MultimediaWiki - User contributions [en]

OGM

2006-09-17T20:46:02Z

Jhartmann:

Ogg Media Stream is an imcompatible hack of the [[Ogg]] media container.

Category:YCbCr Formats

2006-09-17T15:01:07Z

Jhartmann:

Various variants of color encodings based on the color space YCbCr which is used in nearly all digital video formats. (YCbCr is often falsely mixed up with the color space YUV which is only used in analog TV and video, namely in [[PAL]]-based applications.)

YUV4MPEG2

2006-09-17T14:56:59Z

Jhartmann:

* Extension: .y4m
* Samples: http://samples.mplayerhq.hu/yuv4mpeg2/

YUV4MPEG2 is a simple file format designed to hold uncompressed frames of [[YCbCr]] video formatted as [[YCbCr 4:2:0]] data for the purpose of encoding, likely to [[MPEG]]-2. The part "YUV" in its name just derives from the fact that the color space YCbCr (used for color encoding in digital media) is often falsely mixed up with the color space YUV (used in analog PAL based applications, including analog TV and video tapes).

== Data Format ==
A Y4M file begins with a plaintext, quasi-freeform header. The first 9 bytes comprise a file signature of 'YUV4MPEG2' followed by a space (ASCII 0x20). Following the signature is any number of parameters separated by a space (ASCII 0x20). The parameters that should definitely be present are width, height, and frame rate:
* frame width: 'W' followed by a plaintext integer; example: 'W720'
* frame height: 'H' followed by a plaintext integer; example: 'H480'
* frame rate: 'F' followed by the number of frames per second, a colon, and a 1 (''need more information on this one --[[User:Multimedia Mike|Multimedia Mike]]''); example: 'F30:1'
Other parameters include:
* interlacing: 'I' followed by a p to denote progressive scan (''what indicates interlaced? 'i'? Are there any other modes? --[[User:Multimedia Mike|Multimedia Mike]]''); example: 'Ip'
* Parameter 'A': Unknown; perhaps aspect ratio? example: 'A0:0'

Following the header is any number of frames coded in YCbCr 4:2:0 format in Y-Cb-Cr plane order. Each frame begins with the 5 bytes 'FRAME' followed by a sixth byte of 0x0A. The length of each frame can be computed as:

frame length = width * height * 3 / 2

[[Category:Container Formats]]

YUV 4:2:2

2006-09-17T13:49:19Z

Jhartmann: YUV 4:2:2 moved to YCbCr 4:2:2: YUV is used in analog PAL, not in digital media.

#REDIRECT [[YCbCr 4:2:2]]

YCbCr 4:2:2

2006-09-17T13:49:19Z

Jhartmann: YUV 4:2:2 moved to YCbCr 4:2:2: YUV is used in analog PAL, not in digital media.

* FourCCs: YUY2, UYVY
(These FourCC names only reflect that the YCbCr of digital media is often falsely mixed up with analog PAL's YUV color space.)

YCbCr 4:2:2 is a packed [[YCbCr]] format in which a pair of consecutive pixels is represented by 1 Y sample each but share a Cb sample and a Cr sample.

This type of data may be packaged in a container format with a a FourCC of YUY2 which indicates the following byte formatting:

Y0 Cb Y1 Cr

The first pixel is a a function of (Y0, Cb, Cr) and the second pixel is a function of (Y1, Cb, Cr). Alternately, the FourCC UYVY is used to indicate YCbCr 4:2:2 data with a byteswapped order:

Cb Y0 Cr Y1

For trivia, the 2 in YUY2 most likely refers to the number of bytes needed to represent a single pixel. Since 4 bytes represent 2 pixels, an average of 2 bytes are required to represent a single pixel in this scheme.

[[Category:YCbCr Formats]]

YCbCr 4:2:2

2006-09-17T13:48:51Z

Jhartmann:

YUV 4:2:0

2006-09-17T13:46:43Z

Jhartmann: YUV 4:2:0 moved to YCbCr 4:2:0: YUV is alalog PAL, not digital media.

