[Mplayer-dev-eng] Re: Re: Re: [Mplayer-users] bugs?

[Christoph Lampert]

Hi Arpi!

On Tue, 31 Jul 2001, Arpi wrote:
> Hi,
>
> > Doesn't sound too bad. However, I still have a problem with the file: It
> > plays for 3 or 4 minutes (after -idx skipping there is possible), then stops
> > with message  "file doesn't contain the selected audio or video stream"
> >
> > I know the file is broken, but: Is this repairable?
> yes, everything is repairable. even a broken HDD driver with ntfs partition
> containing very important data -> but should be done manually -> lots' of
> money :)
>
> if you send me teh file & money, i'll hack it with hex editor and get it
> work :)
>
> ok. stop joking:)
> i don't know any program or method for automatically fix broken avi files.
> avi is the worst file format i've ever seen. it has zero error tolerance.

Yes, I know... And I pity you for having to always answer the same
questions :-) I really didn't want you to write an omnipotent AviFix program
(although... maybe... no, mplayer is more important ;-)

I was just wondering (same with the other files, that said "no video
stream"), since this does not seem to be a broken downloads (because
several file show same behaviour) but wrongly written header, that you
maybe had an idea how to "cure" this.
E.g. the file I wrote about seems to look for another video stream,
although it already started to play one. I find that strange, but on
the other hand, I know nothing about AVI (and am happy to admit that).

Well, I'll just keep loading, one day, non-broken files will show up :-)

gruel


P.S. I checked it, this was the longest mail I ever got from A'rpi :-)

> for example, asf and mpeg-ts files are from constant-length blocks, so
> if a block is broken, you can skip it and read next (you know where is it).
> for mpeg, there are sync codes (0x0 0x0 0x1), so it's easy to resync.
> same for mpeg audio, but sync code is something like f3ffxxxx, i duno now,
> but you can check in mp3lib/sr1.c resync method.
>
> for avi, you have nothing.
> it has variable sized chunks, each chunks contains its length.
> if a chunk is broken, you don't know where is the next and you don't know
> is it broken or not...)
>
> i can imagine a brute-force method (but should be impemenetd in a standalone
> util prog, not in mplayer):
> if teh parser thinks that chunk is broken (too large chunksize, or invalid
> chunk id), it can recursive call itself (parser), and try to find next
> chunk probing each byte position after the buggy chunk. if it's ok, try to
> check next chunk if still ok, then we can skip broken chunk.
> it isn't 100% perfect, and can fail for good chunks and pass broken chunks,
> but may help in most cases (or not, didn't try).
>
> i personally hate the avi file format, and really hope thay people will
> change to something more usefull (mpeg/asf/quicktime).
>
> and i forget to saym but you already noticed: A-V sync in avi files is
> terrible.. there is only one standard way (in avi file format specification)
> but nobody uses it (i have only oen file using this, it's about 5 years old,
> using CRAM codec...). it specifies that audio-video chunk pairs should be
> defined in a LIST item.
>
> currently there are 3 formats, none of them is standard.
> 1. interleaved streams: same as standard, but they left out LIST chunks,
>    only list A and V and A and V etc after eachother.
> 2. bps method: audio and video streams are totally independent (usually
>    -ni streams), but audio timestamp can be calculated by dividing audio
>    byte position by a 'average bytes per second' value specified in audio
>    stream format header. it can't handle VBR audio.
> 3. combination of 1. and 2. i just got such file, it's Lola Rennt german
>    dvdrip version (thanx Atmos :)).
>    it plays with mplayer using method 1., but you can't seek (lost A-V
>    sync if seeking). i'ev found that avifile handle this file, because it
>    uses combination of 1. and 2. methods (at least fersh avifile 9.6 cvs).
>    i'll implement this and try, mayeb help for some special streams.
>    btw there are some streams (about 5% of all) which works with mpalyer's
>    method 1., but fails with avifile's mixed method 3.
>    windows media player uses something between 1. and 3., couldn't find
>    yet how it works. old avifile and mplayer -bps uses method 2.
>
> i really don't know, what are standards made for?
> but i'm sure, m$ doesn't know too.
>
> sorry for being offtopic, this should go to mplayer-dev-eng.
>
> > "Epsilon < 0" - chl
> is it standard? =)
>
>
> A'rpi / Astral & ESP-team
>
> --
> mailto:arpi at thot.banki.hu
> http://esp-team.scene.hu
>
> _______________________________________________
> Mplayer-users mailing list
> Mplayer-users at lists.sourceforge.net
> http://lists.sourceforge.net/lists/listinfo/mplayer-users
>

-- 
Dipl. math. Christoph Lampert (complex analysis, integral formulae)

Gibraltargatan 86                  |     CTH, Matematiskt centrum
rum 637                            |     Eklandagatan 86, rum 2235
41279 Gothenburg                   |     41296 Gothenburg
SWEDEN                             |     SWEDEN
Email: gruel at gmx.de                |     Email: lampert at math.chalmers.se
                                   | 	 Tel. +46 31 772 5323 (office)


_______________________________________________
Mplayer-dev-eng mailing list
Mplayer-dev-eng at lists.sourceforge.net
http://lists.sourceforge.net/lists/listinfo/mplayer-dev-eng