ATI VCR1 - Revision history

Dashcloud: update link

2008-12-31T16:13:52Z

update link

← Older revision		Revision as of 09:13, 31 December 2008
Line 3:		Line 3:
	* FourCCs: VCR1		* FourCCs: VCR1
	* Company: [[ATI]]		* Company: [[ATI]]
	* Samples: [http://~~www~~.mplayerhq.hu~~/MPlayer/samples~~/V-codecs/ATI-VCR12/ http://~~www~~.mplayerhq.hu~~/MPlayer/samples~~/V-codecs/ATI-VCR12/]		* Samples: [http://samples.mplayerhq.hu/V-codecs/ATI-VCR12/ http://samples.mplayerhq.hu/V-codecs/ATI-VCR12/]

	The ATI VCR1 codec, identified by the fourcc VCR1, uses differential coding to pack Y samples. C samples are left alone. VCR1 is based on a YUV 4:1:0 colorspace. This means that each pixel in a 4x4 block has a unique Y sample while the entire block shares a C<sub>b</sub> and a C<sub>r</sub> sample.		The ATI VCR1 codec, identified by the fourcc VCR1, uses differential coding to pack Y samples. C samples are left alone. VCR1 is based on a YUV 4:1:0 colorspace. This means that each pixel in a 4x4 block has a unique Y sample while the entire block shares a C<sub>b</sub> and a C<sub>r</sub> sample.

Multimedia Mike: better wording

2008-03-10T21:49:57Z

better wording

← Older revision		Revision as of 14:49, 10 March 2008
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	* Samples: [http://www.mplayerhq.hu/MPlayer/samples/V-codecs/ATI-VCR12/ http://www.mplayerhq.hu/MPlayer/samples/V-codecs/ATI-VCR12/]		* Samples: [http://www.mplayerhq.hu/MPlayer/samples/V-codecs/ATI-VCR12/ http://www.mplayerhq.hu/MPlayer/samples/V-codecs/ATI-VCR12/]

	The ATI VCR1 codec, identified by the fourcc VCR1, uses differential coding to pack Y samples. C samples are left alone. VCR1 is based on a YUV 4:1:0 colorspace. This means that ~~for~~ each block ~~of 4x4 pixels each pixel~~ has a Y sample ~~and~~ the entire block shares ~~both~~ C ~~samples~~.		The ATI VCR1 codec, identified by the fourcc VCR1, uses differential coding to pack Y samples. C samples are left alone. VCR1 is based on a YUV 4:1:0 colorspace. This means that each pixel in a 4x4 block has a unique Y sample while the entire block shares a C<sub>b</sub> and a C<sub>r</sub> sample.

	== Data Format ==		== Data Format ==

Multimedia Mike: sample link

2006-03-16T05:56:10Z

sample link

← Older revision		Revision as of 22:56, 15 March 2006
Line 1:		Line 1:
	''This page is based on the document 'Simple YUV Coding Formats' by Mike Melanson found here: [http://multimedia.cx/simple-yuv.txt http://multimedia.cx/simple-yuv.txt].''		''This page is based on the document 'Simple YUV Coding Formats' by Mike Melanson found here: [http://multimedia.cx/simple-yuv.txt http://multimedia.cx/simple-yuv.txt].''

	* ~~FOURCCs~~: VCR1		* FourCCs: VCR1
	* Company: [[ATI]]		* Company: [[ATI]]
			* Samples: [http://www.mplayerhq.hu/MPlayer/samples/V-codecs/ATI-VCR12/ http://www.mplayerhq.hu/MPlayer/samples/V-codecs/ATI-VCR12/]

	The ATI VCR1 codec, identified by the fourcc VCR1, uses differential coding to pack Y samples. C samples are left alone. VCR1 is based on a YUV 4:1:0 colorspace. This means that for each block of 4x4 pixels each pixel has a Y sample and the entire block shares both C samples.		The ATI VCR1 codec, identified by the fourcc VCR1, uses differential coding to pack Y samples. C samples are left alone. VCR1 is based on a YUV 4:1:0 colorspace. This means that for each block of 4x4 pixels each pixel has a Y sample and the entire block shares both C samples.

Multimedia Mike at 01:35, 30 January 2006

2006-01-30T01:35:27Z

New page

''This page is based on the document 'Simple YUV Coding Formats' by Mike Melanson found here: [http://multimedia.cx/simple-yuv.txt http://multimedia.cx/simple-yuv.txt].''

* FOURCCs: VCR1
* Company: [[ATI]]

The ATI VCR1 codec, identified by the fourcc VCR1, uses differential coding to pack Y samples. C samples are left alone. VCR1 is based on a YUV 4:1:0 colorspace. This means that for each block of 4x4 pixels each pixel has a Y sample and the entire block shares both C samples.

== Data Format ==

The format of a VCR1-encoded video chunk is as follows:

bytes 0-31 16 16-bit, signed, little-endian deltas used in this frame
bytes 32.. encoded YUV data

The deltas are apparently 16 bits in width which is somewhat irrelevant since the Y samples to which they are applied are only 8-bit numbers.

The YUV data is coded after the initial deltas. The data is coded as:

luminance/chrominance line
luminance line
luminance line
luminance line
[...]

Every fourth line, starting with line 0, contains both luminance (Y) and chrominance (C) data. The other lines only contain Y data.

Each Y/C line begins with 4 offsets to be used when decoding the Y data for the next 4 lines:

byte 0 offset for this line's Y data
byte 1 offset for second line's Y data
byte 2 offset for third line's Y data
byte 3 offset for fourth line's Y data
bytes 4.. Y/C data

For the remainder of the data on a Y/C line, these 6 pieces of data:

Y0 Y1 Y2 Y3 U V

are encoded within groups of 4 bytes of the bytestream. Y0..Y3 are the next 4 Y samples in the line while U and V are the C samples for the 4 Y samples as well as the 4 Y samples on each of the next 3 lines (since this is a YUV 4:1:0 colorspace). The 4 bytes in the group have the following meaning:

byte0 byte1 byte2 byte3
Y3i Y2i V Y1i Y0i U

Bytes 1 and 3 correspond to the V and U samples, respectively. Bytes 0 and 2 break down into 4 4-bit nibbles which do not actually represent the Y samples. Instead, they index into the delta table from the start of the frame. The indexed signed delta is applied to this line's Y offset. For example,

Y0 = offset + delta_table [ byte2 & 0x0F ]
Y3 = offset + delta_table [ byte0 >> 4 ]

For the other lines that only contain Y data, each group of 4 bytes decodes to 8 Y samples in a similar manner as on the Y/C lines:

byte0 byte1 byte2 byte3
Y5i Y4i Y7i Y6i Y1i Y0i Y3i Y2i

[[Category:Video Codecs]]