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Transcode to ProRes 422 or ProRes 422 HQ when you captured/shot bitrate falls between the two?

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Matt Wilson
Transcode to ProRes 422 or ProRes 422 HQ when you captured/shot bitrate falls between the two?
on Apr 29, 2017 at 1:05:48 am

Hi - I'm curious if some experienced folk have any thoughts on this issue.

Will be editing in FCPX, and grading in Davinici Resolve. I have AVCHD footage shot from a hacked Panasonic GH2 that allowed the bitrate to be approximately 130 Mb/s. I now have to transcode the footage to either ProRes 422 or ProRes 422 HQ. Since transcoding to ProRes 422 typically gives you a file with 117 Mb/s, and transcoding to ProRes 422 HQ usually gives you a file with 176 Mb/s, I want to know if I lose some image quality by transcoding the original higher bitrate 130 Mb/s footage to the 117 Mb/S ProRes 422? Should I be transcoding to 422 HQ to make sure I don't lose image quality?

I had heard in the past that DSLR AVCHD footage doesn't gain much by 422 HQ (vs 422), but I'm wondering if that's because it's typically at a very low bitrate of ~28Mb/s. Since I have my AVCHD at a higher 130 Mb/s, I want to make sure I choose the correct one to transcode to with my goal being the best image quality.

Thanks,
Matt


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Joe Marler
Re: Transcode to ProRes 422 or ProRes 422 HQ when you captured/shot bitrate falls between the two?
on Apr 29, 2017 at 1:16:33 pm

[Matt Wilson] "I had heard in the past that DSLR AVCHD footage doesn't gain much by 422 HQ (vs 422), but I'm wondering if that's because it's typically at a very low bitrate of ~28Mb/s. Since I have my AVCHD at a higher 130 Mb/s, I want to make sure I choose the correct one to transcode to with my goal being the best image quality."

See my other post. You likely don't need to transcode at all. Just use EditReady to rewrap (not transcode) the AVCHD content before import. That preserves the full bit rate of the original content. Internally, FCPX always works on a ProRes buffer, so essentially it's always editing ProRes. Transcoding to ProRes before or after import is mainly a performance issue, not an image quality issue. On a good machine and with 1080p content you normally don't need to transcode to ProRes. With H264 4k, proxy or optimized media is more commonly needed.

If you are doing heavy multicam or if your machine is *very* old or slow, then transcoding to optimized media or proxy might help editing performance -- even for 1080p. You don't need EditReady for that, since FCPX can do that either during import or afterward.

First try to rewrap (not transcode) with EditReady, then import with "leave files in place", and don't create proxy or optimized media. Evaluate the performance. If it's not sufficient, have FCPX either create proxy or optimized media during import or afterward. Proxy is 1/4 res, so not that big. Optimized is several times larger. To use proxy the viewer must be set to proxy, then set back to optimized/original before final export, else the exported files will be at proxy resolution.

Never, ever remove AVCHD files from the bundle and import with "leave files in place". This can cause significant performance problems. If the files are already removed from the bundle, they should be rewrapped with EditReady before import. If you have ever imported any bare AVCHD files "in place" without rewrapping, they should probably be removed from the library and reprocessed.


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Matt Wilson
Re: Transcode to ProRes 422 or ProRes 422 HQ when you captured/shot bitrate falls between the two?
on Apr 29, 2017 at 8:50:47 pm

Thanks for the tips.


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