Originally Posted by KenTech
Maybe someone else has the answer to this one: What IS the bit depth for the HDTV standard?
Know what you mean, Ken - some of this stuff can be difficult to dig up and "Decipher" properly ....
If I am reading some of the below correctly, I think it is 8bit(chrominance or luminance) by the time it gets to us via ATSC/MPEG2 encoding at the "source"(a broadcaster, for instance).
So, I believe this offers a fair summary, which AFAIK
is correct :
This ( http://www.hdtvprimer.com/ISSUES/what_is_ATSC.html
) says :
"For ATSC MPEG-2 the colors are represented as Y, Pr
, and Pb, which are defined as:
Y = Red+Green+Blue (Y is also called intensity or luminance and is sometimes depicted as white.)
Pb = Blue-Y (Pr
and Pb are the color information, or chrominance.)
There is only one Pr
and Pb pixel for every four Y pixels. Thus 720p has 1280*720=921,600 Y pixels plus 230,400 Pr
pixels plus 230,400 Pb pixels.........
Although the color information is at a lower resolution, human eyes can rarely sense this at the correct sitting distance ........
The Y information is encoded as an 8-bit number. Pr
and Pb likewise are 8-bit numbers. The monitor will eventually convert YPrPb into RGB. The number of bits per visible pixel averages out to 12, not 24...... "
There are some good sites online that explain how the gamut of the different technologies relate to the defined digital-TV standards.
Also, for those interested, Detailed info on ATSC standard(used for DTV/HD in U.S.) in the form of downloadable(free) PDF white papers can be found here :http://www.atsc.org/standards.html
The document labeled "A/54A "ATSC Recommended Practice: Guide to the Use of the ATSC Digital Television Standard" is probably the one I use or refer to most often - Here's a direct link to it :http://www.atsc.org/standards/a_54a.pdf
Back to "HDTV color" ... On Page 22, Section 5.2.2 of the A54 document it says :
"5.2.2 Precision of Samples
Samples are typically obtained using analog-to-digital converter circuits with 10-bit precision. After studio processing, the various luminance and chrominance samples will typically be represented using 8 or 10 bits per sample for luminance and 8 bits per sample for each chrominance component. The limit of precision of the MPEG-2 Main Profile is 8 bits per sample for each of the luminance and chrominance components."
Note on above : I wouldn't think A/D conversion would be needed for a signal that is already "digital" such as a Network HD feed.
Section 188.8.131.52 (also on page 22) also has some info that may be of some interest here concerning color and ATSC :
For the purposes of the Digital Television Standard, colorimetry means the combination ofcolor primaries, transfer characteristics, and matrix coefficients. Video inputs conforming to SMPTE 274M and SMPTE 296M have the same colorimetry; in this document, this will be referred to as SMPTE 274M colorimetry. Note that SMPTE 274M colorimetry is the same as ITU-R BT. 709 Part 2 colorimetry. Video inputs corresponding to ITU-R BT. 601-5 should have SMPTE 170M colorimetry. ISO/IEC 13818-2 allows the encoder to signal the input colorimetry parameter values to the decoder. If sequence_display_extension() is not present in the bit stream, or if color_description is zero, the color primaries, transfer characteristics, and matrix coefficients are assumed to be implicitly defined by the application. Therefore, the colorimetry should always be explicitly signaled using sequence_display_extension(). If this information is not transmitted, receiver behavior cannot be predicted.
In generating bit streams, broadcasters should understand that some receivers will display 480-line formats according to SMPTE 170M colorimetry (value 0x06) and 720- and 1080-line formats according to SMPTE 274M colorimetry (value 0x01). It is believed that few receivers will display properly the other colorimetry combinations allowed by ISO/IEC 13818-2. Legacy material using SMPTE 240M colorimetry should be treated as if it used ITU-R BT. 709 Part 2 colorimetry.
Hope some of the above is of some interest ...