Guidance Systems: Drugs and Alcohol and Your Choice (Grades 9-12)

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Now, video consumes a huge amount of space, so both DVDs and BDs use lossy compression to make the files smaller. MPEG-2 and MPEG-4 files are the equivalent of MP3 audio files in that respect. And, as you know, "transcoding" from one lossy format to another involves a loss in quality. It's something to avoid if possible, and if not, to do only once. Computers and processors have become cheaper and much more powerful since MPEG-2 was specified in the 1990s. This means we can now use much greater levels of compression to make files smaller, and yet still decode them fast enough to keep up the frame rate. This led to the Blu-ray optical disc format, which mandates support for two new video standards: MPEG-4 AVC (Advanced Video Coding) and VC-1, the latter being based on Microsoft's WMV-9. Some early Blu-ray discs actually used MPEG-2, as that was the basis for digital production at the time. However, H.264/MPEG-4 Part 10 AVC – commonly known as H.264 – is the most widely used format. Fortunately, this usually isn't a problem if you're reducing the movie's resolution – for example, converting a 1080p video to 720p to get a much smaller file size – or viewing it on a smaller screen. It can be a problem if you are "upscaling" a DVD movie to 720p or 1080p. Movies for iPads and iPhones

You don't have much choice if you want to use Apple iTunes and watch movies natively on an iPad or iPhone. Apple makes things simpler by eliminating dozens of popular alternatives (AVI, WMV, DivX, Xvid, FLV, MKV etc) and only allowing two real digital video options: MPEG-4 at 640 x 480 pixels and H.264 at up to 720p on most iPads, and up to 1080p on the iPad mini and iPad Air. Both formats are MPEG-4, so what's the difference? MPEG-4 comes in lots of varieties and H.264 is actually MPEG-4 AVC Part 10. For future-proofing, MPEG-2 files are the next best thing to ISO images, and I don't foresee a time when PCs will be unable to play them. As with MP3 audio files, there are just too many around. The next generation Selected items are only available for delivery via the Royal Mail 48® service and other items are available for delivery using this service for a charge. In defence of Super and Handbrake, I've used them for years and somehow got decent results out of them. I couldn't manage that in my brief trial of Media Coder, though I did get a good conversion in my one go with Xmedia Recode. Also, it may better to use VidCoder rather than Handbrake: it's easier to use and it uses Handbrake to do the transcoding.

With audio CDs, you can use Exact Audio Copy and FLAC, the Free Lossless Audio Codec, to make perfect digital copies that you can leave to your grandchildren, who will be able to convert them to whatever format is popular at the time. With DVDs, you don't get a perfect copy, just a lossy video file, so an ISO is the most future-proof option. However, an MPEG-2 file that matches the original (just in a different wrapper, as it were) is almost as good. If you're going to transcode MPEG-2 into something more modern, then H.264/MPEG-4 AVC is probably the best bet, and the files should be about half the size. Whether they'll be good enough for the 4K (3840 x 2160 pixel) screens we'll all be using in a few years is another matter. The UltraViolet solution Most DVDs store movies in the standard MPEG-2 format (aka H.262) defined by the Motion Pictures Expert Group, though MPEG-1 is also supported. The video is held in VOB (Video Object) files. The video is interlaced for display on ordinary TV sets. The result is a resolution of 720 x 576 pixels at 25 frames per second, for 50Hz TV sets, or a resolution of 720 x 480 pixels at 29.97 frames per second, for 60Hz TV sets. MPEG-2 was the obvious choice for DVDs as it was already being used for broadcast and cable television. The 720 x 480 format came from America's NTSC television system and 720 x 576 from Europe's PAL. ISO or MPEG?