[Matroska-devel] Re: Re: EBML

[Martin Nilsson]

Paul Bryson wrote:
> When deciding which compression method would be best for
> storing VobSubs, Mosu tested not only the encoding and decoding speed of
> different libraries, but also how well they handled errors.  Even if a method is
> technically better, existing libraries my make a different method more
> practical.

I know that Opera made a PNG library of their own last year, reducing 
the size from 160K to 5K. It is fast enough to decode images on mobile 
phones. So most of these issues can be solved if you are determined to, 
e.g. by working closer to developers of other technology. But again, I 
have no problems to see why this hasn't been done.

> Limiting the number of subtitle formats definately wouldn't decrease the size of
> the lib.  Subtitles are just another generic form of data in Matroska. > The 
same as Video and Audio.  Its all generic.  Matroska doesn't care > what 
it is, it depends on whatever system is being used to decode the > data 
in the proper way.

The reason why I mentioned subtitles in the first place is beacuse there 
is some sort of interpretation of the formats when separating them into 
Track->CodecPrivate and Cluster->Block. Since there is interpretation, 
why not also have normalization, or at least "compression" to a binary 
format? One could note that the segmentation of SSA files didn't help us 
with our video player, since our SSA decoder worked on complete SSA 
files. Skip to specific words in the subtitles are also a more costly 
operation now that you have to seek through more data.

But I guess that I am talking for no reason. The "correct" solution from 
Matroska point of view is for me to present a new format and hope for 
its adoption.

> On a different note, PNG would be very desireable with its 255 levels of alpha.
> Current systems are not strong enough to be depended on to decode PNG subtitles
> without causing a pause in the video.

You can't be referring to systems made this century...

> Also, it is not likely that any will ever provide full UTF-8 support as the full
 > Arial font is around 20MB.

As always it's a matter of competence. You can get a Unicode font 
supporting all languages, optimized for TV-resolution, from Bitstream 
that is around 3MB. You can cluster that one into codepages and compress 
them separately.

/Martin Nilsson