Kega Video - Revision history

Multimedia Mike: Update sample location

2010-04-01T04:32:10Z

Update sample location

← Older revision		Revision as of 21:32, 31 March 2010
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	* FourCC: KGV1		* FourCC: KGV1
	* Sample: http://samples.mplayerhq.hu/V-codecs/kgv1~~.avi~~		* Sample: http://samples.mplayerhq.hu/V-codecs/kgv1/

	Codec used for capturing videos in some Sega emulator called Kega.		Codec used for capturing videos in some Sega emulator called Kega.

DrV at 15:47, 3 February 2010

2010-02-03T15:47:31Z

← Older revision		Revision as of 08:47, 3 February 2010
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	Codec used for capturing videos in some Sega emulator called Kega.		Codec used for capturing videos in some Sega emulator called Kega.

	It produces output in ~~RGB565~~ and coding is LZ-like.		It produces output in RGB555 and coding is LZ-like.

	Frame starts with two bytes which code real dimensions as multiple of 8 minus 1 block (i.e. <code>width = (src[0] + 1) * 8;</code>, same for height), the rest is coded data.		Frame starts with two bytes which code real dimensions as multiple of 8 minus 1 block (i.e. <code>width = (src[0] + 1) * 8;</code>, same for height), the rest is coded data.
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	Coded data consists of 16-bit LSB control words with possible extensions:		Coded data consists of 16-bit LSB control words with possible extensions:

	# <code>111x xxyy yyyy yyyy</code> - copy <code>(y+3)</code> pixels from positive offset <code>offsets[x]</code> in the previous frame. If <code>offsets[x]</code> is not yet defined for this frame, read 24-bit LSB word after this code word. Naturally, this is possible only in interframes. The offset may wrap around the frame, depending on the current ~~offset~~ position.		# <code>111x xxyy yyyy yyyy</code> - copy <code>(y+3)</code> pixels from positive offset <code>offsets[x]</code> in the previous frame. If <code>offsets[x]</code> is not yet defined for this frame, read 24-bit LSB word after this code word. Naturally, this is possible only in interframes. The offset may wrap around the frame, depending on the current output position.
	# <code>110y yyyy yyyy yyyy</code> - read run length value minus four from next byte (i.e. <code>run = get_byte() + 4</code>) and copy pixels from negative offset <code>y+1</code> (e.g. offset 0 means RLE, offset 1 means repeating last two pixels, etc.)		# <code>110y yyyy yyyy yyyy</code> - read run length value minus four from next byte (i.e. <code>run = get_byte() + 4</code>) and copy pixels from negative offset <code>y+1</code> (e.g. offset 0 means RLE, offset 1 means repeating last two pixels, etc.)
	# <code>101y yyyy yyyy yyyy</code> - same as above but always copy 3 pixels from given offset		# <code>101y yyyy yyyy yyyy</code> - same as above but always copy 3 pixels from given offset

DrV at 15:39, 3 February 2010

2010-02-03T15:39:33Z

← Older revision		Revision as of 08:39, 3 February 2010
Line 10:		Line 10:
	Coded data consists of 16-bit LSB control words with possible extensions:		Coded data consists of 16-bit LSB control words with possible extensions:

	# <code>111x xxyy yyyy yyyy</code> - copy <code>(y+3)</code> pixels from positive offset <code>offsets[x]</code>. If <code>offsets[x]</code> is not yet defined for this frame, read 24-bit LSB word after this code word. Naturally, this is possible only in interframes.		# <code>111x xxyy yyyy yyyy</code> - copy <code>(y+3)</code> pixels from positive offset <code>offsets[x]</code> in the previous frame. If <code>offsets[x]</code> is not yet defined for this frame, read 24-bit LSB word after this code word. Naturally, this is possible only in interframes. The offset may wrap around the frame, depending on the current offset position.
	# <code>110y yyyy yyyy yyyy</code> - read run length value minus four from next byte (i.e. <code>run = get_byte() + 4</code>) and copy pixels from negative offset <code>y+1</code> (e.g. offset 0 means RLE, offset 1 means repeating last two pixels, etc.)		# <code>110y yyyy yyyy yyyy</code> - read run length value minus four from next byte (i.e. <code>run = get_byte() + 4</code>) and copy pixels from negative offset <code>y+1</code> (e.g. offset 0 means RLE, offset 1 means repeating last two pixels, etc.)
	# <code>101y yyyy yyyy yyyy</code> - same as above but always copy 3 pixels from given offset		# <code>101y yyyy yyyy yyyy</code> - same as above but always copy 3 pixels from given offset

Kostya: How Compn missed that?

2009-10-15T13:07:07Z

How Compn missed that?

New page

* FourCC: KGV1
* Sample: http://samples.mplayerhq.hu/V-codecs/kgv1.avi

Codec used for capturing videos in some Sega emulator called Kega.

It produces output in RGB565 and coding is LZ-like.

Frame starts with two bytes which code real dimensions as multiple of 8 minus 1 block (i.e. <code>width = (src[0] + 1) * 8;</code>, same for height), the rest is coded data.

Coded data consists of 16-bit LSB control words with possible extensions:

# <code>111x xxyy yyyy yyyy</code> - copy <code>(y+3)</code> pixels from positive offset <code>offsets[x]</code>. If <code>offsets[x]</code> is not yet defined for this frame, read 24-bit LSB word after this code word. Naturally, this is possible only in interframes.
# <code>110y yyyy yyyy yyyy</code> - read run length value minus four from next byte (i.e. <code>run = get_byte() + 4</code>) and copy pixels from negative offset <code>y+1</code> (e.g. offset 0 means RLE, offset 1 means repeating last two pixels, etc.)
# <code>101y yyyy yyyy yyyy</code> - same as above but always copy 3 pixels from given offset
# <code>100y yyyy yyyy yyyy</code> - same as above but always copy 2 pixels from given offset
# <code>0ppp pppp pppp pppp</code> - <code>p</code> is pixel value, simply output it.

Implementing decoder is left as an exercise for reader.

[[Category:Video Codecs]]