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Revision 120 - (download) (annotate)
Sat Apr 13 22:22:19 2002 UTC (17 years, 4 months ago) by chl
File size: 4336 byte(s)
Text file how to use xvid_stat with explenation of parameters
EXAMPLES for usage of xvid_stat:

**********************************************************************************

EXAMPLE 1                         

$ xvid_stat < cactus.pgm

This calls xvid_stat with standard parameters for the 3 frames from the 
cactus file from examples directory.

Output should look similar to this: 

Frame     0: intra 1, enctime =   4.7 ms length=  12470 bytes dectime =   4.2 ms PSNR 39.93
Frame     1: intra 0, enctime =   6.9 ms length=   1369 bytes dectime =   1.8 ms PSNR 40.40
Frame     2: intra 0, enctime =   6.6 ms length=   3354 bytes dectime =   2.3 ms PSNR 42.03
Avg. Q6 br 0900 (0.43 bpp) size   5731 (1146 kbps / 0.54 bpp) enc:  164.7 fps, dec:  362.0 fps
PSNR P(2): 41.22 ( 40.40 , 42.03 ; 0.4698 ) I(1): 39.93 ( 39.93 , 39.93 ; 0.0000 )


The lines in detail: 
For every input frame one line is printed containing the data:

Frame            the frame number, starting with 0
intra            if the frame was encoded as I-frame (1) or P-frame (0), 
                 when B-frames are supported, they will get a value of 2 here.

enctime          time for encoding this frame, in milliseconds (1/1000th of a second)
length           length of the MPEG-4 bitstream generated from this frame (in bytes)
dectime          time for decoding 
PSNR             picture signal to noice ratio (a measurement of quality, higher is better)

then in the end, two status lines are printed, these can be used, e.g. for automatic
quality tests:

Avg.             indicated that we are now talking about average values
Q6               quality parameter that was used (so here it was quality level 6)
br 0900          bitrate mode was used with a bitrate of 900kbps the other possibility is "q"
                 instead of "br", see another example
size 5731        average size of an encoded frame
1146 kbps        "real" bitrate that was achieved, it may differ from the bitrate given to the
                 codec as a parameter, because this is real life
0.54 bpp         number of bit per pixel for the encoding, useful when comparing videos of 
                 different size 
enc: 164.7 fps   speed of encoding in frames per second
dec: 362.0 fps   speed of decoding in frames per second

******************************************************************************************

EXAMPLE 2 

$ xvid_stat 0 0 6 900 25  < cactus.pgm 

This does exactly the same as above, but parameters   
quality = 6, 
bitrate = 900 
framerate = 25 
are provided instead of using default value. Output should be the same as in last example.
Note that first and second parameter are 0, indicating that a PGM file should be read
(which has a header that includes X and Y dimensions).

******************************************************************************************

$ xvid_stat 0 0 1 8  < cactus.pgm 

Output: 

Frame     0: intra 1, enctime =   4.1 ms length=   8420 bytes dectime =   3.4 ms PSNR 36.36
Frame     1: intra 0, enctime =   3.0 ms length=    659 bytes dectime =   1.5 ms PSNR 36.36
Frame     2: intra 0, enctime =   2.7 ms length=    595 bytes dectime =   1.5 ms PSNR 36.43
Avg. Q1  q 0008 (0.00 bpp) size   3224 ( 644 kbps / 0.31 bpp)enc:  304.3 fps, dec:  467.1 fps
PSNR P(2): 36.40 ( 36.36 , 36.43 ; 0.0210 ) I(1): 36.36 ( 36.36 , 36.36 ; 0.0000 )

This time, quality 1 is used, so output values are a little different. Since the fourth parameter
(here 8) is smaller than 32, it is not considered as a bitrate value, but as a fixed quantizer. 
So in the "Avg." line there is a 

q 0008   meaning "fixed quantizer mode" with quantizer 8. 


******************************************************************************************

$ xvid_stat 176 144 5 112  < foreman.qcif  

This switches xvid_stat to RAW instead of PGM mode. The input is expected to be 
images of dimensions 176*144 in raw YUV 4:2:0 format. (So every image is exactly
38016 = 176*144 + 88*72 + 88*72  bytes in size). Some reference streams are in
this format. Note that you MUST give correct dimensions, because they cannot be
detected from the YUV material.  
Apart from this, the example uses quality 5 and a bitrate of 112 kbps with video speed 
of 30 frames per second (this is not encoding or decoding speed, but the speed at 
which the video would be played. This value is only important for ratecontrol...) 



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