Editing Serial digital interface (section)

===Color encoding===
Several color encodings are possible in the serial digital interface. The default (and most common case) is 10-bit linearly sampled video data encoded as 4:2:2 [[YCbCr]]. (YCbCr is a digital representation of the [[YPbPr]] colorspace). Samples of video are stored as described above. Data words correspond to signal levels of the respective video components, as follows:

* The luma (Y) channel is defined such that a signal level of 0&nbsp;mV is assigned the codeword 64 (40 hex), and 700 millivolts (full scale) is assigned the codeword 940 (3AC hex) .
* For the chroma channels, 0&nbsp;mV is assigned the code word 512 (200 hex), −350&nbsp;mV is assigned a code word of 64 (40 hex), and +350&nbsp;mV is assigned a code word of 960 (3C0 hex).
Note that the scaling of the luma and chroma channels is ''not'' identical. The minimum and maximum of these ranges represent the preferred signal limits, though the video payload may venture outside these ranges (providing that the reserved code words of 0–3 and 1020–1023 are ''never'' used for video payload). In addition, the corresponding analog signal may have excursions further outside of this range.

====Colorimetry====
As YPbPr (and YCbCr) are both derived from the [[RGB]] colorspace, a means of converting is required. There are three [[colorimetry|colorimetries]] typically used with digital video:
* SD and ED applications typically use a colorimetry matrix specified in [[Rec. 601|ITU-R Rec. 601]].
* Most HD, dual link, and 3&nbsp;Gbit/s applications use a different matrix, specified in [[Rec. 709|ITU-R Rec. 709]].
* The [[Multiple sub-Nyquist sampling encoding|1035-line MUSE]] HD standards specified by SMPTE 260M (primarily used in [[Japan]] and now largely considered obsolete), used a colorimetry matrix specified by SMPTE 240M. This colorimetry is nowadays rarely used, as the 1035-line formats have been superseded by 1080-line formats.

====Other color encodings====
The dual-link and 3&nbsp;Gbit/s interfaces additionally support other color encodings besides 4:2:2 YCbCr, namely:

* 4:2:2 and 4:4:4 YCbCr, with an optional ''alpha'' (used for linear keying, a.k.a. [[alpha compositing]]) or data (used for non-video payload) channel
* 4:4:4 RGB, also with an optional alpha or data channel
* 4:2:2 YCbCr, 4:4:4 YCbCr, and 4:4:4 RGB, with 12 bits of color information per sample, rather than 10. Note that the interface itself is still 10 bit; the additional 2 bits per channel are multiplexed into an additional 10-bit channel on the second link.

If an RGB encoding is used, the three primaries are all encoded in the same fashion as the Y channel; a value of 64 (40 hex) corresponds to 0&nbsp;mV, and 940 (3AC hex) corresponds to 700&nbsp;mV.

12-bit applications are scaled in a similar fashion to their 10-bit counterparts; the additional two bits are considered to be [[Least significant bit|LSBs]].