[FFmpeg-devel] [PATCH] AAC fatetests
Sat Jul 10 22:56:12 CEST 2010
On Sat, Jul 10, 2010 at 09:53:23PM +0100, M?ns Rullg?rd wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> > On Sat, Jul 10, 2010 at 10:44:45PM +0200, Michael Niedermayer wrote:
> >> On Sat, Jul 10, 2010 at 09:39:29PM +0100, M?ns Rullg?rd wrote:
> >> > Michael Niedermayer <michaelni at gmx.at> writes:
> >> >
> >> > > On Sat, Jul 10, 2010 at 11:49:41AM +0200, Reimar D?ffinger wrote:
> >> > >> On Sat, Jul 10, 2010 at 10:24:26AM +0100, M?ns Rullg?rd wrote:
> >> [...]
> >> > >> This would also allow testing of non-seekable input without needing
> >> > >> http or piping from stdin...
> >> > >
> >> > > one cant seek in bz2 ?
> >> > > did gnu butcher the _block_ based bw transform that much?
> >> >
> >> > There is likely no way to find the block boundaries other than by
> >> > decoding the entire thing.
> >> if so that would be a very lame design, because the basic algorithm doesnt
> >> use the previous blocks being able to recover in case of damage would
> >> have been a nice feature
> > tfm says:
> > RECOVERING DATA FROM DAMAGED FILES
> > bzip2 compresses files in blocks, usually 900kbytes long. Each block
> > is handled independently. If a media or transmission error causes a
> > multi-block .bz2 file to become damaged, it may be possible to recover
> > data from the undamaged blocks in the file.
> > The compressed representation of each block is delimited by a 48-bit
> > pattern, which makes it possible to find the block boundaries with rea-
> > sonable certainty. Each block also carries its own 32-bit CRC, so dam-
> > aged blocks can be distinguished from undamaged ones.
> > bzip2recover is a simple program whose purpose is to search for blocks
> > in .bz2 files, and write each block out into its own .bz2 file. You
> > can then use bzip2 -t to test the integrity of the resulting files, and
> > decompress those which are undamaged.
> > so my assumtation that one should be able to seek in bz2 is not all
> > that wrong
> Yes, it seems that it should be possible, albeit with some overhead
> scanning for startcodes and with only 900k granularity.
bzip2 seems to support it down to 100k blocks, this would though require
files to be created with the intent to be more seekable and would cost
some compression rate
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Into a blind darkness they enter who follow after the Ignorance,
they as if into a greater darkness enter who devote themselves
to the Knowledge alone. -- Isha Upanishad
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