[mythtv-commits] Ticket #7935: [PATCH] Improve MPEG-TS seeking performance by 60X

[MythTV]

#7935: [PATCH] Improve MPEG-TS seeking performance by 60X
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 Reporter:  taylor.ralph@…           |       Owner:  janne
     Type:  patch                    |      Status:  new  
 Priority:  minor                    |   Milestone:  0.23 
Component:  MythTV - Video Playback  |     Version:  head 
 Severity:  medium                   |     Mlocked:  0    
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 I've recently discovered that slow seeking for MPEG-TS using av_seek_frame
 is caused by inefficient handling of EOF in libs/libmythtv/RingBuffer.cpp.
 The attached patch addresses the following issues:

  * Inside safe_read() we need to break after a read() if it's an "oldfile"
 (>30 minutes). There is no reason to delay (60000 usec) and retry for this
 case. The calling code will retry anyways if ret > 0 and if ret == 0 then
 it really is the EOF.

  * When an lseek is performed we need to adjust the totfree buffer amount
 before entering a 50000 usec delay. Every time an lseek is performed the
 buffer gets reset so we should update totfree before checking to see if
 the buffer it full and we need to wiat.

 One other issue I believe is that 30 minutes is too long to determine if a
 file is an "oldfile". I'd like to see that reduced to a more reasonable
 value and if possible add a better check to determine it the file is open
 for writing.

 Without this patch applied an av_seek_frame takes ~0.9 secs and with the
 patch it takes ~0.015. This will also improve performance for other
 containers as well.

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Ticket URL: <http://svn.mythtv.org/trac/ticket/7935>
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