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

[Rahul Lodha]

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?