To my ears, the BBC2 test too had bleeps of a sort on the left channel (same rate as current, definitely was not a continuous tone) however compared to this, it was incredibly subdued; there was much less difference in volume between bleeps, so I guess it was not as easy to pick up.
Why do BBC use Test Card J for this rather than test card W? I was under the assumption that all channels on analogue are widescreen these cards.
I hope in years to come we have a chance to see the rumoured HD version of Test card W, I vaguely remember reading somewhere that they rescanned the original photo for it.
Why do BBC use Test Card J for this rather than test card W? I was under the assumption that all channels on analogue are widescreen these cards.
I hope in years to come we have a chance to see the rumoured HD version of Test card W, I vaguely remember reading somewhere that they rescanned the original photo for it.
They rescanned the picture in super-super-duper high-res back when they made TCJ & TCW the first time.
And BBC 1 & 2 Analogue don't broadcast in widescreen. They broadcast mostly 14:9 letterbox in a 4:3 frame (with the occasional thing - mostly films - in 16:9 letterbox in a 4:3 frame. And archive programmes, unlike CBBC, in straight 4:3).
Why do BBC use Test Card J for this rather than test card W? I was under the assumption that all channels on analogue are widescreen these cards.
I hope in years to come we have a chance to see the rumoured HD version of Test card W, I vaguely remember reading somewhere that they rescanned the original photo for it.
Testcard J is designed to test composite PAL distribution (and is 4:3). BBC One and Two analogue are broadcast and distributed in composite PAL (at least in England) TCJ is therefore the correct thing to use for a composite RBS test. It probably has to be inserted well downstream of Pres (which is component) these days.
Testcard W is designed to test component distribution (and is 16:9) and is used within studios to test uncompressed component equipment, and also to compress some aspects of compressed gear.
(Some TCW generators have a subtle animation of the dots on the grey scale boxes to confirm that the signal is live and not a freeze, as digital gear will often freeze the last good frame when a signal is lost)
There is a different signal designed to test motion compressed circuits - but I haven't seen the BBC broadcast it (and they may not be able to use it)
Using an ARCed (aspect ratio converted) version of Testcard W on analogue would not be as useful as testcard J, as it doesn't have the stuff that is useful for testing PAL.
PAL composite and analogue/digital component have different potential faults and are susceptible to different errors - hence the requirement for different cards.
Also - if the interrupted tone had different interruptions on the right and left channels, rather than a constant tone on one channel and an interruption on the other, then it is likely to be GLITS tone. This is designed so that you can uniquely identify left and right legs, and also confirm whether something is mono, stereo ,or out of phase stereo.
Audio wise, the tone sounds as if it's the GLITS tone mixed to the left channel only. The speaking clock was on the right channel only. BBC Two was using a lower pitched tone to BBC One.
