[gstreamer-bugs] [Bug 320820] Investigate on the usage of -DRUNTIME_CPUDETECT

[GStreamer (bugzilla.gnome.org)]

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 GStreamer | gst-ffmpeg | Ver: HEAD CVS





------- Comment #5 from Loïc Minier  2006-01-15 16:35 UTC -------
Andy, the flag would be useful for a part of ffmpeg, but does not cover all
usages of CPU-specific assembly.  Details follow.


In general, building gst-ffmpeg on a CPU might create binaries that require a
CPU with at least the same capacities, but this is often undesired for
distribution (where buildd machines are fast CPUs but you want the binaries to
run on all machines supported for that arch and that dist).

The libpostproc part is #ifdef'd so that by default libpp will be optimized at
build-time, the suggested flag moves the optimization to runtime.  Other parts
than libpp are not #ifdef and are unconditionally build time optimized.

This is especially a problem under PPC.

Now I initially opened this bug because I thought -DRUNTIME_CPUDETECT was
enough for the whole of ffmpeg, and thought it would make more sense for it to
be the default.  Since the autotools-ization of gst-ffmpeg is written by
GStreamer, this was discussed here.  However, my assumption turned out to be
false, and this could be considered a ffmpeg bug for the ffmpeg project to deal
with first.

I'll let you decide whether this bug should stay open as a reminder that
gst-ffmpeg does not generate portable PPC binaries by default, nor can be
configured to do so.

Cheers,


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