[M4IF Technotes] Compression factor to determine bit rates

[William J. Fulco]

MessageRob,
Thanks for the rant-reference :-)  I've never really known how to deal with
this "compression ratio" term (I'm sure Peter is laughing as he reads this).
What I end up doing is just saying things like (yes, II know this is VERY
SQUISHY)....
DVD-like quality at 1mbps or "about VHS quality" at 500kbps or "decent QCIF
15fps at 64kbps" - that's about all I think you can do that means ANYTHING
to anyone... You could try to do things like saying "Full NTSC at a PSNR of
38db at 1mbps" - but who knows what THAT means... we all have a subjective
experience of a VHS tape or a DVD disk or "OK quality" or "decent quality"
or "really sucky quality" and we all know what our desired-channel bit rate
is...
I mean REALLY what is someone going to do? "my codec is better than your
codec because it gets 200:1 compression ration while yours only gets 112:1-
na-na-na-na-na!!" .... the only think that matters is 1) is the output
quality either near the input quality or "good enough" for your application
and 2) what's the target bit rate... everything else is just so much
posturing ... (granted us algorithm designers do like to know things like
PSNR and such while we're beating our implementations into submission - but
"compression ratio" qua "quality measurement" is just useless.
++Bill
William J. Fulco
wjf   NetworkXXIII.com
310-927-4263 Cell
---------------------------------
Logic: When you absolutely, positively
must refute every fallacy in the room.
  -----Original Message-----
  From: technotes-admin   lists.m4if.org
[mailto:technotes-admin   lists.m4if.org]On Behalf Of Rob Koenen
  Sent: Friday, January 17, 2024 3:42 PM
  To: 'Nikki Cranley'; Technotes   lists.m4if.org
  Subject: RE: [M4IF Technotes] Compression factor to determine bit rates
  Compression factor is (bitrate in) / (bitrate out).
  See http://lists.m4if.org/pipermail/technotes/2003-January/001593.html for
  some thoughts on how useful the term is.
  Rob
    -----Original Message-----
    From: Nikki Cranley [mailto:94426082   eeng.dcu.ie]
    Sent: Friday, January 17, 2024 8:26 AM
    To: Technotes   lists.m4if.org
    Subject: [M4IF Technotes] Compression factor to determine bit rates
    Hi,
    I was wondering if someone may know of a formule that
    relates: bit rate = width x height x fps x color depth x compression
factor
    However, what Ive discovered is that the
    compression factor = fn[frame rate, resolution]
    Has anyone else come across this and got a formula for it?
    Thanx a million, rgds,
    Nikki
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