[vlc-devel] [PATCH] dvdnav: add Demux submodule

Luca Barbato lu_zero at gentoo.org
Wed Mar 18 16:07:26 CET 2015

On 18/03/15 15:47, Thomas Guillem wrote:
> When opening a DVD, libdvdread was doing a lot of read of 2kB and a lot
> of seek at the same position. Mainly because the same part of the IFO
> was read from different context (but still from the same thread). In
> order to workaround this issue, I put in cache the IFO file (that is
> 128kB max), so now there is only one read of 128kB per IFO.
> I also did some test with and without the readahead_flag. With this flag
> (enabled by default for all except OS2), the read size is between 4OOkB
> and 500kB but I have seen few reads of 850kB after a seek. Without this
> flag, the read size is always 2kB.
> I don't know which flag is a better for a net access. Is it better to
> have less but bigger read accesses or more but smaller read accesses ?
> I also simulated a very long read, 1 second to read 100kB. I didn't see
> any issues expect that there was a lot of buffering pause.
> So I fail to see the difference between the dvdnav demux and any other
> demux regarding I/O.

The problem I'm seeing is only in net_Read and should impact all the 
demuxers I think.

If those are the numbers I wouldn't consider it a problem. (Large would 
be 50MB to me)

Would be nice to timeout on net_Read instead of polling until the end of 
time (if I read that code right), but seems unrelated to this patch.


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