Working with HD Video

ALEXA cameras deliver an uncompressed HD video signal over a 1.5G or 3G HD-SDI connection, which makes it compatible with a large range of recording systems. It is highly recommended to involve a postproduction supervisor when selecting a recording system, as the recording format has a great impact on the overall workflow.

The few tape-based HD recording formats that are still used have been around for so long that it is easy to get a hold of a playback unit if it is not available for ingest at the post site. Most of the file-based recorders provide an easy access to recorded material through standard IT interfaces that will allow to either connect to the media directly or through a docking station.

ALEXA HD-SDI Output Formats

FORMAT BIT DEPTH COLOR SPACE STANDARD
FRAME RATES*
APPLICATION
1080p/PsF 422 1.5G SL 10 YCbCr 23.974, 24, 25, 29.97, 30 TV application.
1080p 422 1.5G DL 10 YCbCr 48, 50, 59.94, 60 Same as above at higher frame rates.
1080p/PsF 444 1.5G DL 10 RGB 23.974, 24, 25, 29.97, 30 High quality TV or cinema applications with color correction and/or visual effects.
1080p/PsF 444 3G SL 10 RGB 23.974, 24, 25, 29.97, 30 High quality TV or cinema applications with color correction and/or visual effects.
1080p 444 3G DL 10 RGB 48, 50, 59.94, 60 Same as above at higher frame rates.

*48 fps is not a standardized HD frame rate and may only be available on certain HD recorders. ALEXA also supports the output of non-standard frame rates via the Variframe flag. This feature is not available on all HD recorders.

If the original recording media needs to be re-used throughout the shoot, necessary precautions need to be taken to verify that the recorded material was transferred without any defect or degradation. If the recording is file based, the file copy should at least be confirmed using checksum verification. If the material is transferred as video signals, the copy should be checked visually, using a suitable display with native HD resolution.