[FFmpeg-devel] [PATCH 4/4] mmaldec: limit internal buffering

[wm4]

On Wed, 27 Jan 2016 20:41:33 +0100
Michael Niedermayer <michael at niedermayer.cc> wrote:

> On Wed, Jan 27, 2016 at 05:17:56PM +0100, wm4 wrote:
> > This uses a new MMAL feature, which limits the number of extra frames
> > that can be buffered within the decoder. VIDEO_MAX_NUM_CALLBACKS can
> > be defined as positive or negative number. Positive numbers are
> > absolute, and can lead to deadlocks if the user underestimates the
> > required buffers. Negative numbers specify the number of extra
> > buffers, e.g. -1 means no extra buffer, (-1-N) means N extra buffers.
> > 
> > Set a gratuitous default of -11 (N=10). This is much lower than the
> > firmware default, which appears to be 96.
> > 
> > This is backwards compatible, but needs a symbol only present in newer
> > firmware headers. (It's an enum item, so it requires a check in
> > configure.)
> > ---
> >  configure            | 4 ++++
> >  libavcodec/mmaldec.c | 7 +++++++
> >  2 files changed, 11 insertions(+)
> > 
> > diff --git a/configure b/configure
> > index 9b195c9..e5f513b 100755
> > --- a/configure
> > +++ b/configure
> > @@ -5546,6 +5546,10 @@ enabled mmal              && { check_lib interface/mmal/mmal.h mmal_port_connect
> >                                      check_lib interface/mmal/mmal.h mmal_port_connect ; }
> >                                  check_lib interface/mmal/mmal.h mmal_port_connect ; } ||
> >                                 die "ERROR: mmal not found"; }
> > +enabled mmal &&
> > +    check_code cc interface/mmal/mmal.h "MMAL_PARAMETER_VIDEO_MAX_NUM_CALLBACKS" ||
> > +    die "ERROR: mmal firmware headers too old"
> > +
> >  enabled netcdf            && require_pkg_config netcdf netcdf.h nc_inq_libvers
> >  enabled nvenc             && { check_header nvEncodeAPI.h || die "ERROR: nvEncodeAPI.h not found."; } &&
> >                               { check_cpp_condition nvEncodeAPI.h "NVENCAPI_MAJOR_VERSION >= 5" ||  
> 
> this or a previous change breaks build
> make distclean ; ../configure --cc='ccache x86_64-w64-mingw32-gcc' --arch=x86_64 --target-os=mingw32 --cross-prefix=x86_64-w64-mingw32- && make -j12
> ERROR: mmal firmware headers too old
> 
> 
> [...]

Thanks for catching it. I'll change it to:

enabled mmal &&
    (check_code cc interface/mmal/mmal.h "MMAL_PARAMETER_VIDEO_MAX_NUM_CALLBACKS" ||
     die "ERROR: mmal firmware headers too old")

This should work, shouldn't it?