On Wed, 01 Jul 2009 19:01:02 +0200, Philip Jägenstedt <[email protected]>
wrote:
On Wed, 01 Jul 2009 18:29:17 +0200, Peter Kasting <[email protected]>
wrote:
On Wed, Jul 1, 2009 at 2:41 AM, Anne van Kesteren <[email protected]>
wrote:
On Tue, 30 Jun 2009 21:39:05 +0200, Peter Kasting <[email protected]>
wrote:
There is no other reason to put a codec in the spec -- the primary
reason
to spec a behavior (to document vendor consensus) does not apply.
"Some
vendors agreed, and some objected violently" is not "consensus".
The "vendor consensus" line of argument seems like a very dangerous
slippery slope. It would mean that whenever a vendor refuses to
implement
something it has to be taken out of the specification. I.e. giving a
single
vendor veto power over the documentation of the Web Platform. Not good
at
all in my opinion.
I am merely echoing Hixie; from his original email in this thread:
> At the end of the day, the browser vendors have a very effective
> absolute veto on anything in the browser specs,
You mean they have the power to derail a spec?
They have the power to not implement the spec, turning the spec from a
useful description of implementations into a work of fiction.
That's something I would have considered before the advent of Mozilla
Firefox.
Mozilla also has the power of veto here. For example, if we required
that
the browsers implement H.264, and Mozilla did not, then the spec would
be
just as equally fictional as it would be if today we required Theora.
My sole goal was to try and point out that the situation with codecs is
not
equivalent to past cases where vendors merely _hadn't implemented_ part
of
the spec; in this case vendors have _actively refused_ to implement
support
for various codecs (Apple with Theora and Mozilla(/Opera?) with H.264).
PK
That is correct, we consider H.264 to be incompatible with the open web
platform due to its patent licensing. For the time being we will support
Ogg Vorbis/Theora, which is the best option patent-wise and neck-in-neck
with the competition in the quality-per-bit section (especially with
recent encoder improvements). We would love to see it as the baseline
for HTML5, but in the absense of that hope that the web community will
push it hard enough so that it becomes the de-facto standard.
A private email has correctly pointed out that "neck-in-neck" is
exaggerating Theora's quality when compared to a state of the art H.264
encoder. It's worth pointing out though that in the immediate future
Theora/Vorbis will also be competing against FLV (H.263/MP3), where it
compares favorably (especially for audio).
Some relevant reading:
http://web.mit.edu/xiphmont/Public/theora/demo7.html
http://people.xiph.org/~greg/video/ytcompare/comparison.html
http://www-cs-faculty.stanford.edu/~nick/theora-soccer/
Previously, I have watched the video's from Greg's ~499kbit/sec comparison
of H.264 (as encoded by YouTube) and Theora and it is clear that Theora
has more block artifacts and noise overall. However, in the H.264 version
when the bunny hole is zoomed in the bunny "flicks" with a period with
about 1 sec, similar to the effect of a keyframe in a dark scene (I
haven't inspected if these were actually keyframes). I'd argue that for
this clip, which you prefer depends on how you like your artifacts and if
you're watching in fullscreen or not (block artifacts are more noticeable
when magnified while a "keyframe flick" is noticeable also at 1:1
magnification). However, this comparison was only made to counter a claim
by Chris DiBona and doesn't show that Theora is "neck-in-neck" with H.264
in the general case. It does however show that it is neck-in-neck with
what YouTube produces.
I haven't watched the video's of the soccer comparison, but assume that
the conclusions are roughly correct.
H.264 is a more modern codec than Theora and will outperform it if the
best encoders from both sides are used, I don't want to imply anything
else. Still, Theora is certainly good enough at this point that the
deciding factor is no longer about technical quality, but about finding a
common baseline that everyone can support.
--
Philip Jägenstedt
Core Developer
Opera Software
