Learning about the Canon XL-H1

This camera caught me by surprise as many of the camera vendors now contact CineForm before they announce their HDV camera (even many non-HDV vendors discussion CineForm implementations.) However this is a very nice surprise, and we all expect Canon to have a high quality solution. As the XL-H1 is a 1080i HDV camera it will be closely compared with the Sony HVR-Z1; neither camera offers a progressive imaging sensor, yet both have a pseudo 24 frames implementation -- speculation on this is great as the Sony method under-whelmed the market, Canon may/should take a different approach (see my speculation below). The good news is this new camera should operate flawlessly with all CineForm products as it complies with existing HDV and HDSDI (bonus) standards.

The clear difference between this unit and other HDV cameras is the addition of HDSDI. We already have several customers using live HDSDI feeds into Prospect HD workstations for onset capture, bypassing the camera compression of HDCAM/DVCPRO-HD etc, so the same work-flow will apply for the Canon XL-H1. So just like the high end HD solutions, the HDSDI feed is pre-compression, the raw data from this HDV camera is the highest quality feed, perfect for Prospect HD's 10-bit CineForm Intermediate compression (the HDV tape acts as a backup only.) There has been speculation whether the HDSDI feed is 8-bit or 10-bit YUV 4:2:2. I believe it is more likely to be 10-bit, counter to a few opinions, as there is no technical reason not to output 10-bit. The RGB CCDs capture light in a linear manner with 12 to 14 bits of precision (depending on the sensor), after in camera processing the resulting RGB linear data is converted to YUV 4:2:2 in a 709 colorspace. The RGB precision is plenty to support a 10bit YUV gamma corrected output. The top 8-bits would then be sent on to the MPEG compressor (where it is further down sampled to 4:2:0.) If the processed linear RGB data is converted directly to 8-bit YUV, that would have been an error on the part of Canon engineering (so I don't think they would have done this), particular as HDSDI is inherently 10-bit (8-bit data is sent as 10bit with the two least significant pixels set to zero.) So as soon as cameras are available it is straight forward to determine the bit-depth of the HDSDI feed.

As we will get an uncompressed 1920x1080 out from HDSDI (higher than HDV's 1440x1080) the sensor resolution is significant. Canon has increased the resolution over the Sony Z1's three CCDs of 960x1080 (which use a horizontal pixel shift of the green sensor to increase the effective resolution to approach that of 1440.) Instead the XL H1 has gone with 3 16x9 CCDs of 1.67M pixels each, suggesting a sensor resolution of around 1720x970 (assuming square pixels.) I just read that the effective sensor area for HD is 15.6M pixels, which would indicate of non-square pixel sensor of 1440x1080 (which makes better sense.) If the lens allows, this should resolve a sharper (or detailed) image. The down size of so many picture elements on a 1/3" CCD, is a reduced light sensitivity. Sony the 960x1080 CCD, with their extra elongated pixels, have a larger area to collect light, and therefore potentially slightly more sensitive.

The most anticipated element of the XL H1 will be how it achieves 24 frame acquisition using a interlaced sensor. Canon has been up front with the 24 mode not being acquired in a true progressive sense, but in one statement it seems it will not have the motion jutter of Sony's CineFrame 24, which suggests the sensor may be run at 48Hz rather then 60Hz for the 24F mode. This will be an excellent first step. However if all data is interpolated from a top or bottom field, the vertical resolution can't exceed 540. I don't give much weight to an intelligent de-interlacing process, as that will potentially introduce motion artifacts as the good algorithms would take too long for the camera to compute. Canon could generate a good resolution pseudo progressive image if they ran the green CCD with reversed field dominance (output a bottom field when red and blue CCD output a top field) this way the same pixel shifting technology that makes Sony's 960 res CCD output near 1440, could help the three 540 fields (red-blue and pixel shifted green) could achieve a progressive vertical resolution approaching 810 (which is about the maximum a normal interlace picture can achieve any way.)

One last note on the 24F mode. The "Advance" 2:3:3:2 pull-down of 24p DV is unnecessary in HDV as there in no frame compression used in the 1440x1080 mode (spec HD2.) As only field compression is used, the standard 2:3:2:3 pull-down will work perfectly well. A true progressive frame signal can be exacted with ease.

P.S. 10/12/05 -- Now that we have a camera I have posted some real world data.