Chroma Subsampling and Transcoding

I was recently asked about the benefits of transcoding AVCHD footage to ProRes 4:2:2 or 4:4:4.

AVCHD uses 4:2:0 subsampling, which is the same as MP4. Transcoding it to 4:4:4 or 4:2:2 won’t give you any more information than you had originally, but it will add less noise, if that makes sense.

The problem with transcoding is that, even if you’re transcoding to a higher-quality format, there’s always going to be data lost in translation. That’s one of the reasons I’ve switched from Final Cut to Premiere Pro … In Premiere, I can use the raw camera files from DSLR and AVCHD cameras like the Panasonic AF100 without having to transcode at all.

If you have no idea what I just said, please watch this video I made a couple of years ago to demystify the subject of chroma subsampling.

For a good example of what this looks like in real life, take a look at the 8:53 mark in this nice comparison video by OneRiverMedia of the Canon 5D Mark III and the Blackmagic Cinema Camera. It clearly shows how increased subsampling negatively affects the ability to key otherwise good-looking footage.

5 Replies to “Chroma Subsampling and Transcoding”

  1. So Alex,
    Say I’m still an old-school FCP 7.0 guy (which, sadly I am), and I’m shooting H264 on my 7D. What would you recommend me exporting out to in order to best be used in FCP without data loss?

    I’ve noticed Apple’s Intermediate Codec looks nearly JUST AS GOOD as ProRes, and for nearly half the file size.

    Feel free to reply here, but I’ll get your answer faster via email!

    Thanks in advance!

    1. Thanks for the comment. ProRes is basically the new version of Apple Intermediate Codec. I use ProRes 422(LT) for everything, and I love it. Even now that I’m working in Premere a lot (which doesn’t require transcoding), I export my final files in ProRes 422(LT).

  2. Alex, I just have the previous generation base Mac Mini and think I remember reading somewhere that an advantage of editing in FCPX using ProRes is that you can get by with a slower computer than other editing programs. Is this the case?

    1. Dan, I have never used FCP X on any system and, frankly, have no desire to! Given how much faster Premiere is in every way though, I seriously doubt FCP X has any advantage over it, regardless of what computer you’re using. For example, in Premiere, you can lower the playback resolution to 1/2 or 1/4 to help the computer chug through complex clips without rendering them.

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