[FFmpeg-devel] [PATCH] Configure graph filters with more than one output

[Stefano Sabatini]

On date Saturday 2009-05-30 20:56:16 +0200, Vitor Sessak encoded:
> Stefano Sabatini wrote:
>> Hi all,
>>
>> I'm experimenting with a graph chain of this kind:
>> ffplay in.avi -vfilters "split [out] [select], [select] select='eq(mod(N, 10), 0)', snapshot"
>
> I suppose you mean
>
> ffplay in.avi -vfilters "split [out] [select]; [select] select='eq(mod(N, 10), 0)', snapshot"
>
> (note the ';')

It's equivalent to the previous syntax in this specific case.

> or
>
> ffplay in.avi -vfilters "split [out]  select='eq(mod(N, 10), 0)', snapshot"

This is wrong syntax.
stefano at geppetto ~/s/l/ffmpeg>  ffplay in.avi -vfilters "split [out]  select='eq(mod(N, 10), 0)', snapshot"
FFplay version SVN-r18854, Copyright (c) 2003-2009 Fabrice Bellard, et al.
[...]
Unable to parse graph description substring: "select='eq(mod(N, 10), 0)', snapshot"

>
> ?
>
>> the problem is that the config_props of the snapshot is never called,
>> since the code which do the configuration:
>>
>>  if(avfilter_config_links(filt_out))                      goto the_end;
>>
>> only configure the part of the graph from the application output
>> filers towards the beginning.
>>
>> Suggested function call avfilter_config_links(filt_out) on all the
>> output filters of a graph (that is filters which one input and no
>> output).
>
>> +int avfilter_graph_config_links(AVFilterGraph *graph, AVClass *log_ctx)
>> +{
>> +    AVFilterContext *filt;
>> +    int i, ret;
>> +
>> +    for (i=0; i < graph->filter_count; i++) {
>> +        filt = graph->filters[i];
>> +
>> +        if (!filt->output_count) {
>> +            if ((ret = avfilter_config_links(filt)))
>> +                return ret;
>> +        }
>> +    }
>
> Hmmm... I'm fine with the patch, but I think this makes the  
> recursiveness of avfilter_config_links() useless.

Why?

avfilter_config_list() recursiveness works in the direction from an
output link towards all the connected sources in input, but you need
to call it on each output if you have a graph with more than one
output.

> Since it doesn't work for the example you've given, I'd say it
> should be removed (but it can be another patch).

I really cannot understand this, should we keep it or should we remove
it, what is not working?

Regards.
-- 
FFmpeg = Faithful and Fantastic Most Portable Ephemeral God