Clearly, the Blu-ray sets of classic Doctor Who are underway and this writer – from a technical point of view – is a little at odds as to whether BBC Records and Tapes (or whatever they’re called now) have embarked on this venture too early. Let me explain…
Please note: this isn’t any in-depth analysis, but an overview (with a generous helping of opinion) to give a general idea.
A Bit of Background
In ye olden days, BBC television drama was recorded in two mediums: video tape and/or film. Shows like Doctor Who, Juliet Bravo, Blakes 7, and most sitcoms would traditionally have a mixture of both. Generally – but not exclusively – videotape would be used for studio and film for locations and model shots.
This was gloriously pointed out during the Monty Python sketch, The Society for Putting Things on Top of Other Things: “Gentlemen, I have bad news. This room is surrounded by film!”
Alternatively, other dramas would be completely recorded on film (Edge of Darkness, Shoestring, Bergerac) but Doctor Who was never afforded this luxury apart from the famous incident where Spearhead from Space was captured all on film, due to industrial action within the BBC.
Of course, the trend can be bucked: The Sontaran Experiment is shot completely on location and it’s captured entirely on video tape. On the opposite side, there are filmed inserts of studio-based scenes, such as Sarah Jane Smith’s daring escape from the rocket silo in Genesis of the Daleks.
When watching programmes from those days, I prefer filmed dramas as I always felt film gave a better atmosphere – take any 1970s A Ghost Story for Christmas – and it would make a production look more expensive; sets did tend to be a bit simplistic and film would be very kind to them.
I have to stress that this is a personal preference as videotaped programmes have their fans too; I’ve had a few heated encounters on forums, over the years. I shall not mention Nigel Kneale’s The Stone Tape, in this context, ever again.
What Can Be Used for High Definition?
The more eagle-eyed readers may have already spotted that Spearhead from Space has received a proper high definition release. But Doctor Who was not filmed in HD until Planet of the Dead in 2009. So why is that?
The simple answer is that film captures the detail that videotape does not. It’s the detail that is crucial.
There used to be a bit of a crime-show cliché where a police detective would request to view a CCTV VHS tape and when watching would see a clue; a distant car for example. The detective would then ask the CCTV operator to “zoom in on that” and a clear, pin-sharp image of the car’s registration number would be visible. This was nonsense as there was no way that video tape could provide such detail as it doesn’t have the resolution.
Thus, there are only two mediums that can be true high-definition: a programme captured using HD cameras and good old-fashioned film. But the original film stock has to be used; if a programme was originally recorded on film but all that is left is the broadcast videotape, then that’s the end of that!
This is why many old classic TV series can be released on Blu-ray and be in proper HD: The Sweeney, The Professionals, Thunderbirds, The Prisoner, UFO, Robin of Sherwood (ITV doing very well there) – film was used and the original film stock preserved. Generally, TV used 16mm film, but production could stretch to 35mm as was the case for Thunderbirds.
This is also the reason why vintage classic cinema films can have HD releases. The sci-fi/horror classic Alien has just had an Ultra HD Blu-ray (4 x HD resolution) release for its 40th anniversary!
Mentioning cinema, the Peter Cushing Dalek films (arguably) win the race as the first Doctor Who captured in “HD”.
Just referring back to the Doctor Who Blu-ray box sets for a moment, if there were any surviving original film stock for a particular story – e.g. Sarah’s aforementioned escape scene – it could have been used to create a proper HD sequence. However, I’m not sure how a mix of upscaled standard definition and high definition would be received.
Standard Definition (SD) and DVD
Broadcast standard definition digital television, launched in 1998, is encoded using MPEG2 which is a codec for video much like MP3 is for music. MPEG2 is the same standard used with DVD.
Codecs are used to compress the raw footage to a data-rate that can be fitted to an allocated space.
Terrestrial broadcast television will have a limited space or bandwidth (Satellite and cable can accommodate more) which will only allow so much. Effectively, this is how much data can be transmitted via the allocated channel ‘pipeline’.
