[mythtv-commits] Ticket #2984: Enhancement for finding MPEG2 startcodes
MythTV
mythtv at cvs.mythtv.org
Wed Jan 24 17:01:43 UTC 2007
#2984: Enhancement for finding MPEG2 startcodes
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Reporter: gnome42 at gmail.com | Owner: ijr
Type: enhancement | Status: new
Priority: minor | Milestone: unknown
Component: mythtv | Version: 0.20
Severity: medium |
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Two patches to speed up finding start codes in MPEG2 streams. One patch
for recording (dtvrecorder) and one for playback (avformatdecoder).
I did some micro benchmarks comparing three scanning methods; the current
one-byte-at-a-time approach, memchr(), and this three-btyes-at-a-time
approach. I was expecting the memchr() to be the fastest but three-bytes-
at-a-time always seemed to be quicker.
Sample output from a run on an old celeron:[[BR]]
Found 13437824 matches in 42.4915 seconds (three-bytes ...)[[BR]]
Found 13437824 matches in 54.9326 seconds (memchr())[[BR]]
Found 13437824 matches in 96.6009 seconds (one-byte ... current)
Problem: These patches both use nothl() for endian issues, this is
undesireable. :/ But Janne says he has a way around this? :)
Also, I think danielk has said that these scanning methods are 'naive' and
could be improved. If anyone has some pointers or hints on how to do that
I would be interested.
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Ticket URL: <http://cvs.mythtv.org/trac/ticket/2984>
MythTV <http://www.mythtv.org/>
MythTV
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