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

[Adam Holt]

On Tue, May 30, 2017 at 2:19 PM, Adam Holt <holt at laptop.org> wrote:

> 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
>

Sorry, I meant *transcoding* (for compression especially) ...as several
countries/communities are very much asking for!


> 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 (:
>


-- 
Unsung Heroes of OLPC, interviewed live @ http://unleashkids.org !
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.laptop.org/pipermail/server-devel/attachments/20170530/5a771e01/attachment-0001.html>