bugGnash - The GNU Flash player - Bugs: bug #26928, Stuttering media playback due to...


bug #26928: Stuttering media playback due to blocking reads when parsing

Submitter:  Benjamin Wolsey <bwy>
Submitted:  Wed 01 Jul 2009 08:22:05 AM UTC
Category:  None Severity:  3 - Normal
Release:  None Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open
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Tue 06 Jul 2010 03:06:28 PM UTC, comment #3: 

Daniel, are you using gstreamer or ffmpeg media handler of Gnash ?

Sandro Santilli <strk>
Group Member
Tue 06 Jul 2010 02:47:53 PM UTC, comment #2: 

Is this the reason for the following playback issue with megavideo? I observe this:

The video is loaded in background. Seeing the load bar I see that a sufficient amount of video is loaded and keeps on loading. However the playback stalls every few seconds (as in 10-20sec) saying "Buffering: " and a number of percentage. This is reproducible on two systems and different videos of megavideo.
Once the video is fully preloaded it works and plays smoothly. Please let me know if this is caused by the problem described by bwy, otherwise I can open a separate report. Thanks!

Daniel Michalik <argafal>
Thu 24 Sep 2009 10:54:59 AM UTC, comment #1: 

What's the problem with the media parser thread blocking
if there's nothing to read ?

Maybe some lock not being released ? Which one ?

Sandro Santilli <strk>
Group Member
Wed 01 Jul 2009 08:22:05 AM UTC, original submission:  

Some videos, often on youtube, get frequent pauses while waiting for data.

The cause is that seek() and read_byte() both do blocking reads. If one of these calls happens to require more data in the cache, the media thread blocks until data is recieved and the video pauses.

These are called from various places in FLVParser.

Changing IOChannel::read_byte() to call readNonBlocking() and CurlStreamFile::seek() to call fillCacheNonBlocking() (though it does not take a 'pos' argument) results in a much smoother playback (no pauses), but a different download pattern.

Benjamin Wolsey <bwy>
Group Member


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    Follows 1 latest change.

    Date Changed by Updated Field Previous Value => Replaced by
    2009-07-28 bwy SummaryMedia parsing blocks Stuttering media playback due to blocking reads when parsing

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