[FFmpeg-devel] [PATCH] swresample: Use channel count in rematrix initialization

Marcin Gorzel gorzel at google.com
Tue Jul 24 16:55:08 EEST 2018


On Mon, Jul 23, 2018 at 7:52 AM Michael Niedermayer <michael at niedermayer.cc>
wrote:

> On Sat, Jul 21, 2018 at 07:31:12PM +0100, Marcin Gorzel wrote:
> > Rematrixing supports up to 64 channels. However, there is only a limited
> number of channel layouts defined. Since the in/out channel count is
> currently obtained from the channel layout, for undefined layouts (e.g. for
> 9, 10, 11 channels etc.) the rematrixing fails.
> >
> > This patch changes rematrix init methods to use in/out channel count
> directly instead of computing it from channel layout.
> > ---
> >  libswresample/rematrix.c          | 4 ++--
> >  libswresample/x86/rematrix_init.c | 4 ++--
> >  2 files changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/libswresample/rematrix.c b/libswresample/rematrix.c
> > index 8227730056..ec1909dc0c 100644
> > --- a/libswresample/rematrix.c
> > +++ b/libswresample/rematrix.c
> > @@ -384,8 +384,8 @@ av_cold static int auto_matrix(SwrContext *s)
> >
> >  av_cold int swri_rematrix_init(SwrContext *s){
> >      int i, j;
> > -    int nb_in  = av_get_channel_layout_nb_channels(s->in_ch_layout);
> > -    int nb_out = av_get_channel_layout_nb_channels(s->out_ch_layout);
> > +    int nb_in = s->in.ch_count;
> > +    int nb_out = s->out.ch_count;
> >
> >      s->mix_any_f = NULL;
>
> This is much better than the previous patch
> still, why is this not using used_ch_count ?
>
> Lets look at the code in swresample.c, as i dont remember 100% ...
> First stage is in_convert, its initialized with:
> s->in_convert = swri_audio_convert_alloc(s->int_sample_fmt,
>                                              s-> in_sample_fmt,
> s->used_ch_count, s->channel_map, 0);
>
> You can see here that used_ch_count is its output
> and next stages are resample and rematrix (in either order)
>
> how can they have s->in.ch_count as input ?
>
> and yes, it seems there is no testcase that catches this, which is
> unfortunate.
>

I think you are right, looking at the swresample.c again, used_ch_count is
initially obtained from the user_used_ch_count. In the case
user_used_ch_count is not set (default: 0) used_ch_count will take the
value of in.ch_count. I've changed that.

Also, OOC, shouldn't used_ch_count be used for s->resample_first in
swresample.c:321 as well in this case?

a much more minor issue is, please vertically align the "=" as it was
> before the patch.
>

Done.

Thanks
>
> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> The educated differ from the uneducated as much as the living from the
> dead. -- Aristotle
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-- 

Marcin Gorzel |  Software Engineer |  gorzel at google.com |


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