[FFmpeg-devel] MPEG-PS demuxer index memory usage
Fri Jan 4 18:50:22 CET 2008
On Fri, Jan 04, 2008 at 05:50:01PM +0100, Michel Bardiaux wrote:
> Michael Niedermayer a ?crit :
> > On Thu, Jan 03, 2008 at 10:48:49PM +0000, Paul Kelly wrote:
> >> Hello
> >> I'm using libavformat to demux a continuous stream of MPEG2-PS data and am
> >> running into the problem that memory usage steadily increases over time.
> >> The problem is not observed when demuxing an MPEG2-TS stream.
> >> After a bit of digging around I discovered the problem is caused by the
> >> timestamp indexing in the PS demuxer - specifically, the calls to
> >> av_add_index_entry() in mpegps_read_pes_header() in libavformat/mpeg.c.
> >> All I'm doing is transcoding the stream to a different output format and I
> >> don't need to be able to perform seeking but there doesn't seem to be any
> >> way to disable the index. (I guess the memory occupied by the index isn't
> >> a problem if a fixed-size file is being demuxed, but in my case I am
> >> reading data from a hardware MPEG encoder card and splitting the output
> >> into separate files and the process is required to run indefinitely - the
> >> index quickly grows to an unwieldy size.)
> >> As far as I can see the flag AVFMT_GENERIC_INDEX can be turned off to stop
> >> indexing if generic indexing is used (perhaps that's a non-standard usage
> >> though) - but is there no way to turn off the indexing in the MPEG-PS
> >> demuxer?
> >> Might it be a good idea to add another flag to turn off the
> >> demuxer-specific indexing, and make individual demuxers respect this? A
> >> general catch-all way of disabling indexing (or specifying that seeking
> >> isn't required) might be more elegant though.
> >> I can get over the immediate problem by simply commenting out the line
> >> calling av_add_index_entry() in libavformat/mpeg.c, but would like to help
> >> get a better solution into libavformat if I can.
> > Disabling it with a flag is surely interresting. But i think there are better
> > solutions.
> > One for example would be a max_index_size. And when thats reached index
> > entries would be pseudo randomly droped. That would limit the used memory and
> > still speed up seeking.
> Another possibility (not exclusive):
> if(!url_is_streamed(s->pb)) av_add_index_entry(...)
> After all, if the input is streamed, the index is unlikely to be of any use!
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
I have often repented speaking, but never of holding my tongue.
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