[FFmpeg-devel] [PATCH] avfilter/formats: set audio fmt lists for vaf filters

[Niklas Haas]

From: Niklas Haas <git at haasn.dev>

Currently, the logic inside the FF_FILTER_FORMATS_QUERY_FUNC branch
prevents this code from running in the event that we have a filter with
a single video input and a single audio output, as the resulting audio
output link will not have its channel counts / samplerates correctly
initialized to their default values, possibly triggering a segfault
downstream.

An example of such a filter is vaf_spectrumsynth. Although this
particular filter already sets up the channel counts and samplerates as
part of the query function and therefore avoids triggering this bug, the
bug still exists in principle. (And importantly, sets a wrong precedent)
---
 libavfilter/formats.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/libavfilter/formats.c b/libavfilter/formats.c
index d1c97daf64..114886aeb2 100644
--- a/libavfilter/formats.c
+++ b/libavfilter/formats.c
@@ -808,16 +808,17 @@ int ff_default_query_formats(AVFilterContext *ctx)
     /* Intended fallthrough */
     case FF_FILTER_FORMATS_PASSTHROUGH:
     case FF_FILTER_FORMATS_QUERY_FUNC:
-        type    = ctx->nb_inputs  ? ctx->inputs [0]->type :
-                  ctx->nb_outputs ? ctx->outputs[0]->type : AVMEDIA_TYPE_VIDEO;
-        formats = ff_all_formats(type);
+        type = AVMEDIA_TYPE_UNKNOWN;
+        formats = ff_all_formats(ctx->nb_inputs  ? ctx->inputs [0]->type :
+                                 ctx->nb_outputs ? ctx->outputs[0]->type :
+                                 AVMEDIA_TYPE_VIDEO);
         break;
     }
 
     ret = ff_set_common_formats(ctx, formats);
     if (ret < 0)
         return ret;
-    if (type == AVMEDIA_TYPE_AUDIO) {
+    if (type != AVMEDIA_TYPE_VIDEO) {
         ret = ff_set_common_all_channel_counts(ctx);
         if (ret < 0)
             return ret;
-- 
2.43.0