#REDIRECT [[YCbCr 4:2:0]]

YCbCr 4:2:0

2006-09-17T13:46:43Z

Jhartmann: YUV 4:2:0 moved to YCbCr 4:2:0: YUV is alalog PAL, not digital media.

* FourCCs: I420, YV12
(These FourCC names only reflect that YCbCr is often falsely mixed up with analog PAL's YUV color space.)

YCbCr 4:2:0 indicates a planar [[YCbCr]] colorspace where a 2x2 block of pixels in an image is represented by 4 Y samples, 1 for each pixel, but all 4 pixels share a Cb sample and a Cr sample.

YCbCr 4:2:0 can be transported within a general purpose container format. When the data is designated with a FourCC of I420 all of the Y data appears first, followed by the Cb data, then then Cr data. YV12 is the same with the order of the Cb and Cr planes revered.

For trivia, the 12 in YV12 most likely refers to the number of bits needed to represent a single pixel. Since 6 bytes, or 48 bits represent 4 pixels, an average of 12 bits are required to represent a single pixel in this scheme.

[[Category:YCbCr Formats]]

YCbCr 4:2:0

2006-09-17T13:46:19Z

Jhartmann:

YUV 4:1:1

2006-09-17T13:44:08Z

Jhartmann: YUV 4:1:1 moved to YCbCr 4:1:1: YUV is analog PAL, not digital video.

#REDIRECT [[YCbCr 4:1:1]]

YCbCr 4:1:1

2006-09-17T13:44:08Z

Jhartmann: YUV 4:1:1 moved to YCbCr 4:1:1: YUV is analog PAL, not digital video.

YCbCr 4:1:1 refers to a packed [[YCbCr]] format in which 4 pixels in a group of 4 consecutive pixels in a row is represented by one Y sample for each pixel but all 4 pixels share a single Cb sample and a single Cr sample.

(Note that YCbCr is often falsely mixed up with analog PAL's YUV.)

[[Category:YCbCr Formats]]

YCbCr 4:1:1

2006-09-17T13:43:44Z

Jhartmann:

YUV 4:1:0

2006-09-17T13:42:48Z

Jhartmann: YUV 4:1:0 moved to YCbCr 4:1:0: YUV is nalaog PAL, not digital video.

#REDIRECT [[YCbCr 4:1:0]]

YCbCr 4:1:0

2006-09-17T13:42:48Z

Jhartmann: YUV 4:1:0 moved to YCbCr 4:1:0: YUV is nalaog PAL, not digital video.

* FourCCs: YUV9, YVU9, IFO9
* Samples: http://samples.mplayerhq.hu/V-codecs/YVU9/

''Note that thes FourCCs and other "YUV" names only reflect that YCbCr is often falsely mixed up with YUV, which is not YCbCr but a different color space that is used in analog PAL-based stuff (analog TV, video tapes, ...) and not in digital media.''

YCbCr 4:1:0 indicates a planar [[YCbCr]] colorspace where a 4x4 block of pixels in an image is represented by 16 Y samples, 1 for each pixel, but all 16 pixels share a Cb sample and a Cr sample.

If YCbCr 4:1:0 data is stored in YUV9 or IFO9 format, it is stored with all of its Y data first, then its Cb data, then its Cr data. YVU9 data swaps the Cr and Cr planes.

For trivia, the 9 in YUV9/YVU9 most likely refers to the number of bits needed to represent a single pixel. Since 18 bytes, or 144 bits represent 16 pixels, an average of 9 bits are required to represent a single pixel in this scheme.

[[Category:YCbCr Formats]]

YCbCr 4:1:0

2006-09-17T13:42:18Z

Jhartmann:

YUV 2:1:1

2006-09-17T13:38:31Z

Jhartmann: YUV 2:1:1 moved to YCbCr 2:1:1: YUV is analog PAL, not digital video.

