[no] compression question

I have a question concerning the use of no compression.

Say I have that 5 seconds DV clip [Pinnacle states it was a full quality copy]. Now I change some minor things like brightness for compositing reasons and render the clip (exact same length) out with no compression. Why the hell is the rendered file 5 times bigger than the original clip if there's no compression involved? Shouldn't it be about the same file size? Why do I get a 300 MB clip off of a 44 MB one?

 

NO.

If you re-compress it using DV compression, you'll only lower the quality. It might not be much, but after it goes through several more re-renders, it'll look like utter crap on a stick. Yes, the video was compressed to begin with, but in order to maintain quality, you'll have to do the rest of your renders uncompressed. Or at the very least, using a visually-lossless compression format, which amounts to the same thing.

 

That didn't answer my question but let another one arose:

Am I REALLY importing an uncompressed DV AVI to the computer?

 

TigerCraneFist did answer your question.

There's no such thing as an uncompressed DV AVI (or rather, there is such a thing, because "DV" is simply an abbreviation for "digital video", and uncompressed AVIs contain digital video information, but in the way that you mean it - a movie imported from a miniDV camcoder - there isn't).

The camcorder itself compresses the video. To display the video on your computer monitor, your computer uses a DV codec (COmpressor/DECompressor) to decompress the video stored in the AVI. If you subsequently render that video to an uncompressed format, it will naturally give you a larger file size.

As TigerCraneFist says, if you want to maintain the same file size, you must render it using the DV codec.

But, as Jedi2016 says, multiple decompression and recompression o[perations will degrade the quality.

 

uncompressed DV AVI

"uncompressed" and "DV AVI" are mutually exclusive. That means all DV AVI files are compressed with the DV codec.

-Spiff

 

Yes yes. Basically when you choose "uncompressed" for AVI files, your converting the DV AVI to another codec altogether. I like to call it the "uncompressed codec".

Nothing is as lossless or as large in file size as the uncompressed codec. It's great for small clips that you're still working on but should not be used for the final prodcut. For example, the Highlander music video I made (which for some reason no one on this board seems to want to watch and/or comment on ) is in 34 uncompressed parts. All the parts are on a timeline in AE 6.5 Pro. I can then export that to the Micro$oft DV codec and then use that one to convert to my DivX or Sorenson versions (damn AE and it's sucky compression output when using DivX or Sorenson).

 

How can something be more or less lossless than something else?

 

RIPLEY:
1) The data on your DV tape has been compressed in the camera to "DV" codec
Capturing this at "highest" quality or whatever your capture program calls this is "lossless" (no data is changed or "lost") but it is still "compressed", therefore smaller than a truely uncompressed video file.

2) When you render to "non-compressed" you will loose no quality whatsever, since the raw calculated values of each pixel will be written to the new file without changes. Since the DV file was compressed to start with though, your uncompressed file will be larger.

Evil-Henchman :Nothing is as lossless or as large in file size as the uncompressed codec.
Not entirely true.
There are "lossless" codecs that compress data without loosing "information".
You could, for example, store a row of 100 black pixels as "100:black" instead of "black" 100 times and there is no information lost. (this is an ultra simplified example)

FUNK: How can something be more or less lossless than something else?
Basically, most compression codecs get some of their space savings by discarding some information. They try to be "smart" about the information discarded, so that it is barely noticable by a person watching the video under normal conditions.
As mentioned above, there are a few "lossless" codecs that do not discard any information, but these do not compress files as small as "lossy" codecs.

It's generally best to work with either original captures or uncompressed renders until the project is finished, then render compressed versions for final delivery.

Have fun.

 

Oh, I know how compression works, at least peripherally (..spelling, I know..), but 'lossless' suggests a binary state--it's either lossless or it isn't.

 

Okay...

I think I understand now. I still don't understand why something AS lossless as the original DV file naturally gets LARGER. That just can't get in my brain, sorry. But I will accept it.

 

This thread is a well of information for those new comers. It answers a lot of questions regarding CODECS and compression. Bookmarking this so I can send everyone to it.

 

Took me a while to grasp that as well.

I think of it this way:

A DV tape is like a .zip file. DV cameras compress the video and audio data onto the tape, making the data smaller. And DV players uncompress that data in order to play the video back, "unzipping" it in realtime onto the video screen. If you're just watching a tape you're not aware that it's happening at all.

Now... when you scan that tape into your computer and open it as a file in AE, AE also uncompresses/unzips it, and then leaves it that way until you tell it how you want it rendered out again.

So - the DV data was compressed originally, but AE has "unzipped" the data into the size it would have been if the camera hadn't compressed it.

And so, if you re-render the file "uncompressed" it ends up larger than before.

(yes, I'm simplifying. )

 

That really cleared it up for me! Thanks.

So why does the tape compress at all?

 

It's an issue of how much data can be stored on the tape.

It's also an issue of how quickly data can be written to a tape. Uncompressed video is way too big to store much on a DV tape. Also, even with the necessary space (meaning a tape the size of Arkansas), to write all the data needed for uncompressed video, the tape would need to be moving VERY fast and DV tapes can't do that.

 

How does Gerorge Lucas do it?

 

DivX

 

Actually, for the last SW movie, they used a combination of Sony SW-1 and SW-5000 tape decks, and hard disk recorders. Muy costoso.

 

Prohibitively expensive cameras and recording decks, that are insanely way out of our reach. I can't even to beging to imagine the HD space used on the film.