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Pro Tools is pretty much industry standard when it comes to audio post production, and working to video is a common practise.
However Pro Tools can be pretty choosy when it comes to the best video format to work with, and with no official recommendation from Avid (Pro Tools parent company) it is up to the user to do the guess work.
After scouring through various audio engineering forums, I came to the conclusion that the biggest reason for poor playback performance is whether your video file uses Intra-Frame coding or Inter-Frame coding.
Without going into to much detail, Inter -Frame coding uses a kind of sampling to predict what the neighbouring frames will look like.This allows Inter-Frame codecs to achieve higher compression rates without sacrificing image quality. The most popular codec that uses Inter-Frame coding is H.264, It’s file size makes it perfect for emailing about to get agency/client sign off. I would say that 80% of video files I get sent to work with use H.264.
Pro Tools cannot achieve accurate frame by frame smooth playback with ANY video that uses Inter-Frame coding.
That leaves Intra-Frame coding. These codecs are effectively lossless, this means they are good image quality but have larger file sizes.
We cannot expect clients to bring in full lossless vision into session because they are simply an impractical file size, so I have conducted a test to find the best video file conversion settings from a 30sec 1024×576 quicktime mov using the H.264 codec.
Here are the Intra-frame codec options:
All were converted at 100% image quality for test continuity.
The good news is that all formats achieved accurate frame by frame smooth playback, however, there were discrepancies with image quality. Photo Jpeg and Apple ProRes 422 managed to accomplish a good representation of the original video, but Dv pal and DVC Pro were less impressive. This might be something to do with DV codecs using non square pixels. To view the difference have a look at the video below. (Turn HD on)
Video order : Photo Jpeg – Apple Pro Res – DV Pal – DVC pro
That means we are left with Photo Jpeg or Apple ProRes. Image quality was very close but I would have to say ProRes probably just beat it by a gnat.
In terms of file size Photo Jpeg came to 253.9 mb whereas the ProRes came in at 201.4 mb.
So thats it right? Apple ProRes 422 has slightly better image quality than Photo Jpeg and a lower file size.
Well almost, whilst sharing my findings with a friend he informed me that the Photo Jpeg codec has an optimum quality setting at 92%.Re-encoded at 92% I saw no loss of image quality but a massive reduction in file size – 120.2mb!
I will be converting my videos using the Photo Jpeg codec at a 92% quality setting. It plays back smoothy in protools, looks good and the file size won’t hog your hard drive, If hard drive space isn’t an issue then go with Apple ProRes 422 for a slightly better image quality.
Thanks for reading and feel free to share your experiences with video file formats and Pro Tools in the comment section below.