[mythtv] A need for advanced player settings

Mark Kendall mark.kendall at gmail.com
Tue May 31 03:37:58 UTC 2011

On 31 May 2011 11:25, Kyle Rose <krose at krose.org> wrote:
>> Apologies for the late response. Can you provide a link where we can
>> download the problematic file? From memory, matroska doesn't take well
>> to being clipped randomly so I'm assuming it will need to be the whole
>> thing.
> I took a 750MB prefix of the file in question, which seems to play
> fine. Here it is (for the next 72 hours):

Thanks - downloading now.

>> 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.

Thanks and regards


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