Transcoding DNX145

[Glen Montgomery]

Ya you are going to get a size increase like that with any conversion from a highly compressed format into an intermediate codec like DNxHD or ProRes. I think with 145 it is about a gig a minute. Here is Avid’s PDF on DNxHD that has a bunch of charts showing expected conversion results https://www.avid.com/static/resources/US/documents/dnxhd.pdf

Editor / Motion Graphics Artist
http://www.GlenMontgomeryIII.com

[William Holden]

Thanks!

[John Pale]

Why are you transcoding, may I ask.

I have worked on large projects with XDCAM HD and SD and found it works decently native.

[William Holden]

XDCAM is a compressed format so the supe said it wouldn’t be appropriate for the online and delivery. I suggested consolidating the XDCAM to the Unity and rendering in DNX145 (to save some transcoding time) but since they own the Unity and don’t care about how much space is used, they said they’d rather just have it in DNX145

[John Pale]

Do what you have to do, if they are forcing you but transcoding, even to a great codec like DNX is double compressing…not making the quality better. It’s still XDCAM compressed in the camera. I would definitely have your renders and imports set to DNX, though.

[Glen Montgomery]

I will agree that it will not make your already compressed footage look any better but it is not a double compression. Both the DNxHD and ProRes codecs are so good there is almost no difference between the original and transcoded clips. There are tons of reports of film editors blowing DNx-36 up on preview screens and being stunned by the quality. All this aside, the big thing is what you will do to the footage after transcoding. All your effects and color correction will be affecting a much higher quality file that you can push around with less damage then if you were pushing around the XDCAM clip, especially in the DNxHD-X 10 bit forms. It sucks to take the space and time hit making the new files but it is better to take the pain at the beginning of the project then when you have to transcode your sequence at the end. Plus getting out of the Long-GOP XDCAM keeps you out of trouble with reference files and such.

Editor / Motion Graphics Artist
http://www.GlenMontgomeryIII.com

[John Pale]

[Glen Montgomery] “but it is not a double compression”

Of course it is. Your XDCAM camera is compressing the footage while it records. When you transcode it you are compressing using the DNX codec. Its two compressions. DNX is a great codec, and will not really cause any noticable artifacts..but you will be increasing your file size quite a bit, with no benefit.

[Glen Montgomery] “ll this aside, the big thing is what you will do to the footage after transcoding. All your effects and color correction will be affecting a much higher quality file that you can push around with less damage then if you were pushing around the XDCAM clip, especially in the DNxHD-X 10 bit forms”

This is why I suggested you set your renders to DNX in the Media Creation settings. All your effects rendering will be in the DNX codec without having to transcode all your footage first.