Quality differences for HD to SD conversion

[Mathew Knight]

Hi everyone.

I am aware of a few different methods of converting HD footage to SD. My own experience has been with 1080 & 720 footage ending up on Digibeta, or DVD.

I know this has been covered in the archives, and i know i need to do my own comparitive tests. But are there some broad categories for quality when using different methods to downconvert footage ?

I have seen people simply do a resize in After effects. HD footage comes in, they resize down to SD pixels, then render out an uncompressed quicktime.

I have also used the 'recompress' function in Final cut to turn 720 into DVCPRO-50.

And I have also used the AJA kona card out to a deck.

So far downconverting on projects I have shot has occured rather randomly (often at motion graphics stage).

I know there are all sort of different technical points that will alter this but are there broad categories of quality ?

eg. Aja kona or similar is best, final cut recompress medium, after effects re-size worst

Or are most of these methods very similar once something is standard definition ?

Any suggestions will be appreciated and when I have a clearer idea I will do some comparitive tests myself.

 

[MikeCurtis]

there's no magic to it, it is all about the algorithm. hardware tends to do it in realtime, but has to be executable in hardware...not always the most sophisticated algorithm. I prefer software solutions, there are lots of them. I haven't done a true test of all options. But Final Cut's Media Manager's Recompress To function isn't bad in the latest versions.