What is the data rate of the uncompressed 8-bit 422 HDMI signal on the A7S II?

[jakehuddleston]

Hello all,

 

I am looking for information about the HDMI output on the A7S II that I can't seem to find anywhere else. Essentially, what is the data rate of the uncompressed HDMI signal from the sensor, and does it vary between resolution and frame rates?

 

The A7S II is capable of outputting an uncompressed 8-bit 422 signal via its HDMI port. So many people get so caught up in the color bit depth advantage here, but very few talk about the increased data rate/bitrate that is available. This data rate increase is especially important for me due to the high-detailed, moving images I tend to shoot (a lot of nature footage on a gimbal stabilizer where the entire frame is in focus). High detail, high contrast imagery that moves through a frame tends to get heavily compressed internally by low bitrate codecs, essentially throwing away information in moving parts of the image and hoping you won't notice. (There's a great article by Art Adams at Provideo Coalition about codecs and compression that explains this in greater detail here: https://www.provideocoalition.com/here-are-my-rules-of-thumb-when-choosing-a-codec/)

 

As a rule of thumb, a higher data rate/bitrate equals sharper, better quality footage with reduced blocky artifacts because less compression is being applied and there is a greater amount of data stored within the codec. There is more to this than just data rates (such as the complicated codec algorithms), but we won't go into that here.

 

Essentially, I'm just looking for the data rate of the uncompressed HDMI signal available from the A7S Mk. II, so that I can properly choose an external recorder with the capabilities needed to record this signal at the highest possible quality.

 

If anyone can provide this information, and/or point to where you found the information, that would be extremely helpful! Thanks!