[MPlayer-users] Containers, GMC, PSNR, and doom9

[Alexander Noe']

Ivan Kowalenko schrieb:

>> [1] http://forums.virtualdub.org/index.php? 
>> s=8558dbc13f1fdb67454c5aca0e529d39&act=ST&f=2&t=11828&hl=stream +numbers
> 
> 
> I stand corrected. The thing that confused me (and still does) is  that 
> every time someone comes on the mailing list with an AVI file  with a 
> subtitle track in it, they're told that the file is a hack,  and they'll 
> need to extract the subtitle stream.  If AVI has no  problem with 
> subtitles, as stated above, then what is the story with  those "hacked" 
> files? I'm genuinely curious.

Those files are kinda badly designed: There is one big subtitle chunk 
for an entire stream, containing a SSA or SRT file, which is contrary 
to the concept of a "stream".

The AVI specification is a bit lousy here because it says that you can 
put subtitles into a ##tx chunk, but doesn't really define what a 
subtitle block inside an AVI file looks like. The idea was probably to 
make up "subtitle codecs" one day, like you could imagine to put SSA 
headers in STRF and create a format tag for it. Since Gabest was the 
first one to actually make use of this possibility, it's he who 
finally decided to do it this way, but appearently forgot to write it 
down. When I added support for that in AVI-Mux GUI, I had to PM him to 
get that information.

The best way for mplayer to support that would probably be to map the 
chunk containing the entire subtitle stream into a memory-mapped file 
and run it through a subtitle file parser, treating it as external 
file. I guess this best way is not considered good enough...



Alex


-- 
„Der Horizont vieler Menschen ist ein Kreis mit dem Radius
Null – und das nennen sie dann ihren Standpunkt. (Albert
Einstein)“