[mythtv-users] Playback problem -- random short pauses

Michael T. Dean mtdean at thirdcontact.com
Mon May 23 19:51:01 UTC 2011


On 05/23/2011 03:20 PM, Steven Adeff wrote:
> On Mon, May 23, 2011 at 3:06 PM, Daniel Kristjansson wrote:
>> Removing the fsync() call can lead to pauses, in the unlikely event that
>> it is being called on a Linux system. The fdatasync() and range syncs
>> are mostly no-ops since we're appending to a file, so removing those
>> will have no effect. The main reason the fsync() was added was to
>> prevent pauses on when the disk I/O scheduler decided to finally write
>> hundreds of megabytes of data to disk in one long write and consequently
>> starve all readers and so stop video playback. This was accidentally
>> subverted when the fdatasync() code was added. But that change happened
>> over five years ago so if you are seeing a regression with 0.24, fsync()
>> changes are not to blame.
> That's what I figured.
>
> It sounds like, from what Mike says, the issue has to do with VDPAU
> decoding and the interaction with ffmpeg (Mike, am I understanding
> that correctly?).

Yes.  (That's right for issue #2.)

>   So I don't think chasing i/o is the way to attack
> this. It sounds like Mike and the other dev's looking at the issue
> have an understanding of what's causing VDPAU to do this. Hopefully a
> solution can be found that still lets users take advantage of using
> VDPAU with ATOM-like systems.

Though this not so much--the other devs are looking into this, not me.  
I'm only relaying what info I've learned from them (and from my own 
testing that I've done, in part, for them).  :)

Mike


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