[vlc-devel] Figured out streaming issues and why youtube works better than VLC player

Rémi Denis-Courmont remi at remlab.net
Mon Oct 18 11:26:39 CEST 2010

On Mon, 18 Oct 2010 01:13:11 -0700 (PDT), Tony Anecito
<adanecito at yahoo.com> wrote:
> Thanks for the quick response. I verified that youtube is storing the
> video by deleting my internet explorer temp files then when replaying
> the video the lighter red progress bar in the middle of the slider is
> gone when first playing the video and if I did not delete the temp
> internet files the light red bar in the middle of the slider is present
> and spans the entire length of the slider in the youtube page.

I don't see that behavior on my platform. And I would argue it is entirely
irrelevant because:
1/ VLC cannot rely on HTTP content caching on the first playback of a given
2/ The user can save the file manually if (s)he intends to play it again
and again.
3/ Network operators can use an HTTP proxy if they expect many users to
view the same video on a given network.

Given this, HTTP caching is way too intricate for very minimal benefits to
ever be implemented in VLC.

> How do I increase the size of the input stream buffer from within vlc 1.5

> luggage dated 2010 10/18? Are you talking about the http cache time?

No. I wrote the STREAM cache and I meant the STREAM cache. The buffer sizes
are set in src/input/stream.c. Currently, it's 4 megabytes.

> Also you mention a recent VLC update yet I have the latest vlc nightly. I
> did notice in the area of the QT4 GUI when vlc is running where rate
> time is displayed that it seems to get a background progress color when
> seems to re-buffer after a pts issue.
> I am thinking to default values of VLC after an install are great for
> files and smaller streaming videos but with HD or HQ streaming they
> will not work very well.

Yes and no. VLC purposefully expresses caching in terms of PTS/time
duration rather than in data size. That's precisely so that caching is
independent of the media bandwidth. Hence, the ES output buffers size will
be proportional to the bandwidth, which is exactly what you seem to ask
ES buffer size = Bandwidth * PTS delay, where PTS delay is a constant.

And with that said, I don't think tuning http-caching or the stream cache
size parameters specifically to your computer will help VLC in any
meaningful way. If you want to improve network congestion handling, you
really need to dig into the dirty details of the input synchronization and
caching algorithm. And that in turn, would require a decent unit tests
suite to avoid regressions.

Rémi Denis-Courmont

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