[MPlayer-dev-eng] container format

[Christof Buergi]

Am Donnerstag, 6. Februar 2003 19.30 schrieb Michael Niedermayer:
> hmmmm, i think u missunderstand the checksum slghtly, the idea is
> that u download a file somehow from somewhere ;) after or during the
> download  u notice that its damaged (by checking the checksum, or
> seeing the image break into ugly blocks, ...) after that u redownload
> the damage parts from somewhere else, all that could be automatic or
> manual, but it only works if we can check the file, yes decoding
> everything to detect errors is possible to but its slower and more
> complex

I get shivers when I try to imagine having to code this. But yes, the 
idea is nice. ;-)

Still, there are situations where CRC-checks make no sense at all. In 
those situations, the person doing the encoding might get the idea to 
shut down checksums and get those extra bits to encrease bandwith. The 
downside of making checksums optional, however, is the possibility of 
badly coded files increasing, thus lowering the reputation of the 
container. It also slightly increases complexity.

> yes, fec is nice, but i dont see why this should be included in the
> fileformat, IMHO a idependant format like gzip would be better,
> actually iam working on that since some time :)))) but i have too
> many other things to do

Well, yes. It might be a better idea to put this in a special network 
protocol. After all, http is not really suited for live streams.

> > Second point are some small suggestions about indeces. I think, we
> > should place the index at the end of the file. Having it at the
> > beginning would be nice for playback, but it would be a nightmare
> > to correctly mux this.
> IMHO, we could allow both, and even allow the index to be repeated

But Indeces are not that important in this container format, are they? 
Still, it may indeed be a good idea to let the muxer decide, where (if 
at all) he wants to place the index.

> > Also, gzip might actually be a better joice here
> > then bzip2. But this is a matter to try.
> the index is <10kb per hour, IMHO its not worth to g/bzip it

Good point. Still, it might be noticeable on audio-only files. However, 
since indeces are not really needed, most audio-only files will be 
encoded without index anyway, I guess.

> VLC means "variable length coding", it means that the individual
> fields/variables like width & height are not encoded with a constant
> number of bits

Ah, now I see. Being heavily influenced by the world of big computers 
(S/390 etc.), I interpret some terms a bit different.

PS: I'll be away for a week. Up up in the alps and skiing. ;-)

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