#REDIRECT [[YCbCr 2:1:1]]

YCbCr 2:1:1

2006-09-17T13:38:31Z

Jhartmann: YUV 2:1:1 moved to YCbCr 2:1:1: YUV is analog PAL, not digital video.

YCbCr 2:1:1 refers to a packed [[YCbCr]] format in which 2 pixels in a group of 2 consecutive pixels in a row is represented by one Y sample for each pixel but both pixels share a single Cb sample and a single Cr sample.

(Note that digital YCbCr is often falsely mixed up with analog PAL's YUV.)

[[Category:YCbCr Formats]]

YCbCr 2:1:1

2006-09-17T13:38:05Z

Jhartmann:

YCbCr 2:1:1

2006-09-17T13:37:19Z

Jhartmann:

YUV 1:1:1

2006-09-17T13:36:31Z

Jhartmann: YUV 1:1:1 moved to YCbCr 1:1:1: YUV is analog PAL, not digital video.

#REDIRECT [[YCbCr 1:1:1]]

YCbCr 1:1:1

2006-09-17T13:36:31Z

Jhartmann: YUV 1:1:1 moved to YCbCr 1:1:1: YUV is analog PAL, not digital video.

YCbCr 1:1:1 refers to a packed [[YCbCr]] format in which each pixel is represented by one Y , one Cb and one Cr sample.

(Note that digital YCbCr is often falsely mixed up with analog PAL's YUV.)

[[Category:YCbCr Formats]]

YCbCr 1:1:1

2006-09-17T13:35:55Z

Jhartmann:

YCbCr

2006-09-17T13:32:05Z

Jhartmann:

Many modern video codecs rely on a YCbCr colorspace. More correctly written this is YCbCr, with the 'b' and 'r' characters as subscripts. This is what the components represent:

* Y = luminance, or intensity
* Cb = "blue chrominance", or more precise the color deviation from grey on a blue-yellow axe
* Cr = "red chrominance", or more precise the color deviation from grey on a red-cyan axe

Green can be calculated based on thes three values.

YCbCr is often falsely mixed up with YUV, which is a different colorspace that is not used in digigal media but in analog PAL-based stuff as analog TV transmission or analog video tapes.

Note that with most digital [[RGB]] color encodings, every single pixel has a different R, G, and B sample. The same is not true with many YCbCr color endodings. These YCbCr variants operate on the empirical evidence that the human eye is more sensitive to variations in the intensity of a pixel rather than variations in color. Thus, every pixel in an image of such a YCbCr variant has an associated Y sample, but groups of pixels share Cb and Cr samples.

For information on specific YCbCr formats, see the [[:Category:YCbCr Formats|YCbCr formats category page]].

[[Category:Compression Theory]]

YUV

2006-09-17T13:17:02Z

Jhartmann: YUV moved to YCbCr: common digital video is always YCbCr; YUV is a different codec, which is uses in analog PAL, not in digital video

#REDIRECT [[YCbCr]]

YCbCr

2006-09-17T13:17:02Z

Jhartmann: YUV moved to YCbCr: common digital video is always YCbCr; YUV is a different codec, which is uses in analog PAL, not in digital video

Many modern video codecs rely on a YUV colorspace. 'YUV' is a frustrating acronym since it is so difficult to guess what the letters could possibly stand for. The colorspace was originally known as YCbCr, with the 'b' and 'r' characters written as subscripts. This is what the components represent:

* Y = luminance, or intensity
* U = Cb = blue chrominance value
* V = Cr = red chrominance value

Where is green represented? Green can be derived from the Y, U, and V values.

Note that with most [[RGB]] colorspaces, every single pixel has a different R, G, and B sample. The same is not true with YUV colorspaces. YUV operates on the empirical evidence that the human eye is more sensitive to variations in the intensity of a pixel rather than variations in color. Thus, every pixel in a YUV image has an associated Y sample, but groups of pixels share U and V samples.

For information on specific YUV formats, see the [[:Category:YUV Formats|YUV formats category page]].

[[Category:Compression Theory]]