Sorry I'm late in finding this thread, going back to David's post regarding the film "The French Line", according to IMDB this film was released in a ratio of 1.66:1 or, in figures we might use for TV these days, 15:9.
Freeview SD despite being nominally Widescreen format is in fact a 4:3 (or 12:9) ratio picture stretched to 16:9 (rectangular pixels), the Freeview system was designed to accomplish automatic switching of ratios within your TV or set-top box in response to a flag in the digital transmission nominating the signal as either 4:3 or 16:9 as appropriate.
The HD specification, however, is a native 16:9 format (with square pixels) and only ever intended to be shown on a 16:9 screen, any source material not in 16:9 would need to have curtain bars (usually black) added before transmission.
The end result might be subtly different pictures being transmitted.
I've had a look using a BBC internal resource and compared the two transmissions made on 8/8/2013 (SD and HD) and I have to say both appeared to be transmitted in 4:3 ratio.
One possible explanation for the difference David saw might be how David's SD receiver was set to switch aspect ratios on that day such as to overscan a 4:3 picture, the HD receiver would simply show what was transmitted on the HD channel.
Wednesday 6 November 2013 11:08PM
Sorry I'm late in finding this thread, going back to David's post regarding the film "The French Line", according to IMDB this film was released in a ratio of 1.66:1 or, in figures we might use for TV these days, 15:9.
Freeview SD despite being nominally Widescreen format is in fact a 4:3 (or 12:9) ratio picture stretched to 16:9 (rectangular pixels), the Freeview system was designed to accomplish automatic switching of ratios within your TV or set-top box in response to a flag in the digital transmission nominating the signal as either 4:3 or 16:9 as appropriate.
The HD specification, however, is a native 16:9 format (with square pixels) and only ever intended to be shown on a 16:9 screen, any source material not in 16:9 would need to have curtain bars (usually black) added before transmission.
The end result might be subtly different pictures being transmitted.
I've had a look using a BBC internal resource and compared the two transmissions made on 8/8/2013 (SD and HD) and I have to say both appeared to be transmitted in 4:3 ratio.
One possible explanation for the difference David saw might be how David's SD receiver was set to switch aspect ratios on that day such as to overscan a 4:3 picture, the HD receiver would simply show what was transmitted on the HD channel.