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Old 03-14-2005, 04:03 PM   #1
Digital_Guy
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Join Date: Dec 2003
Location: West Virginia, U.S.A.
Posts: 109
Question QuickTime Formats and Compression Settings - Can Someone (Help) Explain?

I have wondered about this for some time. Can anyone help explain all of the myriad of settings for QuickTime saving & exporting? There are three specific items I have questions about:

* QuickTime Export Formats - What do these various formats mean?
What settings are best, depending on the situation? What are the
"pros" and the "cons" for each of the formats?
(See first attached image)
* QuickTime Compression Settings - Again, what do these settings mean?
What do each of the compression settings offer? When is it good to use
a certain setting, vs. another?
(See second attached image)
Also, related to compression settings - is it possible to export a file with
one of these settings as an MPEG-1 file? I know that MPEG requires the
files to be "MUXED" ... can QuickTime file export, in combination with
one of these compression settings, accomplish this?
* Frames Per Second / Key Frame - This area has puzzled me for as
long as I have known about these specific settings also. I can make
a rough, educated guess between the lower frame rates and the higher
frame rates, understanding that the higher the frame rate, the smoother
the image. But why are there frame rates for "12.5", "23.98", "29.97"
and "59.94"? Do these seemingly arbitrary frame rates have something
to do with the history of the motion picture projector (perhaps relating
to an early limitation of the projection equipment that became a
standard that is still in use today) ?
(See third attached image)
I am not really looking for or expecting someone to write a full reply to this post explaining everything I am asking about (each of the export formats, compression settings and frame(s) per second / key frame rates). What I am looking for, and would perhaps be much better (and easier) is for someone to show me where I can find out and read about all of the things I have in question. It seems to be quite technical in detail ... I would not mind spending some time reading and learning about it. Are there any references on the web? And even better ... is this information covered, in detail, in any books available - aside from the brief summaries that are often mentioned in most books (is there a "QuickTime" book or reference guide published? I remember years ago Apple publishing books with Addison-Wesley ... do they still?)?

One final question, about the QuickTime player specifically ... the QuickTime 2.5 player application offered some playback features that I haven't been able to find in recent versions of QuickTime (one of these offered variable-speed playback, by holding down the "Control" key, and then clicking on the double-arrows to adjust playback speed (forward OR backward ) at the bottom right corner of the window. Do these features still exist in the current version of the QuickTime player? If so ... how are they accessed (what are the key combinations)?

Remember - I'm not looking for someone to give an in-depth explanation on everything that I've asked about, just some references to (hopefully) an in-depth explanation (on the web, or, if possible, a published text).

Thanks in advance for anyone that can shed some light on this subject!

- D.G.
Attached Thumbnails
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Old 03-14-2005, 04:56 PM   #2
DaleCooper
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Join Date: Mar 2005
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I am afraid I can't be of much help but at least I know this: 29.97 frames per second is the frame rate NTSC movies are played while PAL (Europe among others) displays at 25 frames per second. As far as I know, films in cinemas are played at 24 frames per second so I suppose the more the smoother is only valid up to a certain rate.

The export settings in the first picture allow you to export a movie to a number of different formats not all of which are movie formats. You can for example just export the sound of a movie or each frame of a movie to a series of pictures (movie to bmp, image sequence). The movie to movie export possibilities mostly depend on what you want to do with your movie, a quicktime movie for example might be particularly suitable for download or streaming from a web page.

The compression settings again depend on how you want to use the data and with what applications if any they are to be processed further. The choice of compression also determines the resulting file size, if you compress a movie as tiff for example it will basically be just a series of images which will be rather large, though you can compress tiff. But a tiff movie will in contrast to a jpeg2000 or other jpeg format not lose image quality as it provides lossless compression.

In addition to that I think one reason for the huge array of choices in the quicktime player is that it reflects what you can to with the quicktime API when you are developing media applications.

chris
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Old 03-14-2005, 10:22 PM   #3
styrafome
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Actually, there are a couple of main reasons for all the choices. One is that video content and purposes are so varied that one codec can't do them all equally well. Another is that codecs have improved over time, adding new ones that are more effective than older ones, yet the old ones are kept around for compatibility so the list always gets longer. The trick is to match the codec with your purpose and ignore everything that doesn't apply.

For example, the best codec for live action is probably hugely inefficient for animation, and vice versa. Also the best codec for archive storage is probably the worst for end distribution because the files would be too big, while the best codec for end distribution would be terrible for archiving because it would lose so much original source data in the process of crunching it down to DVD size.

Googling around, I found this page that sorta lays out all the myriad tradeoffs for codecs and their settings. If you search more on the Internet, I'm sure you can find more comparison charts.

It really has nothing to do specifically with Quicktime or showing off its API. Any competent video standard must support the standard range of industry codecs in order to let people have the choices they need to get their various jobs done.
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