[mythtv] A need for advanced player settings

[Mark Kendall]

On 31 May 2011 11:37, Mark Kendall <mark.kendall at gmail.com> wrote:
>>> This does tie into some issues that a couple of people have been
>>> trying to debug in the last couple of weeks. There was a suggestion of
>>> incorrect bitrate detection and/or updates with one file and it
>>> obviously ties up with the symptoms.
>>
>> Does Matroska store the maximum bitrate of a variable bitrate stream
>> anywhere? That would be sufficient information to solve this
>> particular problem, but I don't know enough about Matroska.
>
> I've been doing some digging and it seems not (and that seems to be a
> design policy).
>
> From testing with another problematic file, my gut feeling is that the
> root cause is the bitrate detection in AvFormateDecoder::ScanStreams.
> For the broken files, the H264 bitrate is detected as zero and there
> is a long standing hack to force that to 500000bps (line 1751 in
> master). I was hoping that forcing that to something much higher would
> fix playback and, while not being a long term fix, would prove the
> point.  Unfortunately, it didn't...
>
> Which either suggests I'm completely wrong or there is some additional
> complexity I've missed.

Looking again at the code, it's clear that getting the bitrate correct
isn't going to change the behaviour much. As you've already figured
out, the key variables are already hard coded.

I think however the problem is another manifestation of an issue I've
been trying to figure out with dvd and and bluray playback over
storage groups - both of which have sizeable speed/performance issues.

In master/pre-0.25, video playback will always use direct access to
local files if they are local. Your file and the other I've been
testing both suffer from repeatable pauses on my remote frontends but
if I NFS mount the video directories, the frontend thinks they're
local and opens them over nfs - and they both play without a problem.
This also fixes dvd playback.

So my current thinking is that the increased buffer size is just
masking some inefficiency/performance issue with the remote file
access.