[FFmpeg-devel] libavfilter: avfilter_graph_parse2 is not preserving pad names

[Paul B Mahol]

On 7/14/20, Rahul Lodha <rahullodhas at gmail.com> wrote:
> I wrote a code to mix two audio streams which is working. However,
> somehow `avfilter_graph_parse2` is not preserving the pad names
>
> For example, below is a filter spec
>
> ```
> filter_spec =
> "abuffer=time_base=1/48000:sample_rate=48000:sample_fmt=fltp:channel_layout=0x3[a0]
> ;
> abuffer=time_base=1/48000:sample_rate=48000:sample_fmt=fltp:channel_layout=0x3
> [a1];
>  [a0] [a1] amix=inputs=2, abuffersink";
> ```
> Below is the code to parse and dump graph
>
> ```
> if ((ret = avfilter_graph_parse2(filter_graph, filter_spec, &inputs,
> &outputs)) < 0) {
>                 av_log(NULL, AV_LOG_ERROR, "avfilter_graph_parse_ptr
> failed: %d\n", ret);
>         }
>
>         if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0) {
>                 av_log(NULL, AV_LOG_ERROR, "avfilter_graph_config
> failed\n");
>         }
>
> char *g = avfilter_graph_dump(filter_graph, NULL);
>         if(g) {
>                 av_log(NULL, AV_LOG_ERROR, "Graph: %s\n", g);
>                 av_free(g);
>         }
>
> ```
> and below is the graph dump.
>
> ```
> Graph: +------------------+
> | Parsed_abuffer_0 |default--[48000Hz fltp:stereo]--Parsed_amix_2:input0
> |    (abuffer)     |
> +------------------+
>
> +------------------+
> | Parsed_abuffer_1 |default--[48000Hz fltp:stereo]--Parsed_amix_2:input1
> |    (abuffer)     |
> +------------------+
>
>                                                        +---------------+
> Parsed_abuffer_0:default--[48000Hz fltp:stereo]--input0| Parsed_amix_2
> |default--[48000Hz fltp:stereo]--Parsed_abuffersink_3:default
> Parsed_abuffer_1:default--[48000Hz fltp:stereo]--input1|    (amix)     |
>                                                        +---------------+
>
>
> +----------------------+
> Parsed_amix_2:default--[48000Hz fltp:stereo]--default| Parsed_abuffersink_3
> |
>                                                      |    (abuffersink)
> |
>
> +----------------------+
>
>
>
> ```
>
> As you can see, all the pad names a0, a1, etc gone and they are
> replaced by `default`, Parsed_abuffersink_3 etc.
>
> Is there any way to preserve names?

Such pad names are never preserved.
Could they be preserved? Certainly yes. Patch welcome.

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