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TL;DR: my home videos are taking up too much space and are impractical to backup on Dropbox. Which format do you advice to convert them to?

Long version:
One year ago I bought a new compact camera (Canon SX230HS), so I could make nicer pictures and movies of my daughter. While the quality is a big improvement over my previous camera, the filesize of the resulting files also is a lot bigger, especially the movies. In the previous year I produced as much data as in the 8 years before. This is becoming a problem, because I’d like to backup everything on Dropbox, so I'd like to avoid having to backup several gigabytes a month.

I already configured my Canon to shoot in 1280x720 instead of 1920x1080, but this still results in 150 - 200Mb per minute in H.264.
Because those movies are only intended to be viewed by family and friends and posted on youtube/facebook, I'm thinking about converting them to another format. This will obviously lose some quality but I don't think this is a problem, afterall only 10 years ago people where still using tapes for this kind of recording with a lot less quality.

Which format would be best suitable for this? I was thinking WebM, since it seems the results are of rather good quality and because it is pushed by Google I would expect it to have a good change of survival and be recognized.
I'm a big fan of Open formats, so I would prefer the format to be open. But I'd also like it to be as portable as possible. It should be easily playable on most common devices, such as a tablet. (To my surprise this was not really the case on my Google Nexus 7 tablet. When I tried a webm-converted movie on the tablet it had serious problems playing it. I could only get it to play smoothly on the Nexus with the hardware decoder disabled in MX Player.)

Thank you for any advice!

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You'll probably get good advice on how to shrink your files, but there's no getting around the fact that video streams contain a lot of data. You can compress this data in various ways, but there's a limit to what you can do without destroying quality. Forget about storing them on Dropbox, unless you're willing to spend a lot of money. You should look at NAS devices or USB3 disks, which cost about $150/terabyte. – Isaac Rabinovitch Feb 24 '13 at 2:04
While people will disagree with this comment, h264 is open enough for your purposes. You could transcode to a lower bitrate using Handbrake. As for backups, you're better off with Backblaze or one of the other dozen online backups, as it'll get everything, not just your videos. – emgee Feb 24 '13 at 2:46
I'm currently speaking about 30Gb of pictures and movies for 2012. So if I can reduce the video size to about 10% of their original size, I can already backup for a few years on the cheapest Dropbox account. I like Dropbox because it's easy to use on Android and Linux and I already use it. It makes it also very easy to share pictures. Backing up other stuff is not really an issue as most of my other data is already in Git repositories + I have a backup of everything on a NAS. But I want an off-site backup of my pictures as that is something you can never recreate if disaster strikes... – jeroen Feb 24 '13 at 21:19
up vote 3 down vote accepted

I was thinking WebM, since it seems the results are of rather good quality and because it is pushed by Google I would expect it to have a good change of survival and be recognized.

WebM is still inferior to MPEG-4 Part 10 / H.264 in terms of quality. Its encoding mode is resemblant of the MPEG-4 Part 2 standard (known from encoders such as XviD or DivX), which was long superseded by MPEG-4 Part 10—at least in all major applications.

Simply put, and without going into the technical details: You're going to get much better quality and compression efficiency with H.264. This is also suggested by various tests, e.g. this one.

Since the MPEG codecs are the ones the broadcasting industry almost exclusively uses, I'm afraid Google won't play a big role with WebM except for the HTML5 and web market. It's a nice codec and the fact that it's not as patent-encumbered as the MPEG counterparts makes it an ideal choice for the FOSS community, but for hardware vendors, it's easier to guarantee standards-compliency with H.264, for example. This is also valid for operating systems and the default codecs they support, as well as hardware players, phones, etc.

So, to summarize: You're going to get much better compatibility with H.264.

As Jochem Kuijpers said, the successor to H.264 is currently being standardized (HEVC). It'll take a while before the market sees any fast/good encoders though, not even speaking about playback compatibility.

To archive your videos, you should use a constant quality encoding mode (called CRF in the popular x264 encoder). If you just set a constant bit rate, you will get worse quality overall at no real benefit other than knowing which file size you get.

While there are various encoders for H.264—even commercial ones—x264 should give you excellent quality, e.g. with FFmpeg like so:

ffmpeg -i input.mp4 -c:v libx264 -crf 23 -c:a aac -strict experimental -b:a 192k out.mp4

Here, CRF is set to 23, the default. Lower values will give you better quality, and higher values worse quality. Sane values are from 18 to 28. You can use a higher CRF as long as you still like the video quality. I chose AAC encoding with the FFmpeg built-in encoder at 192 kBit/s. There are other choices here, of course.

And that's all there's to it, really. No other settings needed if you're just in for reducing file size. Read the x264 encoding guide and the AAC encoding guide for more options though if you're interested.

See also: What parameters should I be looking at to reduce the size of a .MOV file?

share|improve this answer
Thank you for your excellent answer! After reading the answer by Jochem Kuijpers I started experimenting with ffmpeg and x264. I came to nearly the same conversion-command as in your answer. Except that I'm currently using the MKV container. While both MP4 and MKV play on my Nexus 7 and Samsung TV, I choose MKV so that at least the container is still an Open format. Are there any reasons not to do this? This is the bash command I use: ffmpeg -i $1 -vcodec libx264 -acodec libvo_aacenc -preset slower -crf 23 ${1%.*}.mkv Are there important differences between aac and libvo_aacenc? Thank you! – jeroen Feb 24 '13 at 21:09
No, MKV is absolutely fine if it works for you, but here the situation's similar to the codecs: MP4 is an MPEG standard and (still) has much wider support than MKV. This is likely to change I guess, but it takes time. As for FFmpeg AAC, both aac and libvo_aacenc work fine, however both of them offer bad quality when compared to libfdk_aac or libfaac. You might need to supply higher bitrates to achieve the same quality. For more info see this answer: FFmpeg command to convert MP3 to AAC – slhck Feb 24 '13 at 21:23
I had indeed the impression that MP4 is still more widely supported. While I was considering MKV I did a quick test to convert to MP4 with ffmpeg -i foo.mkv -vcodec copy -acodec copy foo.mp4 which seems to work without any problems and only takes a second, because (if I understand it correctly) that simply copies the audio and video into a new container. – jeroen Feb 24 '13 at 22:06
I just tried the aac codec and to my surprise the resulting file was actually 100kb smaller, even with -b:a 192k. The output of ffmpeg still showed Stream #0.1: libvo_aacenc, 48kHz, stereo, s16, 200 kb/s. Not sure if that is correct. – jeroen Feb 24 '13 at 22:10
Okay, then you got me confused. Yes, the streams can be copied. As for AAC: If your output shows libvo_aacenc, it'll obviously use that encoder. To use the FFmpeg-native aac encoder, you need -c:a aac -strict experimental. But I don't understand what the question is, maybe we're talking about different things? (You can also post a new question if you like) – slhck Feb 25 '13 at 12:13

H.264's being upgraded to H.265. This would allow even greater compression. However, I think that 150/200MB per minute is way too much. If you were to upload a video to YouTube in 720p, YouTube would compress it to about 10 to 15MB/s. Even though YouTube has some experts who tweak their compression so that it would cost them less bandwidth, you should be able to achieve similar quality with 20MB/s and not 200MB/s.

One simple way to convert video's to such a low bit rate but still high quality, would be to upload them to YouTube (and save as a private video). It would also make it easier to share it with your friends. Drawback is that you might experience long upload times...

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