[OpenIndiana-discuss] Comments, please! problem with ffmpeg that seems to be a problem with OI at driver or basic library level

[Hans J. Albertsson]

I just discovered that with most Ubuntu versions and recent ffmpegs, the 
same hang happens there.

So it isn't just OI.

Good. Or bad.. Or something. I will look into it, trussing and whatever. 
I mean my ffmpeg is locally compiled and I have the source code for 
reference.

On 2013-05-15 16:05, Bob Friesenhahn wrote:
> On Wed, 15 May 2013, Hans J. Albertsson wrote:
>
>> I regularly download ( quite legally, I'm told ) HLS streams from 
>> svtplay.se using ffmpeg and a stream URL obtained by scraping the 
>> svtplay.se/<show-link> page.
>>
>> This works very well in Ubuntu and Windows on a separate PC.
>>
>> Under OI and even in W XP inside a VirtualBox VM it hangs, seemingly 
>> at random positions in the stream. The ffmpeg process is totally 
>> inert upon hanging, and one must kill it by two consecutive ^C. It 
>> doesn't respond to the on the fly command language at all.
>>
>> The hang is in pollsys, as demonstrated by the following truss -f 
>> output excerpt from the hanging ffmpeg process.
>>
>> 29961:    pollsys(0x08046768, 1, 0x08046718, 0x00000000)    = 0
>> 29961:    pollsys(0x08046768, 1, 0x08046718, 0x00000000)    = 0
>> 29961:    pollsys(0x08046768, 1, 0x08046718, 0x00000000)    = 0
>> 29961:    pollsys(0x08046768, 1, 0x08046718, 0x00000000)    = 0
>> 29961:    pollsys(0x08046768, 1, 0x08046718, 0x00000000)    = 0
>> 29961:    pollsys(0x08046768, 1, 0x08046718, 0x00000000)    = 0
>> 29961:    pollsys(0x08046768, 1, 0x08046718, 0x00000000)    = 0
>> 29961:    pollsys(0x08046768, 1, 0x08046718, 0x00000000)    = 0
>>
>>
>> I guess that the fact it happens in the W XP in vbox the same as in 
>> OI itself indicates the problem somehow involves code residing under 
>> the Vbox VM, even, and that it's some sort of incompatibility that 
>> only will actually have an effect under some sort of race or 
>> race-like condition.
>>
>> I'd appreciate any insight any of you could offer into what this entails
>
> I see similar issues with the VLC player which decides that 'mplayer' 
> is too slow and not able to keep up.  Without taking time to diagnose, 
> my first guess would be a buffering issue which causes the hang.  The 
> software is developed under Linux and may have certain buffering (e.g. 
> pipe buffering) expectations. Confusion between the buffering and any 
> locking (or even just the buffering) might cause a deadlock in the 
> software.
>
> To diagnose, try using 'pstack' on the processes which are hanging and 
> see where they are hung.
>
> Bob