[vlc-devel] [PATCH 0/1] Improve SFTP network performance with buffer

Martin Disch martindisch at gmail.com
Sat Feb 17 15:24:24 CET 2018

On Sat, Feb 17, 2018 at 2:18 PM, Ilkka Ollakka <ileoo at videolan.org> wrote:

> Ah, Martin, would it be possible to check if same issue appears with
> current sftp module if you remove cache_read module from stream-filters?
> cache_block/read and prefetch seem to overlap on functionality and not
> sure if cache-module is usable on cases where fast_seek is enabled (it's
> the case where prefetch is refusing to load and cache goes to
> cache_read/cache_block module to my understanding).

Sure thing! To clarify what you want me to do exactly I have three questions:

1. By "the issue" do you mean the slowness of SFTP reading I described
in the first place, or the fact that the stream prefetch filter
doesn't help unless its read size is increased in the options?

2. Concerning the stream filters, I noticed something I can't make
sense of. There's the options page where all available filters are
listed with checkboxes. Checking one of them adds the module name to
the text box below, which I assume is used as an argument telling VLC
which stream filters to use. The stream prefetch filter is the only
one of them offering its own options. When I went and increased the
buffer size, I realized that the change took effect (VLC used more
memory to accommodate the buffer), even though I did not check the
checkbox for the stream prefetch filter (= add "prefetch" to the text
box). Does the stream prefetch filter activate itself because I
changed its settings, or is it (and by implication all of the other
stream filters) active by default? I can't imagine that's the case.

3. By "remove cache_read", do you mean not have it activated in the
stream filters settings I mentioned before, or build VLC s.t. it is
not there at all? Because if it's the former, I never had the
cache_read filter activated anyway. I only ever used prefetch on its
own or nothing at all.

Regardless of what you meant, I did both:

- Since I never had the byte stream cache (cache_read) active, it's
safe to say that the issue has nothing to do with that (assuming it
really is not active unless activated by me).
- To be sure, I also excluded cache_read from the build by running a
make clean, commenting the two lines for cache_read in the
stream_filter makefile and building again (I checked, the byte stream
cache option was gone from the list of filters afterwards). No change
in behavior, prefetch with default settings doesn't help with the
problem and only by setting the read size to something like 262144 can
I get VLC to use enough bandwidth to keep up with the bitrate of the

Martin Disch
martindisch at gmail.com

More information about the vlc-devel mailing list