[Libav-user] decoding speed on large files

Marco Gulino marco.gulino at gmail.com
Thu Oct 17 17:48:17 CEST 2013

To be more clear: I need to extract text subtitles from large files, saving
them on a database.
I am currently able to reencode the subtitle itself, but the decoding part
( http://pastebin.com/WbJwAKFx )  is really damn slow, while "ffmpeg"
command line takes just a few seconds.
Is there anything I'm missing? Custom IO? Frames skipping?

On Tue, Oct 1, 2013 at 11:25 AM, Marco Gulino <marco.gulino at gmail.com>wrote:

> Hello
> I'm noticing a huge difference in decoding speed with my own code, and
> with ffmpeg command line tool, especially with large (> 2GB) files.
> This is my current test code: http://pastebin.com/WbJwAKFx
> Just looping over the packets, without even reading them, takes 120
> seconds.
> When I run "ffmpeg -i mylargefile.mp4 /tmp/extractedSubtitle.srt", it
> takes no more than 10 seconds. Of course, I dropped linux kernel caches
> first, to force the same file reading speed.
> I tried looking at ffmpeg.c, but I didn't notice anything in particular.
> Thanks
> Marco
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