Re: [Avid-L2] Re: H.264 File Size seems low?

True, true,... I did neglect to mention that, but no applications at the time I experimented with H.264 4:2:2 output could actually open and play the resulting files (even VLC, MPEG StreamClip, and enabling Perian) except After Effects CS5 which could only open and display a distorted view of the file (even FCPX doesn't know what to do with it from what I can see). And this is still true...

Except, I just discovered that After Effects CS5.5 (and AME CS5.5) can open an H.264 high 4:2:2 file. But VideoSpec still sees it as 4:2:0 chroma sampling, so I am a bit confused by that (could be a limitation of VideoSpec). However, doing a quick difference test in After Effects shows that this 4:2:2 file (motion graphics, 720p25, 2Mb/sec) is visually indistinct from the ProResHQ source file (Flatline Waveform). Not that this would make me want to begin using this as an intermediate file format at this time. (And you cannot output an H.264 4:2:2 version from After Effects or AME.) But I can see using it as an archival storage format if it begins to be more generally accepted by player and editing apps.

Episode 6.2 (the most recent update) still has the (4:2:0) H.264 bug they introduced by switching to MainConcept with version 6. Not as bad as in earlier revs, but Compressor is still superior in certain circumstances. A shame really.

James

ps, I don't have Premiere CS5.5 installed so I cannot test that.

On Oct 23, 2011, at 12:47 PM, blafarm wrote:

> >Another consideration is that current implementations of H.264, are still limited to 4:2:0 chroma sampling, and 8-bit color.
>
> I agree that H.264 would not be a preferred codec -- especially with its "baked-in" gamma shift. This shift can be easily viewed by re-importing the resulting H.264 file and comparing it to the source from which it was made.
>
> However, and only for the record, Telestream Episode 6 does allow for the selection of the H.264 "High Profile" -- which provides the following options; 4:2:0, 4:2:2 and 4:2:2 10 Bit.
>
> --- In Avid-L2@yahoogroups.com, James Culbertson <albion@...> wrote:
> >
> > Andi, 4500kbps is completely arbitrary even for 1080/60i. You can stay out of trouble and go quite a bit lower depending upon the content, frame size, frame rate, amount of action in frame, amount of noise,...
> >
> > Depending upon the H.264 video codec supplier (i.e., Main Concept, etc.) you can have access to a number of different bandwidth controls including: CBR, padded CBR, VBR using peak rate, VBR - Quality Based, and VBR using VBV. One application's VBR might render faster than another's CBR.
> >
> > But the main consideration is not necessarily the data rate (if the quality is good), but that H.264 MPEG4 is generally a distribution/acquisition format due mostly to it's inter-frame (across multiple frames) compression which leads to inefficiencies in random access of individual frames (not good for editing). While ProRes and similar use intra-frame compression which is much more efficient for editing. [H.264 also has a highly efficient intra-frame compression implementation, hence Panasonic's AVC-Intra acquisition codec.]
> >
> > Another consideration is that current implementations of H.264, are still limited to 4:2:0 chroma sampling, and 8-bit color. Though the MPEG-4 spec (of which H.264 is a part) supports 4:2:2/4:4:4 chroma sampling and higher bit-depths in theory.
> >
> > James
> >
> >
> > On Oct 22, 2011, at 10:55 AM, Andi Meek wrote:
> >
> > > Bring up the inspector (Apple+I or Ctrl+I). this will tell you the data rate. The lower the data rate, the higher the compression, the smaller the file, what data rate have they used to compress the file? For an HD frame size anything below 4500kbps is asking for trouble. H.264 is VBR I think so it probably didn't save them any time encoding it, it may have taken them more time than if they used a CBR codec like ProRes, especially if they did more than one pass. Likewise if there's lots of noise all over the frame then using Animation wouldn't be a great option either as the run length encoding that animation uses only compresses efficiently if there is not much changing from frame to frame. I would have thought that the best option would have been Prores HQ or completely uncompressed. Ask for it again, they're a graphics company so they should know better and if they don't then they should learn a lesson!
> > >
> > > Cheers,
> > >
> > > Andi
>
>
>
>

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