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Maybe not a RBR test, but I remember a really trippy test transmission sometime in 1992 or 93 which was shown simultaneously on BBC2 and C4. I seem to remember it was in widescreen, and featured all sorts of geometric patterns, animated and sliding colour bars and spinning discs, cycling colours and rotating crossed lines. This was set to some really bizarre (but mesmerising) trance-like instrumental music. One thing I remember in particular was the dot-matrix caption overlaid onto this, reading "Engineering Test Transmission" followed by either "Camera Mode" or "Film Mode". The test toggled between the two modes, where the latter was - you've guessed it - filmised.
Those were PAL Plus test broadcasts. As I understand it primarily to see how the transmitters would cope with the PALPlus helper signal that contains 'blacker than black' signals. The conclusion was that some of the BBC2 klystrons couldn't handle the signal, but C4's Tx network (that was of course newer) had fewer problems. That's one of the reasons why the Beeb never pursued PALPlus.
Many parts of it looked similar to MPEG test animations, and I do wonder if it was indeed testing compression. I remember in 92/93 seeing what looked like compression artefacts on C4 (but never on BBC2), but different to the sort we see with MPEG today. In particular, scrolling credits often set off a brief white 'spark' against the edge of some of the text - but always in one spot only - but just about every programme had one instance of this. I also spotted that where credits were on a plain black background, I could see pixellation-and-hold artefacts on that background - i.e. there appeared to be temporal encoding going on even then.
There were problems with the codecs on C4's network distribution system that BT brought on line from Jan 1993. The white flashes were indeed artefacts introduced by the codecs. There was also some subtle problem with the D-SIS/NICAM too, but I can't remember the details.
Mark Boulton posted:
Maybe not a RBR test, but I remember a really trippy test transmission sometime in 1992 or 93 which was shown simultaneously on BBC2 and C4. I seem to remember it was in widescreen, and featured all sorts of geometric patterns, animated and sliding colour bars and spinning discs, cycling colours and rotating crossed lines. This was set to some really bizarre (but mesmerising) trance-like instrumental music. One thing I remember in particular was the dot-matrix caption overlaid onto this, reading "Engineering Test Transmission" followed by either "Camera Mode" or "Film Mode". The test toggled between the two modes, where the latter was - you've guessed it - filmised.
Those were PAL Plus test broadcasts. As I understand it primarily to see how the transmitters would cope with the PALPlus helper signal that contains 'blacker than black' signals. The conclusion was that some of the BBC2 klystrons couldn't handle the signal, but C4's Tx network (that was of course newer) had fewer problems. That's one of the reasons why the Beeb never pursued PALPlus.
Mark Boulton posted:
Many parts of it looked similar to MPEG test animations, and I do wonder if it was indeed testing compression. I remember in 92/93 seeing what looked like compression artefacts on C4 (but never on BBC2), but different to the sort we see with MPEG today. In particular, scrolling credits often set off a brief white 'spark' against the edge of some of the text - but always in one spot only - but just about every programme had one instance of this. I also spotted that where credits were on a plain black background, I could see pixellation-and-hold artefacts on that background - i.e. there appeared to be temporal encoding going on even then.
There were problems with the codecs on C4's network distribution system that BT brought on line from Jan 1993. The white flashes were indeed artefacts introduced by the codecs. There was also some subtle problem with the D-SIS/NICAM too, but I can't remember the details.
