[FFmpeg-devel] [RFC][PATCH] Windows Television (WTV) file system handling

Peter Ross pross
Tue Jan 11 03:01:48 CET 2011

On Tue, Jan 11, 2011 at 12:33:59AM +0100, Michael Niedermayer wrote:
> On Sun, Jan 09, 2011 at 05:21:20PM +1100, Peter Ross wrote:
> > Hi,
> > 
> > The Windows Television (WTV) file format is a more complex beast than
> > initially imagined.
> > 
> > WTV is best viewed as a file system. Metadata, seek index tables, and
> > chunked data are stored in separate files within. The fileystem uses
> > a simple hierarchical file allocation table, with standard (4k) and big
> > (256k) sector sizes. Standard FAT concepts apply, like fragmentation
> > and the existence of slack space.
> > 
> > The current WTV demuxer is not aware of the file system, and therefore
> > only works on smalls wtv samples (<600MiB) where the files are not
> > fragmented. Most WTV recordings are much larger. e.g. a 3hr HD recording
> > of the tennis results in a 24GiB file and lots of fragmentation.
> > 
> > Due to the complexity, I would really appreciate comments on the patch,
> > especially my use of ByteIOContext.
> Which part of the ByteIOContext use do you want comments about?

wtvfile_read_packet(), wtvfile_seek() and wtv_open_sector() if possible.

These functions provide a ByteIOContext instance, representing the contents
of a file within the filesystem.

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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