BBC-HD 的 29.97i 视频和 25i 视频之间的联系

之前在做《Wild China》的时候曾经在网上看到有人质疑 Blu-ray 版本的视频帧率是 29.97i。因为,理论上来讲,BBC-HD 的播出帧率应该是 25i(PAL)。有人怀疑 BBC 在制作 Blu-ray 的时候做了一些不必要的转换,而且担心画质会有所下降。

今天上网搜了一下相关文章,偶然发现 BBC Post Production 的网站,里面有这么一段话:

There are a large number of international broadcasters involved, with many different scheduling requirements which need to be met, which adds to the challenge. Plus there are different international standards which BBC Resources needs to deliver to, for example 29.97 frame HD to the US and Japan and 25 frame HD to Europe. BBC Post Production, part of BBC Resources, is using its brand new Snell and Wilcox Alchemist Ph.C – HD frame rate standards converter to make this possible. BBC Post Production was the first facilities house in the world to take delivery of this new technology and invested further in it by designing a system to support Dolby E conversions. It has already used the Alchemist on a variety of BBC programmes such as Planet Earth, Galapagos, Bleak House and Nureyev for worldwide sales, as well as Live Earth.

大意就是,BBC 为了照顾北美观众,由 BBC Post Production 工作室专门把帧率从 25i(PAL)转换成 29.97i(NTSC)。而且,他们用了一个貌似很专业的软件,据说还是行业第一。

这下可以放心的压制《Wild China》了。虽然说转换帧率的时候肯定会有画质损失,但是这毕竟是 BBC 官方用这么 NB 的工具做出来的,所以还是信得过的。