
I assume this is just part and parcel with MPEG encoding. The grain effectively means every pixel in every frame is slightly different, which I imagine is not not playing nicely with the keyframe-inbetween encoding method of MPEG.
I am also assuming just what you said, that the choice of codec won't make much difference.

any (1/2/4/h264/...) mpeg compressor is a lossy compressor; the goal is to reduce file-size, so you HAVE to loose some information.. as you probably know, a simle way for "crunching" jpegs dramatically is, to add a little blurr (=no grain) before converting - same with mpegs; and grain can be interpreted from the algorithm as "non useful info"...

but, as you can see on commercial videoDVDs, it IS possible to create very convincing results with such a codec (most Hollywood movies have for sure grain); and of course, there ARE differences between the different apps, which create mpeg2 - the codec has a standard, but the way to create it/the algorithms to "calculate" the pictures are very different.

e.g. iDVD uses for material below 60min a very high bitrate of 8kB/sec (that's a little below the max{=9.something} of standards), but a lot of it gets lost for little compressed audio codec, PCM... Toast uses "stronger" audio comression, therefore, the bitrate is more used for video quality.....

"Compressor", as part of DVDSP, allows many manual settings, very elaborate options. = $$$, let me correct that: $$$$

some people say, the mpeg2 algorithm of ffmpeg (done with reverse engineering, so, no license fees to the MotionPicturesExpertsGroup) has some charme, for me too complicated to handle... I get lost in the options....

so, play with ffmpeg, try Toast (you can export the mpegs from there), buy $$$$ Compressor...

subego · Apr 19, 2006, 02:07 PM

Originally Posted by k_munic

buy $$$$ Compressor...

Already there.

AFAICT, I've set things to minimal compression. I'm doing a 2-pass VBR encode at 7.7Mbps, and have the GOP length set down to it's minimum 7 frames... and I'm still getting blocky digital noise.

Is there some setting that I missed?

Uncle Skeleton · Apr 19, 2006, 05:45 PM

increase the GOP length. Or the bit rate; I think it's legal up to 12 Mbps or so in DVD

k_munic · Apr 20, 2006, 01:57 AM

Originally Posted by subego

Already there.

me jealous, you lucky!

Originally Posted by subego

... still getting blocky digital noise.

where do you judge pic quality? hopefully NOT on you Mac's screen... for sure, a computer has a very different way to display video content then a TV... I do use dvd-rW for creating a "quick'n dirty" test-version of my projects (just a few minutes of sample), throw that into my standalone dvdplayer (the good one for 40€) and judge on the telly...

as the Uncle said, make larger GOPs, you burn bandwidth with such small ones... (do some wiki about the deeper meaning of GOP...); AFAIK, Compressor allows the manual setting of keyframes for GOP... try that for "fragile" scenes (low key scenes, dark scenes)...

commercial videoDVDs use 4 - 6b/sec...
.. but for mastering, they do use some elaborated hardware encoders... then you join the $$.$$$ up to $$$.$$$ league

the artifacts also can results of too high contrasts... owning Compressor, means, you own FCP too... play with contrast/brightness settings...

compression isn't a technique - it's an art!!

Uncle Skeleton · Apr 20, 2006, 04:43 PM

Originally Posted by k_munic

as the Uncle said, make larger GOPs, you burn bandwidth with such small ones... (do some wiki about the deeper meaning of GOP...);

It's simple really. You have 4 factors you compromize between: small file size, good video quality, low playback requirements, and fast encoding speed. Large GOP size gives you 1 and 2 at the expense of 3, whereas the parameters you're used to dealing with (like higher quantizers) give you 1 at the expense of 2. In this case, the cost in 3 only affects people who want to scrub through your movie and see every frame, and in general those people can go ahead and buy faster machines.