Metadata gotcha with Avid MC at DVinfo.net

John Mitchell · February 22nd, 2010, 08:05 PM

Just a quick one - recently did a shoot using 100 Mb/s Iframe codec rather than Long GOP in order to facilitate QT ref export from Avid.

Unfortunately this didn't work as the clip is labelled in metadata XDCam HD 50Mb/s - Avid treats all XDCam HD media as LongGOP media. Trying to work out if there is any other way you could label the metadata to get this to work or if it is just a limitation of the system.

Would probably work a lot better if Avid treated the CD material as a unique codec rather than the current situation of deliberately mislabelling clips to get them to work. Do we know if that is something Avid and CD are working on?

regards John

Dan Keaton · February 22nd, 2010, 08:24 PM

Dear John,

We call our two modes as Long-GOP, and I-Frame Only.

Long-GOP normally consists of I, B and P frames. The I Frame uses Intraframe coding, and the B and P frames use data from other frames. The I-Frame stands alone.

Our I-Frame Only is properly named. It consists of only I-Frames, thus it is an Intraframe codec.

But, it is a XDCAM codec, as it is Long-GOP, but modified to just include the I-Frames, there are no B and P Frames. Again, all I-Frames in a Long-GOP structure.

Thus Avid sees it a Long-GOP, which it is technically, but it only includes I-Frames, so it is all Intraframe coding.

(Please forgive me if all of this is already obvious to you. I am thinking that it is.)

As far as I know, neither our company nor Avid are working on the issue you raise.

John Mitchell · February 22nd, 2010, 08:51 PM

Dan - do you ever sleep? Jeez fast response.

From what I understand you are probably correct - Quicktime will always treat even an I frame only codec as LongGOP and will refuse to frameserve it so I will go back to my previous workflow of LongGOP and transcoding everything to DnxHD120 on import.

Cheers John

February 22nd, 2010, 08:05 PM	#1
John Mitchell Contributor Join Date: Jul 2005 Location: Sydney Australia Posts: 873	Metadata gotcha with Avid MC Just a quick one - recently did a shoot using 100 Mb/s Iframe codec rather than Long GOP in order to facilitate QT ref export from Avid. Unfortunately this didn't work as the clip is labelled in metadata XDCam HD 50Mb/s - Avid treats all XDCam HD media as LongGOP media. Trying to work out if there is any other way you could label the metadata to get this to work or if it is just a limitation of the system. Would probably work a lot better if Avid treated the CD material as a unique codec rather than the current situation of deliberately mislabelling clips to get them to work. Do we know if that is something Avid and CD are working on? regards John

February 22nd, 2010, 08:24 PM	#2
Dan Keaton Inner Circle Join Date: Dec 2002 Location: Augusta Georgia Posts: 5,421	Dear John, We call our two modes as Long-GOP, and I-Frame Only. Long-GOP normally consists of I, B and P frames. The I Frame uses Intraframe coding, and the B and P frames use data from other frames. The I-Frame stands alone. Our I-Frame Only is properly named. It consists of only I-Frames, thus it is an Intraframe codec. But, it is a XDCAM codec, as it is Long-GOP, but modified to just include the I-Frames, there are no B and P Frames. Again, all I-Frames in a Long-GOP structure. Thus Avid sees it a Long-GOP, which it is technically, but it only includes I-Frames, so it is all Intraframe coding. (Please forgive me if all of this is already obvious to you. I am thinking that it is.) As far as I know, neither our company nor Avid are working on the issue you raise. __________________ Dan Keaton Augusta Georgia

February 22nd, 2010, 08:51 PM	#3
John Mitchell Contributor Join Date: Jul 2005 Location: Sydney Australia Posts: 873	Dan - do you ever sleep? Jeez fast response. From what I understand you are probably correct - Quicktime will always treat even an I frame only codec as LongGOP and will refuse to frameserve it so I will go back to my previous workflow of LongGOP and transcoding everything to DnxHD120 on import. Cheers John