I-Frame Only and Long-GOP Support

[Dan Keaton]

Dear Friends,

From day one of our Flash XDR project, we realized that I-Frame Only mode (Intra-Frame Compression) was ideal for some situations.

And Long-GOP (Inter-Frame Compression) is ideal for other situations.

So, we wanted to support both in our Flash XDR.

For a while now, we have fully supported I-Frame Only mode in the Flash XDR. This is in addition to the Long-GOP modes that we originally supported.

Now that this has been field tested in feature productions we can report the results.

Thomson Viper users have warmly received our I-Frame Only mode. A high-end action film was shooting with the Viper and Flash XDR recently. They used our I-Frame Only, 160-Mbps mode and were very pleased with the results and the workflow.

Our Long-GOP mode has also been thoroughly tested.

Many people dismiss Long-GOP. Some equate it with HDV.

Full Raster 1920 x 1080, 4:2:2 HL (high level) Long-GOP at 100 Mbps should not be dismissed lightly.

We recommend that each user perform their own tests to determine what is best for their project and their workflow.

Since the Flash XDR records Long-GOP in full raster mode, as opposed to 1440 x 1080 (for 1080 modes), the computational workload on the NLE computer is much lighter, allowing for a faster editing experience.

When a NLE has to process a 1440 x 1080 image (pixel aspect ration of 1.333), then it has to do a lot of math for every pixel. This slows down the responsiveness of the editing process, if you are working with the native files.

However, since the Flash XDR records 1920 x 1080, (pixel aspect ratio of 1.000), then this extensive math for every pixel is no longer performed.

So regardless of which HD-SDI camera you are using, you now have your choice of I-Frame Only at 100 Mbps or 160 Mbps, or Long-GOP at 50 Mbps or 100 Mbps.