[FFmpeg-devel] [PATCH 1/3] ffmpeg: Don't print graphs if there are no graphs to print

[softworkz .]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Mark
> Thompson
> Sent: Samstag, 17. Mai 2025 20:19
> To: ffmpeg-devel at ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH 1/3] ffmpeg: Don't print graphs if there
> are no graphs to print
> 
> On 17/05/2025 18:52, softworkz . wrote:
> >
> >
> >> -----Original Message-----
> >> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Mark
> >> Thompson
> >> Sent: Samstag, 17. Mai 2025 13:14
> >> To: ffmpeg-devel at ffmpeg.org
> >> Subject: [FFmpeg-devel] [PATCH 1/3] ffmpeg: Don't print graphs if there are
> no
> >> graphs to print
> >>
> >> Avoids writing an empty json blob in setup error cases.
> >> ---
> >>  fftools/ffmpeg.c | 3 ++-
> >>  1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
> >> index 964770df23..ad28cff78d 100644
> >> --- a/fftools/ffmpeg.c
> >> +++ b/fftools/ffmpeg.c
> >> @@ -309,7 +309,8 @@ const AVIOInterruptCB int_cb = { decode_interrupt_cb,
> NULL
> >> };
> >>
> >>  static void ffmpeg_cleanup(int ret)
> >>  {
> >> -    if (print_graphs || print_graphs_file)
> >> +    if ((print_graphs || print_graphs_file) &&
> >> +        (nb_filtergraphs > 0 || nb_output_files > 0))
> >>          print_filtergraphs(filtergraphs, nb_filtergraphs, input_files,
> >> nb_input_files, output_files, nb_output_files);
> >
> > The feature is not just about filter graphs, that's why it's been renamed
> > as "Execution Graph Printing". It also works when no filter graphs are
> > in play at all.
> > Here's an example:
> >
> > https://softworkz.github.io/ffmpeg_output_apis/1_nofilters_3_in_1_out.html
> >
> >
> > As for the nb_output_files check, I'm not sure - is it 0 or 1 in case of
> > -f null output?
> 
> 1, including when you stream copy to null and there aren't any real graphs.
> At least one output is mandatory for a valid command line, so it should always
> appear in non-error cases as far as I am aware.
> 
> The aim is to avoid to the nonsense json blob when an early error happens -
> example below.  It does still get printed on later errors (such as a muxer
> error), because the graph is created then and some operations will have
> happened at that point.
> 
> Thanks,
> 
> - Mark

Okay, thanks for the clarification, and yes - it's important to get the output
even in cases of error, but I agree that it doesn't need to be generated
as long as output files haven't been configured yet.

If you could resubmit without the nb_filtergraphs check that would be fine!

Thank you
sw