jpg codec question

i import image sequences into fcp. a while back someone advised me
that maintaining the same codec as the still images use when exporting
quicktime movies would yield the best quality as there would be no
transcoding involved in that workflow. with tga files this is easy as
there is a tga codec option in my export codec list. for jpeg's, however,
i have no jpg option. instead there are three different ones:

motion jpeg a
motion jpeg b
photo jpeg

which is the appropriate one to use for exporting a quicktime movie
from a jpg image sequence? if there is no easy answer to that and any
could be used under varying circumstances, what are the criteria by
which a judgement would be made as to which to use?

thanks,
BabaG

I have not used the motion options but you can use Photo JPEG for your workflow.

I wouldn't want to guess on the deployment criteria for the others. The Big Brothers would kill me if i were wrong.

""" What you do with what you have, is more important than what you could do, with what you don't have."

> > > Knowledge + Action = Wisdom - J. Corbett 1992 """"

Seems to be some confusion here regarding video codecs vs. image sequences. What is it that you want to do?

Export a movie?
Export an Image Sequence?

The only applicable decision criterion here is what you're delivering.

If you're bringing in image sequences to be incorporated into a timeline that will eventually be delivered on (for example) HDCAM SR, then you should convert the sequences into a Quicktime of the same format as your timeline. If you're working in compressed 1080p23.976, then convert the sequences to that format before bringing them into FCP.

to alleviate confusion, this is from the original post:

>i import image sequences

and

>when exporting quicktime movies

and for jeff harrell, what if the delivery is indeterminate? what
if the materials might not be finished for a very long time, or if
they are for archives and the desire is to maintain workable,
viewable video files? the image sequences are not viewable
until they are either rendered or exported. if i spend the time on
rendering, i'd rather spend it on a usable export. that was the
original idea in maintaining the jpg or other still image codec.
wouldn't that be just as good as converting it up front? and in
a case like this, where the delivery format might not even exist
at this time, wouldn't it be a better workflow to export in as
close to a lossless manner as possible, leaving the conversion for
future delivery?

thanks,
BabaG

Quote

what if the delivery is indeterminate?

At the risk of sounding argumentative, then you shouldn't be screwing around with file formats. There are only two reasons to change a file format: because you've gotta take that media into a system that doesn't deal with that file format (like converting to DNxHD for Avid), or because you're converting to an intermediate editing format or final delivery format. If you don't know enough to pick what the intermediate or delivery format should be, then you should just leave the files alone. Because changing them degrades them, and there's simply no reason for doing that. Especially if the original format is something that's as universal as an image sequence. Image sequences have been around since God was a boy, and they're not going to stop being supported any time soon. Hell, digital masters of feature films are stored as sequences of DPX files, and that's intended to be permanent.

You're on the right track when you say that it's sensible to generate intermediates in a lossless format. But the problem is that (a) JPEG is anything but lossless, and (b) going from high-dynamic-range RGB or RGBA image sequences to 8- or 10-bit YUV video files is extremely not lossless.

thanks jeff. this is beginning to get me somewhere.

when i began looking into this i didn't even know it was possible to output a quicktime movie
in what i would consider a still image codec like tga or jpg. i can't realistically leave the images
in their original state, although i certainly plan on retaining them as an archive, since i can't
view them running as an image sequence. that being the case, i have to render them, which
can take considerable time. if i invest that time, i'd like to have the resultant file be as
generally useful as possible. i'd love to be able to simply use it going forward for editing and
exporting.

questions:

regarding "(a) JPEG is anything but lossless," taking jpg images to a 'photo JPG' codec
quicktime export has no possibility of avoiding recompression, of simply copying the images?

related to the first, "(b) going from high-dynamic-range RGB or RGBA image sequences to 8- or 10-bit YUV video files" implies that final cut, or possibly all digital video, only works in the
lower quality 8 or 10 bit YUV colorspace. am i correct in this? it would help me to understand
why, even if going from jpg images to a photo jpg qt file i would be unable to avoid some
kind of transcoding rather than something like a stream copy.

thanks again,
BabaG

Hmmm, Jeff,

I have always thought the scale was:

good - RGB & RGBA
better - YUV 8bit
Best - YUV 10bit uncompressed

In a N.American 0 or 7.5IRE:

10bit = 1024 shades of gray between absolute black and 100% white
8 bit = 256 shades of gray between absolute black and 100% white

More grays mean better chroma and luma

or am i wrong and confusing this?

""" What you do with what you have, is more important than what you could do, with what you don't have."

> > > Knowledge + Action = Wisdom - J. Corbett 1992 """"