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diff --git a/third_party/libwebrtc/docs/native-code/rtp-hdrext/color-space/README.md b/third_party/libwebrtc/docs/native-code/rtp-hdrext/color-space/README.md new file mode 100644 index 0000000000..3f9485681f --- /dev/null +++ b/third_party/libwebrtc/docs/native-code/rtp-hdrext/color-space/README.md @@ -0,0 +1,88 @@ +# Color Space + +The color space extension is used to communicate color space information and +optionally also metadata that is needed in order to properly render a high +dynamic range (HDR) video stream. Contact <kron@google.com> for more info. + +**Name:** "Color space" ; "RTP Header Extension for color space" + +**Formal name:** <http://www.webrtc.org/experiments/rtp-hdrext/color-space> + +**Status:** This extension is defined here to allow for experimentation. Once experience +has shown that it is useful, we intend to make a proposal based on it for standardization +in the IETF. + +## RTP header extension format + +### Data layout overview +Data layout without HDR metadata (one-byte RTP header extension) + 1-byte header + 4 bytes of data: + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | ID | L = 3 | primaries | transfer | matrix | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |range+chr.sit. | + +-+-+-+-+-+-+-+-+ + +Data layout of color space with HDR metadata (two-byte RTP header extension) + 2-byte header + 28 bytes of data: + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | ID | length=28 | primaries | transfer | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | matrix |range+chr.sit. | luminance_max | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | luminance_min | mastering_metadata.| + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |primary_r.x and .y | mastering_metadata.| + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |primary_g.x and .y | mastering_metadata.| + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |primary_b.x and .y | mastering_metadata.| + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |white.x and .y | max_content_light_level | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | max_frame_average_light_level | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +### Data layout details +The data is written in the following order, +Color space information (4 bytes): + * Color primaries value according to ITU-T H.273 Table 2. + * Transfer characteristic value according to ITU-T H.273 Table 3. + * Matrix coefficients value according to ITU-T H.273 Table 4. + * Range and chroma siting as specified at + https://www.webmproject.org/docs/container/#colour. Range (range), horizontal (horz) + and vertical (vert) siting are merged to one byte by the operation: (range << 4) + + (horz << 2) + vert. + +The extension may optionally include HDR metadata written in the following order, +Mastering metadata (20 bytes): + * Luminance max, specified in nits, where 1 nit = 1 cd/m<sup>2</sup>. + (16-bit unsigned integer) + * Luminance min, scaled by a factor of 10000 and specified in the unit 1/10000 + nits. (16-bit unsigned integer) + * CIE 1931 xy chromaticity coordinates of the primary red, scaled by a factor of 50000. + (2x 16-bit unsigned integers) + * CIE 1931 xy chromaticity coordinates of the primary green, scaled by a factor of 50000. + (2x 16-bit unsigned integers) + * CIE 1931 xy chromaticity coordinates of the primary blue, scaled by a factor of 50000. + (2x 16-bit unsigned integers) + * CIE 1931 xy chromaticity coordinates of the white point, scaled by a factor of 50000. + (2x 16-bit unsigned integers) + +Followed by max light levels (4 bytes): + * Max content light level, specified in nits. (16-bit unsigned integer) + * Max frame average light level, specified in nits. (16-bit unsigned integer) + +Note, the byte order for all integers is big endian. + +See the standard SMPTE ST 2086 for more information about these entities. + +Notes: Extension should be present only in the last packet of video frames. If attached +to other packets it should be ignored. + |