Re: Media Fragments - Video fragment temporal loop

On Fri, Feb 28, 2014 at 5:11 PM, Silvia Pfeiffer
<silviapfeiffer1@gmail.com> wrote:
>
> On 28 Feb 2014 17:46, "Philip Jägenstedt" <philipj@opera.com> wrote:
>>
>> On Fri, Feb 28, 2014 at 6:54 AM, Silvia Pfeiffer
>> <silviapfeiffer1@gmail.com> wrote:
>> > On Fri, Feb 28, 2014 at 4:16 AM, Eric Carlson <eric.carlson@apple.com>
>> > wrote:
>> >>
>> >> On Feb 27, 2014, at 8:31 AM, Philip Jägenstedt <philipj@opera.com>
>> >> wrote:
>> >>
>> >>> On Thu, Feb 27, 2014 at 10:53 PM, Raphaël Troncy
>> >>> <raphael.troncy@eurecom.fr> wrote:
>> >>>
>> >>>> What about <video>? And let's not looking at corner cases such as
>> >>>> #t=1,2.
>> >>>> People are sharing *real* fragments!
>> >>>
>> >>> The problem is the same with video, if you want to loop a particular
>> >>> scene over and over you don't want a random number of frames from the
>> >>> following scene to be shown just before the loop. This will happen if
>> >>> the looping isn't implemented inside the media framework.
>> >>>
>> >>
>> >>   For whatever it is worth, I agree with Philip - consistent and
>> >> accurate gapless looping is not possible without low level support from the
>> >> media engine.
>> >
>> > Isn't that true also for looping over full files? So doesn't that mean
>> > that the @loop attribute is useless?
>>
>> As Eric pointed out there is a difference. Without media framework
>> support looping a fragment will play beyond the loop point, while the
>> looping the entire resource will pause for a random number of
>> milliseconds at each loop. (I honestly don't know if the loop
>> attribute is useful or not, since I've never seen it used outside of
>> test cases and demos.)
>
> Surely it can't be worse than what we are doing with MSE and HLS.

I'm not sure what you mean by worse, but MSE can't do gapless looping
between arbitrary points.

> Also surely browsers will be better at keeping the delay between loops down
> compared to apps doing it in JS.

I agree that is probable. Without any support from the media framework
both would have to be polling and extrapolating currentTime, and the
browser can bypass any currentTime caching it has.

>> Will you be filing an HTML bug on the fragment end time issue? Would
>> it help inform the discussion to have use counters for when fragment
>> start and end times are applied in Blink?
>
> If you could also count how many are using JS to imitate looping (given that
> FAIK not all browsers support the loop attribute), then we would get good
> numbers of use cases.

In my ad hoc testing all current browsers support the
HTMLMediaElement.loop IDL attribute at least, which browsers lack
support?

I don't really know how one would detect and count scripted looping,
as currentTime could be set at any time for any reason.

Philip

Received on Saturday, 1 March 2014 15:55:01 UTC