HD-SDI to HDMI quality loss...?

[Mark Edwards]

Okay, my question is whenever this cineform hdmi recorder comes out will I be able to use it with an EX1 and keep the same hd-sdi quality? If I use a blackmagic-design hdlink and convert the HD-SDI to HDMI will it lose quality? Does it stay 10bit through HDMI? Will the audio go through?
Thanks alot and By the way, when Adam Wilt reviewed the EX1, did he record to SxS when measuring latitude? If he can read 10 stops from SxS 8bit, do you think that recording the hd-sdi at 10bit could give 11 stops?

[Michael H. Stevens]

Originally Posted by Mark Edwards

Okay, my question is whenever this cineform hdmi recorder comes out will I be able to use it with an EX1 and keep the same hd-sdi quality? If I use a blackmagic-design hdlink and convert the HD-SDI to HDMI will it lose quality? Does it stay 10bit through HDMI? Will the audio go through?
Thanks alot and By the way, when Adam Wilt reviewed the EX1, did he record to SxS when measuring latitude? If he can read 10 stops from SxS 8bit, do you think that recording the hd-sdi at 10bit could give 11 stops?

Being digital with no decodeing, if you use the right equipment there should be no loss. I think I am getting 11 stops with the SxS sometimes which i find more than enough for me, but you should get better color information. I don't see why you would get more latitude - just more detail within that latitude.

[Alexander Ibrahim]

The HDMI spec supports 10 bit and deeper color, so theoretically there is no loss.

Practically however you need to examine the specific implementations of the various devices.

If one of the devices in your signal chain truncates the data to 8 bit, then you will "only" gain the advantages of better chroma subsampling and lower compression. That's still pretty darn good, but it makes the overall value a bit different.

HDMI 1.3 optionally supports 30-bit, 36-bit, and 48-bit xvYCC with Deep Color, up from 24-bit sRGB or YCbCr in previous versions. (paraphrased from Wikipedia)

That means you get support for 10, 12 and 16 bit video- possibly... if your equipment supports the two latest HDMI specifications. Hence the theoretical compatibility.

Of course it also means that you have to verify that your converter supports this feature- and that the Cineform SOLID will also support it.

AJA's HI5 HD-SDI to HDMI converter is 10 bit, as noted in the AJA converter catalog- but that could be just for SDI input and internal processing. I've sent an information request to AJA support asking for more information.

Blackmagic Design's HDLINK & HDLINK PRO are based around DVI-D output, which is limited to 8-bits per pixel. They do support dual link input though- so you can get 4:4:4 8 bit HDMI.

Cineform should support 10 bit on their SDI models- they are supporting dual link after all- but I have no clue about the HDMI model. Its still in development- so its hard to say. I did ask about it, so maybe we'll see an answer here.

Convergent Designs Flash XDR also has no readily available info on bit depth so I asked. Here is the reply I got:

"We use the Sony MPEG2 4:2:2 CODEC for compressed video I/O. MPEG2, by
definition is 8-bit.

However, look for a surprise announcement regarding this issue later this
week."

[David Newman]

All CineForm compressors are now 10-bit minimum, even with 8-bit sources. So if you have a 10-bit camera, via HDMI or HDSDI, all the precision will be preserved. If an external HDSDI to HMDI preserves the bit-depth, so will the subsquent capture.

[Alexander Ibrahim]

Originally Posted by Alexander Ibrahim

AJA's HI5 HD-SDI to HDMI converter is 10 bit, as noted in the AJA converter catalog- but that could be just for SDI input and internal processing. I've sent an information request to AJA support asking for more information.

And here is the reply I got from AJA:
"The Hi-5 meets the 1.2 standard and it is an 8-bit device.
10-bit signals are dithered from 10 to 8 bits by the Hi5...this reduces
banding."

So... the AJA will concatenate the signal to a dithered 8 bits per pixel.

Also it appears to be a 4:2:2 only device.

That means that the Blackmagic HDLINKs are more suited to this type of work if you might use a 4:4:4 camera. Also the HDLINK can be had about $30 cheaper at $420 from B&H.

Otherwise the dithering in the AJA HI5 may serve you better. (B&H has the HI5 for... you guessed it $450)

Overall it will be better to wait until you can purchase the SDI version of the Cineform SOLID. Of course we haven't heard about pricing for an SDI SOLID, my guess is that it will be more than the HDMI version.

A Convergent Design's Flash XDR may be a good solution depending on their announcement later this week. I think its priced much higher though at $4995 USD.

[Christopher Ruffell]

I own Convergent Designs' nanoConnect HDMI - to HD-SDI convertor (so the reverse) and I called up to inquire recently: all the HDMI-specs currently carried by the company are 8bit.

I bet everything after the Flash XDR will be 10bit though.