[Server-devel] KA Lite videos compress to ~41% of their original size (by Reno McKenzie)

Adam Holt holt at laptop.org
Tue May 30 14:19:46 EDT 2017


Can folks plz evaluate the quality of those videos on the left, compared to
the originals on the right?  Note that he/we did not compress the audio
channel, which should remain in very high quality stereo for now.  We've
begun by translating KA Lite's 8732 English videos, most all of which (I
believe!) originate from Khan Academy itself -- making tight compression
attractive in several communities that use SD Cards rather than hard disk
drives for their digital libraries (despite the tradeoffs you will see
below!)

Constructive criticism would be really great, as this is progressing fast,
and QA is *always* the hardest part.  e.g. What specific flaws do you see
in any video on the LEFT, that are simply unacceptable??  Some lossiness
(degradation) cannot be avoided of course!  Still, teacher's "fieldback"
would be especially interesting here (even as new many usage patterns are
evolving on small/mobile screens, outside of schools especially!!) as I
noticed widely varying compression rate across the board, across the 1st 10
videos compressed he compressed here:

   1. 5HMMfiyszjo.mp4 <http://unleashkids.org/%7Eholt/10new/5HMMfiyszjo.mp4>
   is 38.7% of 6.9M 5HMMfiyszjo.mp4
   <http://unleashkids.org/%7Eholt/10old/5HMMfiyszjo.mp4>
   2. 91wF7Ef_k8Y.mp4 <http://unleashkids.org/%7Eholt/10new/91wF7Ef_k8Y.mp4>
   is 26.6% of 17M 91wF7Ef_k8Y.mp4
   <http://unleashkids.org/%7Eholt/10old/91wF7Ef_k8Y.mp4>
   3. DNoDJlB0ygU.mp4 <http://unleashkids.org/%7Eholt/10new/DNoDJlB0ygU.mp4>
   is 54.2% of 2.8M DNoDJlB0ygU.mp4
   <http://unleashkids.org/%7Eholt/10old/DNoDJlB0ygU.mp4>
   4. KNklNvGof8o.mp4 <http://unleashkids.org/%7Eholt/10new/KNklNvGof8o.mp4>
   is 29.0% of 15M KNklNvGof8o.mp4
   <http://unleashkids.org/%7Eholt/10old/KNklNvGof8o.mp4>
   5. LDyMYyiAsQs.mp4 <http://unleashkids.org/%7Eholt/10new/LDyMYyiAsQs.mp4> is
   93.8% of 8.4M LDyMYyiAsQs.mp4
   <http://unleashkids.org/%7Eholt/10old/LDyMYyiAsQs.mp4>
   6. bcCLKACsYJ0.mp4 <http://unleashkids.org/%7Eholt/10new/bcCLKACsYJ0.mp4>
   is 49.5% of 6.1M bcCLKACsYJ0.mp4
   <http://unleashkids.org/%7Eholt/10old/bcCLKACsYJ0.mp4>
   7. do8WhQaAyso.mp4 <http://unleashkids.org/%7Eholt/10new/do8WhQaAyso.mp4>
   is is 33.5% of 25M do8WhQaAyso.mp4
   <http://unleashkids.org/%7Eholt/10old/do8WhQaAyso.mp4>
   8. iPROoc_o0p8.mp4 <http://unleashkids.org/%7Eholt/10new/iPROoc_o0p8.mp4>
   is 32.7% of 10M iPROoc_o0p8.mp4
   <http://unleashkids.org/%7Eholt/10old/iPROoc_o0p8.mp4>
   9. kkrF9X6Fycg.mp4 <http://unleashkids.org/%7Eholt/10new/kkrF9X6Fycg.mp4>
   is 40.0% of 3.5M kkrF9X6Fycg.mp4
   <http://unleashkids.org/%7Eholt/10old/kkrF9X6Fycg.mp4>
   10. meibWcbGqt4.mp4
   <http://unleashkids.org/%7Eholt/10new/meibWcbGqt4.mp4> is 55.2% of 13M
   meibWcbGqt4.mp4 <http://unleashkids.org/%7Eholt/10old/meibWcbGqt4.mp4>

AVG: compressed file is 41.0% of ORIGINAL, suggesting the 236GB of English
total may end up around 97GB, perfect (if the quality suffices!)

Thanks All !!

Challenge: if you do have a chance to express your feedback after viewing
several of the videos (new ones, on the LEFT) please also try your device
in landscape mode vs. portrait mode ...to see if that makes any difference
to the perceived quality/experience of the vid?!


PS long-term we're aware a further transcoding to WebM and/or OGV is also
necessary for compatibility on XO laptops and truly free OS's everywhere,
as such Emmanuel Engelhart (founder of Kiwix.org) may in fact be assisting
us+all here in coming months (:
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