fftools/ffmpeg: simplify propagating fallback parameters from decoders to filters

Current callstack looks like this:
* ifilter_bind_ist() (filter) calls ist_filter_add() (demuxer);
* ist_filter_add() opens the decoder, and then calls
  dec_add_filter() (decoder);
* dec_add_filter() calls ifilter_parameters_from_dec() (i.e. back into
  the filtering code) in order to give post-avcodec_open2() parameters
  to the filter.

This is unnecessarily complicated. Pass the parameters as follows
instead:
* dec_init() (which opens the decoder) returns post-avcodec_open2()
  parameters to its caller (i.e. the demuxer) in a parameter-only
  AVFrame
* the demuxer passes these parameters to the filter in
  InputFilterOptions, together with other filter options

1 files changed, 6 insertions, 3 deletions

diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index d3e03543ac..1a60f035b0 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -259,6 +259,8 @@ typedef struct InputFilterOptions {
 
     // a combination of IFILTER_FLAG_*
     unsigned            flags;
+
+    AVFrame            *fallback;
 } InputFilterOptions;
 
 typedef struct InputFilter {
@@ -735,16 +737,17 @@ AVBufferRef *hw_device_for_filter(void);
 /**
  * @param dec_opts Dictionary filled with decoder options. Its ownership
  *                 is transferred to the decoder.
+ * @param param_out If non-NULL, media properties after opening the decoder
+ *                  are written here.
  *
  * @retval ">=0" non-negative scheduler index on success
  * @retval "<0"  an error code on failure
  */
 int dec_init(Decoder **pdec, Scheduler *sch,
-             AVDictionary **dec_opts, const DecoderOpts *o);
+             AVDictionary **dec_opts, const DecoderOpts *o,
+             AVFrame *param_out);
 void dec_free(Decoder **pdec);
 
-int dec_add_filter(Decoder *dec, InputFilter *ifilter);
-
 int enc_alloc(Encoder **penc, const AVCodec *codec,
               Scheduler *sch, unsigned sch_idx);
 void enc_free(Encoder **penc);