Re: Quality loss and bitrates

[Nick White] " If I save in the same format (exactly in all respects: file type/codec/version, frame size etc) as I had as a source and at the same bitrate as the source, do I lose quality?"

If the codec is an all I-frame one, like Apple's ProRes or Avid's DNxHD, then there is no noticeable loss in quality in editing and resaving the material. If the codec is a GOP one (h264, AVCHD, etc) and you edit it, the computer has to recreate the GOP structure, effectively decoding and the re-encoding the video stream, which does have the potential for losing quality.

In the UK, most broadcasters are following the BBC's precedent that video is "broadcast quality" if it is (a) 4:2:2 sampled, and (b) 50 Megabits per second or better.

In practice, there is plenty of 35Mbps XDCam in use (plus a fair amount of other formats that are lower than the above spec, e.g., DSLR) and I can't usually tell the difference between that and 50Mbps by the time it's transmitted (things like lens quality, chip size, exposure settings and grading make at least as much difference IMO).

So it's important to keep the number of decoding/encoding steps to the absolute minimum and anything that's originated in a GOP format should be converted to a high quality I-frame one, but it's not necessary to make your material uncompressed. (IMO uncompressed is only really useful as an intermediate if you're going to make copies in various other codecs).