[mythtv-users] Little OT: RealTime Parallel Multi-PC Transcoding
belcampo at zonnet.nl
Wed Jun 16 16:38:39 UTC 2010
Raymond Wagner wrote:
>>> You would want the video cuts to be tens of seconds long to reduce
>>> data and startup overhead.
>> Could you be more specific on this ?
> Starting up processes is expensive. The startup and teardown of
> something complex like x264 is probably going to be a couple seconds.
> If you're only going to be encoding chunks of a couple seconds long,
> that is a huge amount of overhead.
The original whole-file transcode takes 262 seconds for 1523 frames
The 34 chunks transcode takes 254 seconds, but only 1400 frames remain.
How counterintuitive it is/may look the chunk approach is on encode-time
per frame faster by 5%
The odds that are happening:
Split bbchd.ts on every 2 seconds with tsMuxeR.
Chop the 34-chunks with tsMuxeR into a new bbchdnew.ts and I do get a
perfect playing file with exactly the same amount of frames.
Every individual file is correct and complete. Playing the individual
files with a PopCornHour is 100% glitch-free.
After encoding, with ffmpeg, the 34chunks and stitching them together
again with tsMuxeR, results in slightly unsmooth, because of the missing
frames, and 4-times little glitches/blockiness.
Conclusion so far:
No indications for huge amount of overhead because of the chunks.
Running it with 6Cores it completes in 44seconds being 595% but with
8.78% less frames, leaves a total score of 547% being 91% per core
performace which is much better than any multithreading approach I have
seen so far.
But, ffmpeg should be able to pick all chunks as 100% valid which it
doesn't seem to be able.
Please comment/suggest/flame or whatever.
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