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From Jeremy Quinn <>
Subject Re: Finished Video Processing
Date Sun, 19 Oct 2003 11:52:52 GMT
Sorry, this email took 4 days to arrive, my feckwit of an ISP appears 
to lurch from one email disaster to the next.

On Thursday, October 16, 2003, at 02:06 PM, Stefano Mazzocchi wrote:

> On Thursday, Oct 16, 2003, at 13:17 Europe/Rome, Jeremy Quinn wrote:
>> On Thursday, October 16, 2003, at 11:05 AM, Stefano Mazzocchi wrote:
>> <snip/>
>>>> It works beautifully when the .avi is a local file, but not when it 
>>>> is loaded over the net. I checked this in QT Player (entering the 
>>>> URL) and directly in Safari, and it also completely fails to play, 
>>>> even after having buffered it. No Audio, jerky video. I also tried 
>>>> saving the SMIL as a Composite, fast-start .mov (with external 
>>>> references), but still no go ....
>>> crap, can you post the above (and the images) somewhere on the net 
>>> so that I can see it?
>> <>
>> Keep in mind ... this is a very rough demo :)
>> ie. I did not have Steven's slides, so I blew up snapshots from the 
>> video itself.
>> I made the slide region so much bigger than the movie region so you 
>> can actually read the text on the dense ones ....
> I don't get audio,

Me neither

> but apart from that it's not too bad.

I have lots of ideas for improving it, but it hardly seems worth it if 
we cannot get the video working ....

I ought to have a go at separating the audio and video tracks (where to 
store them?). So users can choose, which they want to receive.

> Are you sure you don't have to specify the audio stream separately?

Yes, I am sure that you do not.
The .avi file contains both the audio and video tracks.

> (in fact, if you have different video streams, you need to tell which 
> one is to be heard... or, how to mix them... Andrew knows a lot about 
> SMIL, any suggestion there?)

If you load two movies with audio, they both play :)
People use this to make music mixing toys .... etc.
(OK, so this is not SMIL, but on the NĂ˜1SE home page 
<> there are two QT sound tracks, 
each a single, very close tone with a slight bend on them. Play each 
individually and it sound like a single tone, play them together and 
they 'beat' as they interfere with each other).

I know of no way to disable specific tracks in a multitrack movie 
loaded into SMIL (apart from exotic Wired Sprites).

> Steven, can you give Jeremy your presentation or take the snapshots 
> yourself? that would help the overall quality feeling.

They are in place now.

> It seems like pre-buffering is interrupted between the various 
> slides.... I wonder if this is a quicktime problem or not. Maybe is 
> there a way to tell quicktime not to stop buffering between slides.

There is a QuickTime extension to SMIL that asks the player to 
instantiate everything before it starts playing .... it makes no 

Unfortunately, I think the primary cause of this problem will be likely 
be to do with how the audio and video data is interleaved in the .avi 
file. (Not such a problem when the whole file is already on disk, in 
which case this SMIL plays fine). In QuickTime, they have the concept 
of a 'fast-start' movie, which I believe, means it is specially 
interleaved to allow efficient playback while the download in in 

Extremely painful as this may seem =:-0
We may need to experiment with different encoding techniques for these 
to play in QT.

> [btw, can you windows folks check if the above works with quicktime 
> for windows as well? thanks]
> I also noted that if you remove the quicktime-namespaced extentions, 
> it still works.
>>>> So maybe the DivX codec is not so good after all :)
>>> divx is the most crossplatform/free codec, that's why I choose it, 
>>> nothing about technical excellence in the choice. It had to be "good 
>>> enough".
>>> I'm not surprised if it doesn't work well with more interactive 
>>> usage.... have you tried with real player?
>> Not yet ....

Did anyone try the RealSMIL version of the introduction yet?
Did any Widows users with QuickTime try the QuickTimeSMIL?


>>>> OK, so I could re-process the video so it would maybe work, but the 
>>>> whole idea was to re-use the existing files in different >>>>
>>> yep.
>> See what milage you get ..... I have hard-coded one of the UK Mirrors 
>> as the source of the movie .... if we can get this to work, we need a 
>> way of sending you off to your local mirror.
> I'm full bandwidth with that mirror anyway, so it's pretty good.
> Note that we might be able to do automatic redirection to the closest 
> mirror, just like geoip-based URL redirection. shouldn't be much 
> different from the mirror.cgi we already have
> (and this is how we'll do block distribution with the librarian)

I'd love to know how ....

regards Jeremy

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