[fobside]

Can someone explain to me or point me to some information on compression calculation for video? I know nothing basically. If I have 5 minutes of DV, can I figure out what settings to use in order to create a certain file size? Does the end file format matter? Right now, when I compress video, I am just guessing what settings to use. I've also noticed through my various attempts, I can't get 2 minutes of DV to look as good in .mp4 format compared to .mov format, but with larger files I have been able to get better .mp4 video.

Thanks for any help.

[fobside]

Bump. Anyone? Any good books you might recommend?

[Uncle Skeleton]

uh...

first you choose a codec (COmpressor/DECompressor). Then each codec has it's own settings. Everyone you ask will have a different opinion of what codec is best, so take this with a grain of salt.

The top video codecs that are far enough along in development to actually be usable are 3ivx, DivX, XviD, Apple's MPEG-4, VP3, Sorenson and Zygo. With slightly better compression but much much worse convenience and playback options, there's Windows Media (version 9 for windows, but I think mac encoders are stuck at 7 and players at 8) and Real Media (don't know or care what the state of this is at). At lower compression but universal playback, there's always MPEG-1.

There will always be a tradeoff between having the latest cutting-edge technology with the best compression, and having lower requirements for playback, encoding and compatibility. IMO the best codec for balancing these is 3ivx. It is very fast for encoding and decoding, and the files are compatible on all modern platforms without modification. It stays competitive while staying within the MPEG-4 Simple Profile, which means that any MPEG-4 decoder can play it, if it's in an mp4 file, which is actually somewhat difficult at the moment. But the windows version is really cool because it allows mov files to be played in almost any application, with aac audio, which is good because QT for windows is not popular to say the least.

Here's the problems with the other codecs.

Divx lives mostly in avi files. Avi files need to be "doctored" or "validated" before playing in quicktime applications. The divx encoder for mac allows you to encode to a mov (quicktime) file, but that can only be played on Windows by the 3ivx decoder. It's a real shame that such a good codec is shot down by a stupid thing like the container format they chose to use (why not mp4!?!?!)

XviD chooses that cutting edge thing I talked about before. the problem with this (and DivX with all it's advanced features on) is that Apple's mp4 parser refuses to open an mp4 file that Apple's codec can't read (Advanced Simple Profile I think is what xvid and divx are up to). So even though the 3ivx and DivX codecs are capable of decoding the xvid bitstream, you can't get QT to open the mp4 file. you can also stick xvid in a mov file and then 3ivx can decode it (I think divx still refuses to even though it probably can, since that's the whole point of mpeg-4. btw, 3ivx, divx and xvid are all mpeg-4 compliant now). Also of note, 3ivx is much faster at decoding 3ivx-source content than xvid-source. obviously

Apple's MPEG-4 is simply not as good at compression (at lower bitrates around 100 K/s and lower, which is really where the other codecs have near-perfect qauality). If you do use this one, there are some tricks. Encode to Quicktime Movie with MPEG-4 as the codec. This gives better quality then exporting to MP4 file. Also set a high number for the keyframe rate, otherwise it seems to make every frame a keyframe.

Sorenson is an older, more field-tested, more professional codec. It can get better than the free MPEG-4 choices above, but to do so you need the pro version which is like $600

I don't know much about VP3 except that it's not very common and not free. but it has it's supporters. go talk to them if you can find them.

Zygo is really more for extreme compression streaming situations. I think it's shareware.

MPEG-1 is roughly 10x worse compression than the various MPEG-4 implementations, but it will play on any computer faster than about 100 mhz, without installing anything extra. that's a big plus.

you might also be interested that ffmpeg (look for ffmpegX) can encode to and from any mpeg variety, for free. The problem is for MPEG-4 it must output an avi file (again, where is mp4?). It has encoders that are compatible with all versions of divx, but be aware that it is not the same as encoding with divx. Also there's a steep learning curve and no documentation. ffmpeg is open source though

The moral is this. All codecs have their strengths, weakness and quirks. Ideally, someone would look at your footage and tell you exactly which codec would be best for each on a case by case basis. I think it's more realistic for you to take a 3 minute sampling with all possible ranges of lighting, action, color and style, and run it through each of the available codecs and see which you prefer. Then use that for everything. Once you decide on one, you WILL have lots of questions about the settings for it. you will want to go find a board that focuses on that codec (divx, 3ivx, and apple each have their own. I don't know about the others)

[dampeoples]

Do a search here, demonhood did a comparison of filesize/quality in an old thread. Not all of the codecs are covered, but if you are doing testing, he's done most of the work for you

[Nap]

Not sure where you got the idea that On2VP3 is not free. It was released by the Duck Corp as Open Source a couple years ago and is now being developed by the http://www.theora.org/ folks, the ones responsible for Vorbis audio. They plan on releasing a version of VP3 in September that will also include the Vorbis audio.
Not sure if it still is but a year ago VP3 was part of the component download feature of QT 5 and 6.

[scottiB]

Originally posted by dampeoples:
Do a search here, demonhood did a comparison of filesize/quality in an old thread. Not all of the codecs are covered, but if you are doing testing, he's done most of the work for you

That would be here (from 2001):

http://forums.macnn.com/showthread.p...ht=compression