Originally posted by Duke_Nukem:

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You can't always convert recorded digital TV streams to DVD, even if they are both MPEG2, without re-encoding.

An MPEG2 stream, as used in the UK's "Freeview" and on video DVD's, consists of an 'I' frame (a real picture frame) followed by a number of frames that are basically how to tweak that picture to get later frames. Obviously, after a while, the resulting image will degrade as inaccuracies mount up, so after a number of in-between frames another 'I' frame is inserted.

PAL dvd spec is that there should be a real image (I-frame) at least every 13 frames. This represents ~1/2 second and this is good enough for seeking to specific points on the DVD. However, with freeview there are often 40+ frames between each real image, way outside the spec for a DVD. Incidentally 'Outside of spec' doesn't mean it wouldn't work, just that it might not work or may work on one player but not another; also note that the number of frames between each 'I' frame varies during a program, so you might even end up with a DVD plays but then goes funny at certain playback positions.

A second issue is that digital TV often transmits video as 540x576 pixels (I think its 540 - 544?), whilst flags in the stream tell whatever is playing it how they should be resized before display. Anyhow, for PAL DVD it should be 720x576 or 704x576.

One thing though . If you re-encode to DVD at a bit rate that gives 1.5 Hrs per disc, the compression quality will be significantly higher than the original broadcast so you shouldn't notice any degradation of the image.

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