[mythtv-users] Intel i965 video buffers errors on frontend

[Stuart Auchterlonie]

On 10/07/17 10:58, evade. wrote:
> On 06/07/17 23:35, Stuart Auchterlonie wrote:
>> On 06/07/17 12:35, evade at internode.on.net wrote:
>>> Hello,
>>> I'm having difficult problems with playback in the frontend version
>>> 0.28.1-3 and would love some help please!
>>>
>>> Intel H170M chipset, Intel i5-6500 CPU with HD Graphics 530
>>>
>>> <snip>
>>> So I switched to VAAPI, despite it lacking deinterlacing.  I'm still
>>> having playback problems with stuttering, especially with live TV.  My
>>> PC also has Intel HD audio (Realtek ALC892).
>>>
>>> Although playback works, when I enable debug logging I see multiple
>>> occurrences of both:
>>>
>>> <date> <time> I  Player(0): Waiting for video buffers...
>>>
>>> and:
>>>
>>> <date> <time> I  Player(0): Video is 3.54437 frames ahead of audio,
>>>                          doubling video frame interval to slow down.
>>>
>>> <snip>
>>
>> When playing back the recording pull up the playback data screen
>> (m > playback > playback data)
>>
>> and have a look at the data there. It's a little complex, but
>> you need to check a few things.
>>
>> - cpus usage, check it's not maxed out
>> - storage to buffer and buffer to decoder figures.
>>    You want storage to buffer figures to be significantly higher than
>>    the buffer to decoder figures (not just a little bit higher)
>> - available buffer. this figure is upside down, should really say "used
>>    buffer", the closer to 100% this is the better.
>> - frames decoded / free, frames decoded really should be greater than 10
>>    for consistent viewing.
>>
>>
>> Regards
>> Stuart
> 
> Thanks for the fast response Stuart!
> 
> 
> My CPU has 4 cores and no hyperthreading.  I'm testing with 1080i H.264
> broadcast TV, because that's the worst-case scenario where I am.
> 
> When the problem occurs the first core sits at about 75% and there's 0%
> of 4 Mb buffer available!  Sometimes after 10 to 20 seconds playback
> freezes momentarily.  Then the buffer jumps up to 20% and the first core
> averages around the same as the other cores at under 15% utilisation.
> (I imagine that the 75% utilisation involves a lot of I/O wait due to
> the buffer being empty.)

This cpu usage indicates that the cpu is doing the decoding,
in the status screen it probably also said "ffmpeg" rather than "vaapi"

> 
> The other figures are:
>> 1 Gbps (!)  Storage To Buffer

Good

> up to 5 Mbps  Buffer to Decoder
> and
> Frames decoded / free
> ~3/~18
> 

Okay, it's not decoding enough frames, i'd expect because it's using
the cpu and not the gpu to do the decode.

So check your profiles, to ensure it's selecting vaapi for this content.

> 
> If I start playback, then immediately pause and wait 10 seconds, I can
> get the buffer up to 60%, but the problem is this means jumping TV
> channels isn't an option!  (I imagine my spouse will not tolerate it)
> 
> 
> For the record, I bought the i5-6500 CPU hoping it's GPU would not have
> any problems as I intend to run two small KVM VMs on the system also.
> (They use SSD storage, totally separate from the HDDs where mythtv is
> writing and reading from)
> For this reason I'm not content going back to software rendering, even
> if it works.
> I may be wrong, but I thought the 'OpenGL' playback profile was software
> based, which is why I've tried VDPAU and now VAAPI.

This cpu with it's embedded gpu should be able to handle this content


Regards
Stuart


> 
> Thank you,
> evade.
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