ffmpeg: exporting RTP header extension via packet side data

Exports RTP header extension as base64 encoded side data of type AV_PKT_DATA_STRINGS_METADATA. --- ffmpeg-4.2.7/libavformat/rtpdec.c 2022-05-13 23:07:14.000000000 +0000 +++ ffmpeg-4.2.7-patched/libavformat/rtpdec.c 2024-12-28 12:40:26.348880247 +0000 @@ -23,6 +23,7 @@ #inclu…