video bitrate calculation

[nivek_nayr]

hey guys, any one who knows how to calculate the video bitrate of a video?
and what bitrate of a video taken from a digicam? like sony dsc's the vids look clear,and vivid images,

[JohnnyMalaria]

Assuming the videos are files somewhere:

bitrate (Mbps) = 8 x file size (in MB) / duration (in seconds)

[nivek_nayr]

why 8 is given?
example 55.5 mb file size, duration is 39 sec
so what actually the bitrate?

[Baldrick]

Because 1 byte = 8 bits.

8 x 55.5MB / 39 secs = 11.38Mbps total bitrate (video and audio)

[nivek_nayr]

tnx for quick reply
more power to this forum..

[jagabo]

DV from a digicam will always be 25 Mb/s

[nivek_nayr]

so thats why digicam vids eats a lot of memory?

[JohnnyMalaria]

Yup, 1 hour = 13GB! And it's why DV is such high quality.

HDV cams use exactly the same bitrate but use a much more aggressive compression scheme (MPEG2).

[nivek_nayr]

how about the video bitrate of sony digital cameras like sony t9,t10,t100
these camera produce sharper and clorful videos,near dvd quality.

[edDV]

From: http://www.imaging-resource.com/PRODS/T7/T7A.HTM

"In Movie exposure mode, the camera captures either 640 x 480-, or 160 x 112-pixel resolution moving images with sound for as long as the memory card has available storage space. At the 640 x 480 setting, you can choose between Standard and Fine quality options. Standard records at 16 frames per second, while Fine records at 30 frames per second and requires Memory Stick PRO Duo media to support the necessary data rates."

Record a minute of video at 30fps and use the formula above to calculate bit rate from the file size recorded.

[nivek_nayr]

tnx a lot

[jagabo]

Bitrates of different codecs don't compare directly though.