[mythtv-users] [ALSA] "Skipping" arround a show causes an Abort (or segfault).

David George david at thegeorges.us
Sat Aug 21 20:51:25 EDT 2004


David George wrote:

> John Patrick Poet wrote:
>
>> When using "pure" ALSA via my S/PDIF connection for audio, I get
>> segfaults/aborts in the ALSA code if I "JUMP/SKIP" arround in the video
>> very much.  I am using ALSA 1.0.5 since ALSA 1.0.6 has audio glitches.
>>
>> If I use OSS emulation, the Aborts/Segfaults do not happen, but I get
>> several seconds of stuttering after a JUMP/SKIP which I do not get with
>> "pure" ALSA.
>>
>> The crashes do not happen on every SKIP forward/backward, but they do
>> happen often.  With one particular show, I can consitantly cause a crash
>> by doing a dozen 30 second forward skips quickly, and then a couple of 6
>> second skips backwards.
>>
>> I have attached a BackTrace in the hopes that someone can figure out
>> what is going wrong.
>>
> Still digesting all this.
>
> Quick question, are you using 4k stacks in the kernel, because 
> AudioOutputAlsa::OutputAudioLoop is allocating 4k worth of zeros on 
> the stack.  I will change that to malloc and send a patch in a little 
> bit.

Yes, before anybody corrects me, I know this affects kernel stack 
allocation (i.e. kernel drivers) and not user space.  I guess I am old 
school and just don't like to declare automatic variables that large.

--
David



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