Embarrassing home videos...

[SongsOfDragons]

Hi all, got a techy question this time...

Dad's got a load of embarrassing home videos he's finally managed to put onto DVD, some of which are two decades old, and now we want to make backups.

I've managed to find a programme that will rip the files off the DVD, which was quite easy... the problem is that the resulting hour-long mp4 files are around two gigabytes each, which when I compare it to a similar-length file (an animated movie) is massive! I've tried converting them to .avi, but that doesn't improve the file size much.

I don't know anything about media files, not really. The source media is quite old and I don't know what blah numbers do what...but is there a way to make them smaller?

Thankie

[EricKei]

Is the original source mono instead of stereo, perchance? Or, if stereo, does it really MATTER? you can consider converting the audio to monaural, which will shave off a fair chunk of space. You can also consider reducing the resolution of the videos or compress them, but, by definition, this will lower the quality.

[emax4]

I second that. It doesn't matter. There's no need to get them to a smaller size. Keep in mind that you can use something like Handbrake to rip the DVD and store the file to your hard drive, or in this case, a hard drive for use as backup. If you want you can burn it to another DVD to keep it as a physical backup.

You can use Handbrake to change the size of the video (resolution) to something smaller, so less pixels results in a smaller size, then burn that to a DVD and test it to see if it's acceptable. A DVD will hold 4.7 GB of data. If necessary you can get dual-layer DVDs which double the capacity, but you'll need dual-layer discs and a burner that can do dual-layers as well (most should do this).

With the capacity of today's hard drives and the cost of them going down (solid state drives included), I wouldn't worry about larger file sizes. Something to consider is the format in which you're burning them. Meaning that perhaps you have it on a setting that is resulting in a larger file size.

[SongsOfDragons]

Handbrake is the programme I'm using to rip them, and it's working rather well.

I don't know if Dad intends to send the files anywhere; they're long as well as large. I'm courting a fancy of finding a way to cut a chunk out of one or other of them so I can post it to YouTube...XD

I've no idea what settings to fiddle with to try to get it smaller; they take an hour ish to rip. I'll have a look when I get back to the computer later.

[Chromatix]

Okay, time for a fun learning experience. Video compression is a massive subject, and I get to lead you through the very basics of it.

First let's look at what *uncompressed* video would look like. Typical digitisers for PAL video (which is normal in the UK) produce 25 frames of 768x576 pixels every second, and assign equal bandwidth to the luminance and the colour channels. Thus there are 25*768*576*2 bytes per second, or about 22.1 megabytes per second, or 79.6 GB per hour. Add CD-quality audio on top (176.4 KB/s) and that's just over 80 GB per hour.

So what's coming off the DVD is already compressed about 40:1, which is a pretty impressive compression ratio by normal standards. 2GB/hr corresponds to a total "bitrate" of about 4400 Kbps, which is the type of unit I'll be using from now on. That's a perfectly typical bitrate for a single-layer DVD.

DVDs typically use MPEG-2 format, which includes a video track using the MPEG-2 codec and one or more audio tracks using the MPEG Layer 2 or Layer 3 codecs (the latter is more commonly known as MP3) and optionally multichannel audio tracks using AC3 and/or DTS codecs.

MPEG-2 was specifically designed for DVD and broadcast digital TV, and works well at multi-megabit bitrates for standard-definition video. It is, however, pretty old by now, and more effective codecs are available with take advantage of newer hardware's capabilities. There are also older and much simpler codecs, such as Cinepak, which were designed around the limitations of 1990s "multimedia" computers and have extremely poor compression by modern standards.

For your particular need, to back up a DVD, the obvious choice is to do a straight copy onto another DVD. Or, you could assemble four DVD rips together and place the "disc images" onto a dual-layer DVD-R (which can store 8.4GB), which would allow you to remake any of those four DVDs in the future, using that one disc and the appropriate image on it. Alternatively, you could dedicate a hard disk to backup duties, and simply accept that each hour of DVD will occupy 2GB of it.

Any of those gives you something that you can hide away in a separate location from the originals, preferably in a mild and stable climate (eg. a fireproof safe in the cellar). DVDs are probably more resistant to flood damage than a hard disk, so bear that in mind.

Alternatively, if you really want to have a reduced-size copy for whatever reason, you can tell Handbrake to *transcode* the video while it rips it. You should use one of the newer video codecs (such as H.264) and a newer audio codec (such as AAC), and set a lower average bitrate which will determine the final size of the video. You should be aware that this will always result in a slightly *lower* quality copy, similarly to copying a VHS tape - and doing it repeatedly to the same video will cause further "generational loss" - there's a term to look up in your own time.

The "container" file format has very little effect on file size compared to the codecs and their settings - Handbrake will make an MPEG-4 video file by default (which is technically a variant of the QuickTime format), but alternatives such as AVI and Matroska (MKV) will also work.

Start by selecting the DVD (or the raw rip) as a source, then select the Regular - High Profile preset from Handbrake's right-hand panel. This will automatically select H.264 and AAC as I suggested. Now you should customise the settings - on the Video tab, select "Avg. bitrate" and type 1000 into the associated box. Also select both the "Two pass" and "Turbo first pass" boxes. Then, on the Audio tab, make sure that there is exactly one audio track (delete any extras); set the Mixdown of that track to Mono and the bitrate to 96.

The resulting video will be roughly a quarter of the size of the raw rip, with a total bitrate of roughly 1100 Kbps. Your computer will need to work quite hard to perform the transcoding, so expect it to take an hour in the first instance. Watch the results to make sure they're ultimately acceptable, looking both at fairly static scenes and high-motion ones.

To extract a short segment of a video, I normally use Avidemux. I'm not sure whether this can work with MPEG-2 or MPEG-4 format videos, so you may need to convert it to AVI format first. (The videos I usually edit are from FRAPS, which produces AVIs using it's own specialised codec.) Here you can import one or more complete video files, select segments and delete them (they will not be deleted from the original files, only from the current timeline), or select a segment and export that.

Selecting segments of a video file is somewhat different from word-processing. The procedure is to place the playhead at a point and set an "In" (beginning) or "Out" (end) marker, then repeat for the other marker. The segment between the two markers is then considered selected. You will find yourself seeking and playing and pausing a lot - see if you can also find the single-frame-step controls.

I suggest exporting from Avidemux "as is" (ie. passthrough mode for both video and audio) and then transcoding the result using Handbrake, for conceptual simplicity.

YouTube has special requirements for video that it serves. You can upload in any old format, but if it's in the wrong format, it will get transcoded before anyone sees it - see "generational loss" again. The most significant part of the requirements is: *no* B-frames. You can easily adjust for this in Handbrake - follow the above directions, but then also go to the Advanced tab and set "Max Reference Frames" to 1 and "Max B-frames" to 0.