A commercial DVD, on the other hand, has room for 7 gigabytes. Sounds a lot, but the Doctor Who range does fit a lot of extras into those releases. It’s not too bad if the story concerned is only 4 episodes long, but lengthier stories can suffer if too much is crammed on to a single disc.
With a native resolution of 720 x 576 pixels (5:4) or 1024 x 576 (16:9 widescreen), to make an MPEG2 picture look its best, the bit-rate (the amount of data per second) has to be as high as possible, especially for scenes with lots of detail or fast-moving scenes. If the bit-rate is too low, it can result in blocky artefacts especially over movement. Variable bit-rates can be a help here: higher bit-rates for more involved scenes and lower ones for more static scenes.
In the original release of The Green Death, the episodes suffered as the bit-rate was lowered to accommodate other extras on a single disc. This later prompted a two-disc special release to make up for the limited quality of the original.
High Definition (HD) and Blu-ray
It wasn’t until the advent of HD television broadcasts that things really moved forward, in terms of quality, and that all (main channel) output was recorded using high definition cameras.
High definition programmes released on Blu-ray soon followed, although it did take a while to catch up; in some cases, it still hasn’t: the BBC crime drama, Silent Witness has been made and broadcast in HD for several years now, but commercially only SD DVDs have been released.
A commercial Blu-ray disc contains space for 50 gigabytes and can be encoded using a choice of codecs such as MPEG2 or the much more efficient H.264 which allows better picture and a higher resolution at lower bit-rates (which has allowed broadcast HD television).
There is a variation in that there are two main HD resolutions:
- 1920 x 1080 pixels. This is also known as Full HD. This is the standard for Blu-ray.
- 1280 x 720 pixels. When a television is tagged as HD Ready – usually older or smaller screen HD TVs – this is its native resolution. This is also the resolution that the BBC iPlayer uses for its HD output.
Are you still with me? Good. I’ll get to the point soon.
Are There Any Drawbacks to High Definition?
Oh yes! There are things that were not visible in SD that can become apparent in HD.
I was happily watching The Prisoner for years: TV repeats, VHS and DVD… Then I got the Blu-ray set. On my first viewing, I noticed that in a scene outside of No.6’s house, behind the archway next to his front door, there was a very obvious backdrop painting. This is the danger of adding current standards to programmes that weren’t made to be viewed in this manner.
Cinema was made for big screens; pre-late 1990s television was not.
Philip has covered this before, in more detail, in relation to the release of the Paul McGann TV Movie on Blu-ray, but in a nutshell: all Doctor Who stories up to Planet of the Dead that have been released on Blu-ray (except Spearhead from Space) have been upscaled. What this means is that the original standard definition material has been re-encoded with high definition resolution. This does result in a better picture quality (and they look very good) but, as I’ve described above, it is not proper HD. This is why it’s referred to as being upscaled.
Upscaling is also used to describe what an HD or 4K (four times HD resolution) television does when displaying a picture from a DVD player. A DVD’s resolution will be upscaled to fill the television’s native resolution.
Now I’ll get to the point…
I’ve wondered if releasing upscaled SD Doctor Who on Blu-ray was a bit early, from a technical point of view, and I subsequently explained that unless a television programme was recorded using HD cameras or film, proper HD is not possible.
Well… not possible at the moment.
In a past life, I dabbled in converting VHS video tapes to digital video. With the right hardware/software (and enthusiasm) the improvements that could be made to the picture quality were quite staggering! My heyday here was a decade ago and things have moved forward considerably since.
Therefore, I can foresee, in the not too distant future, software and technology being used to convert SD pictures into HD pictures where algorithms will synthesize the missing detail; newer televisions are already making inroads here.
Thus, the answer to the original question – why can’t all Doctor Who be in proper high definition? – is that it most likely can.
Just not quite yet.