Monday 18 March 2013, 09:23
BBC Two HD starts on the 26 March and already several of you have spotted that this means the end of the test card and AV sync test signals.
The test card returned in December 2008 after a long break in a new ’turbo charged’ high definition format along with the brand new AV sync check signal.
The test signal package was added to the BBC HD promotion after we had many complaints about lip sync and ‘odd’ looking pictures. We took some time to have a long look at all the issues and suggestions coming in but we also looked at how the then new high definition televisions were set up when they were delivered.
The biggest issue was definitely lip sync however the complaints suggested we could have up to a four frame audio lead and a two frame video lead – often on the same programme and at the same time!
To get to the bottom of this a colleague from BBC Research and Development (BBC R&D) and I did an end to end sync check of the channel and all its processes. This included a couple of on-air tests to confirm the transmission encoders were not introducing sync errors.
We did find a couple of small problems and after they were corrected I could safely say the system was ‘alright arriving at you’ – a modification of the old engineering phrase ‘it’s alright leaving me’!
The test card and AV sync signal started to go out just before Christmas 2008 and were accompanied by my blog A Christmas Present from HD Channel that included help setting up new high definition televisions and the many (and varied) AV surround systems being attached.
I was very pleased to see a drop in lip sync complaints to virtually zero over the next few weeks. Now whenever we get complaints we can investigate the source, especially when people say they have confirmed their system is correct by using the test signal.
If you want to know more about the tests carried out and the processing involved, the BBC R&D White Paper is worth a read!
The last transmission of the BBC HD Channel promo is actually the morning of the 25 March through to the start of programming later that day. However, after the last programme at around 1.30am on the morning of the 26 (still to be confirmed) and the start of BBC Two HD programmes at 6.30am there is a gap and I made what would be called a ‘land grab’ for the time!
To say goodbye to the test signals we will be transmitting them continuously overnight!
To make it more interesting I have worked with BBC R&D colleagues to recreate some of the older test cards from a 30 line version through the 405 line era, on to 625, colour, widescreen and finally high definition.
I must thank all the current and past BBC R&D engineers who put so much expertise into creating many of these industry standard test cards.
The loop is 10 minutes long so set your PVRs for about a 30 minute recording any time after the last programme (please check the EPGs just in case there are last minute schedule changes) until around 6.00am.
Please remember that the majority of these cards are recreations adapted for the HD Channel and not the originals and also that the HD version is still the modified version which means the grey scale is not exactly correct, but I hope that doesn’t distract from the event.
As for a re-return of the test card I can’t say. Personally I would like to see it again sometime.
Many thanks to all of you who have contributed to the BBC HD Channel blogs in the past but I am sure there will be more blogs about HD and beyond to come.
Andy Quested is chief technologist HD & 3D, BBC Technology.
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Saturday 16 March 2013, 06:00
Wednesday 20 March 2013, 11:58