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Editing Long-GOP in FCP 10.4.6
Hi,
I’m considering purchasing the Canon XC15 4K Professional Camcorder which in 1080p writes to SD cards at up to 50 Mbps in an H.264-based, Long-GOP, 4:2:2, 8-bit codec in an MXF wrapper. The sales rep at B&H told me that Long GOP could present a problem in editing causing dropped frames, jerky movement. I’m running FCP 10.4.6 on a 2011 iMac, 3.1 GHz Intel Core i5 and 20 GB RAM. I would be interested to know if anybody else has experienced any difficulty editing in this format.
Thanks,
Phil -
6 Replies
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I’ve edited some XC15 4k MXF material in FCPX and it worked very well. However I think this was “all intraframe” (not Long GOP), and the bit rate was about 300 mbps. The XC15 has several available codecs. I no longer have that material on line and unfortunately don’t have time to retrieve it from archives.
What the B&H rep told you is generally correct. It is difficult to edit smoothly 4k Long GOP (e.g, H264) on almost any Mac, including an iMac Pro.
The 2011 iMac had a “Sandy Bridge” CPU, which was the first generation of Quick Sync. That feature is vital for smoothly processing H264 material. Later Intel CPUs improved this, in particular the Kaby Lake version in the 2017 iMac was about 2x faster than the Skylake version in the 2015 iMac (as used by FCPX).
1080p is 1/4 the pixels of UHD 4k so is a lot easier to process. My gut feel is your 2011 iMac would handle this OK. It won’t be a speed demon but it will handle it. That said a 2011 iMac is getting pretty old so it would be a good idea to consider a newer machine, especially if you ever consider 4k.
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Joe,
Thanks for the input. Would transcoding to ProRes or proxy files make a difference?
Phil
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Yes that would help a lot. Optimized media is original resolution ProRes and is about 5x or 6x the file size of H264. Proxies of 4k are ProRes 422 at 1080p. Those are about 60% the file size of 4k H264.
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So, Joe, are you saying that in order to achieve smoother editing in 1080p Long-GOP, it makes sense to transcode to ProRes?
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If you are only editing a single stream of 1080p Long GOP H264, most computers and NLEs are fast enough to handle this without proxies or optimized media. This includes FCPX on a 2011 iMac.
For most 4k H264, a 2011 iMac is not fast enough except for the special case of the XC-15 using the 305 mbps “all intraframe” codec. That is technically H.264 but it’s not Long GOP, hence it’s much faster to edit. So ironically your 2011 iMac might be able to edit that specific 4k codec more smoothly than the 1080p Long GOP codec. However it takes up a lot more space — but then so do proxies or optimized media.
So youf computer is probably fast enough for 1080p Long GOP without using proxies or optimized media. It is not fast enough for regular 4k H264 (which is usually Long GOP), except if using proxies or optimized media.
For the XC15 305 mbps 4k H264 codec, that is not Long GOP so it’s possible your 2011 iMac might be fast enough to edit that without proxies or optimized media.
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Thank you again, Joe, for the valuable input. It helps me a lot.
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