Compressing Large Files

[Gentleman Jim]

There seems to be some very gifted folks on this forum, and I was wondering if you could give me some options to ponder. I want to send my son some movies. They are about 1gb each and in flv format. What is the best way to compress them and how much of a compression ratio could I expect? Is it easier just to send them to him on a DVD? He has a server so I could compress and upload to his server, but would he then need the compression software on his server to 'uncompress' .

Thanks

Gentleman Jim

[Bushfiva]

You should be able to get very watchable video at around 500MB/hour at 512 x 384 or 640 x 352 pixels. That's a tad under 1 Mbps including a stereo channel at 144 kbps (i.e. sampled at 48 kHz).

If you're prepared to reduce the size of the picture, you can save huge amounts of video data. You don't want to drop the sound quality too far because the brain thinks a bad picture with good sound is way better than a good picture with bad sound.

Any H.264-like (MPEG4/Xvid/DivX/Quicktime) format will be pretty good if you're starting from the original source, but since your stuff is already in H.263 (FLV) you may not gain much, if anything, and you may lose a lot of quality very quickly in the transcoding process. In other words, your videos are already compressed courtesy of H.263, and you may not gain much reconverting them to H.264.

You can roughly guess how well encoded a video is by zipping it: if it gets vastly smaller, then the encoder could have done a better job. If it DOES get vastly smaller, I'd simply send the zip version and let the recipient unzip it :-)

[bnt]

I use a program called Handbrake (http://handbrake.fr/) to encode video in to MPEG-4 for my iPod Touch: it accepts FLV happily. It's not the fastest imaginable: encoding a video takes about 20% longer than the video i.e. it's less than real-time conversion, but the quality is good and it's painless. Select a source video, supply a target name, select an output preset, and hit Start.

When compressing video (and audio) the compression will be lossy i.e. it will make the file smaller by throwing some of the data away, and you can choose by how much. That FLV file has already undergone that kind of process, and you'll need to do more of that to make the file much smaller, so be sure to keep the original. Because that kind of data doesn't have much internal repetitiveness, regular "lossless" compression methods such as ZIP don't do much to those files. e.g. FLAC (http://en.wikipedia.org/wiki/Free_Lossless_Audio_Codec) (a lossless compression method for audio) is highly optimised for that job but achieves roughly 1:2 compression.

[spannersatcx]

put them on a usb memory stick, much quicker and easier than messing around converting files.

[Matt.V]

You are trying to reinvent the wheel, gentlemen. Anything lower than 700MB will become unwatchable. 300MB difference. How much time you are going to save - not very much!

Your answer if FTP. There are plenty of open source free clients and servers on the internet. And since your son is running a server he might already have the server - you'll just need a client.

And of course, as mentioned above, sneakernet is always an options where distances allow :p

Edited to add: regarding compression, or rather archiving, since your goal is to reduce amount of data to be transmitted, I'd recommend WinRAR. Way better then any of the competitors. But then again, it costs money so maybe not worth getting your hands dirty.

[A A Gruntpuddock]

I have started using a free service called 'Dropbox'.

2gb free on-line storage available at https://www.dropbox.com/

You can upload your files there then e-mail your son with the name of the folder where they are stored.

He can then access that folder to download the files without also having to join Dropbox.

[mixture]

I would concurr with Matt.V and suggest WinRAR.

Otherwise just reduce the quality of the videos....

[mad_jock]

I would go with the FTP to his server and not buggering around trying to compress things.

If you can get hold of a multi stream with resume function FTP client thats the way I would do it.