Bit rate, quality of picture, DVD or miniDV tape?

For this year's competition a number of films were delivered on DVD. There is no problem with that per se, but mini DV is always going to be better quality than DVD. So if you want the audience to see top quality films then it's mini DV every time.

Sorry this is a bit technical, but the data rate on mini DV is 25 Mega Bits per second and for DVD the maximum is 8. So DVD is compressed video, and like all compression systems they are a compromise on quality. The higher the bit rate the better and closer to the original footage quality the end result is. Some of the DVD's suffered from 'worms' in areas of plain colours like sky. Let me explain. Any noise on the video in a plain area like sky will be treated as blobs of a subtly different contrast or brightness when encoded. As the noise or picture grain changes from one pixel to another the blob position changes hence the description of worms as the blobs appear to move. You will see this in particular evidence on freeview, where we are treated to a variable bit rate of only 1.5 Mega Bits minimum and 3.5 Mega Bits maximum. Variable bit rate is used to further compress the material as this intelligently looks at the video and allocates less space to talking head shots as opposed to live sport which has more detailed changes from one frame to the next. For the kind of short videos the club makes select constant bit rate and best quality, as the

 DVD can hold 1 hour of video at this setting. Now of course we don't know in some software what 'best' actually means. 8 Mega bits is about the safest maximum you can run the video at; the DVD spec is 9.5 but players often cough and stutter at that. Sound: anything over 192 KBits is fine for Dolby stereo. In systems where we don't know what's being set for you, it could be better to export to the hard drive as a video file and use a third party DVD encoding program that allows you to get at the controls. Don't forget too that its best to burn your DVD at times 4. Its tempting to use times 16 for speed, but I often find the times 16 burnt ones are OK on a computer but no good on set top DVD players, as they can stutter.

 During a recent X-Factor there were Cheer Leaders encouraging us to vote. Unfortunately they had in their hands silver stranded fluffy balls which totally overloaded the freeview encoding system with active/moving detail in the picture. As there was no more bandwidth available for the encoder at the transmitter (Ofcom are demanding broadcasters to use the minimum) the picture broke up into big blocks and we were treated to poor internet old style quality viewing. So you can see getting the right setting for the bit rate is important for a good viewing experience. Even the so called professionals get it wrong these days.