[vlc-devel] Dropped frames despite ample CPU idle time?

Devin Heitmueller dheitmueller at kernellabs.com
Wed Jun 12 20:17:09 CEST 2013

On Wed, Jun 12, 2013 at 11:57 AM, Finn Hughes <finn.hughes1 at gmail.com> wrote:
> That's some fast reply ;)
> If I disable the subtitles or switch to yadif deinterlacing I do not drop
> frames which AFAIK may discount:
> "It could be that the decoder outputs corrupt timestamps, or the packetizer,
> or the demuxer, or the source media."
> If so I guess that leaves
> 1. excessive jitter
> 2. video output renders too slowly
> 3. input synchronization or decoder code
> Although maybe 3 is also unlikely based on the above?
> An additional note is that frames are only being dropped when the subtitles
> are being updated, which to my mind makes 1. the likeliest option, is there
> an obvious way to try to isolate the problem area?

I've actually got some patches coming down the pipeline which may very
well address this issue.  Was having similar problems with high
bitrate MPEG2 streams and EIA-608 closed caption rendering.  In the
end I introduced support for FreeType font caching as well as needing
to adjust the buffering for a couple of the different source types
(there was I/O contention because the file source type only does
read() calls of around 2K, which is really bad when trying to read a
15Mb/s stream).

I cannot say for certain that they will fix your use case, but they
definitely helped in mine (going from losing around 5% of the video
frames to zero).

Stay tuned.


Devin J. Heitmueller - Kernel Labs

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