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[whatwg] Codecs for <audio> and <video>

From: Philip Jägenstedt <philipj@opera.com>
Date: Thu, 02 Jul 2009 16:06:58 +0200
Message-ID: <op.uwf1hwsjsr6mfa@nog>
On Wed, 01 Jul 2009 19:01:02 +0200, Philip J?genstedt <philipj at opera.com>  
wrote:

> On Wed, 01 Jul 2009 18:29:17 +0200, Peter Kasting <pkasting at google.com>  
> wrote:
>
>> On Wed, Jul 1, 2009 at 2:41 AM, Anne van Kesteren <annevk at opera.com>  
>> wrote:
>>
>>> On Tue, 30 Jun 2009 21:39:05 +0200, Peter Kasting <pkasting at google.com>
>>> 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 J?genstedt
Core Developer
Opera Software
Received on Thursday, 2 July 2009 07:06:58 UTC

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