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CIF and QCIF Video Formats

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anssprasad

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application of qcif and cif video formats

Can anyone give me a doc that explains clearly about the CIF and QCIF Video Formats.

Thanks
Prasad.
 

avimit

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cif samples

Hi,
QCIF and CIF is a raw collection of pixels composed of what are called luma, cb, cr
in the following array format.
A luma frame is composed of 176x144 luma samples, followed by 88x72 cb samples followed by 88x72 cr samples.
qcif frame:
unsigned char luma[176][144];
unsigned char cb[88][72];
unsigned char cr[88][72];

cif frame:
unsigned char luma[352][288];
unsigned char cb[176][144];
unsigned char cr[176][144];

Want to read these frames out of a qcif file? I have some very simple C programs which can read these values for you.
http://www.vlsiip.com/video
Kr,
Avi
 

    anssprasad

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anssprasad

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cif qcif samples

Can you give me more info regarding the CIF format. I could not find much in the books and on the net.


Thanks
Prasad.
 

avimit

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CIF is a very simple format: Its raw video.
What it contains is 'Frames'
A collection of frames is a video
Each frame in CIF is composed of the following sub frames:
luma sub frame, cb cub frame , cr sub frame.
luma sub frame in CIF is a vector of 352x288 8 bit values
cb sub frame in CIF is a vector of 176x144 8 bit values
cr sub frame in CIF is a vector of 176x144 8 bit values.
So if you declare
unsigned char luma[352][288];
unsigned char cb[176][144];
unsigned char cr[176][144];
in your c program, and read in these vectors from a CIF file,
you will have just read a 'frame' from CIF
hope it helps,
Kr,
Avi
http://www.vlsiip.com
 

mta97e

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CIF and QCIF are size of frame.

CIF and QCIF represents just the resolution(size) of the frame. I doesnt have any relation wiht Luma and chroma samples. The Luma and Cr, Cb depends on the sub sampling format.

The resolution of CIF is 352x288 in PAL and 352x240 in NTSC. The size of the QCIF is 1/4 of CIF, 176x144 in PAL and 176x120 in NTSC.

I will write a bit mroe about Lum and Chroma samples.
In the case of PAL CIF
The number of Lumer samples is 352x288. The number of Luma is always equal to teh resolution. And the number of Cr, Cb depends on the smapling format. Most popular sampling formats are 4:2:2 and 4:2:0.

If 4:4:4, number of Cr, Br and Luma is 352x288
If 4:2:2, the number of Luma is 352x288 and Cr,Cb is 176x144 (1/2)
If 4:2:0, the number of Luma is 352x288 and Cr,Cb is 88x72 (1/4)

Added after 10 minutes:

If 4:4:4, number of Cr, Br and Luma is 352x288 ... is wrong.


Sorry, 4:4:4 foramt is the RGB color space. It dose not have any chroma subsampling at all.

4:4:4 is RGB color space
 

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